MECHANISTIC STUDIES IN REACTIONS

OF ALLYLIC COMPOUNDS

A thesis presented by

MIJWAFAK YASSIN SHANDALA

in partial fulfilment of the requirements

for admittance to the

DOCTOR OF PHILOSOPHY

IN THE

UNIVERSITY OF LONDON

Linstead Laboratory, Chemistry Department, Imperial College, London, S.W.7. June, 1964. ABSTRACT

The general properties of allylic compounds, the work

on and 3- phenylallyl chlorides and p-nitrobertoates and the the effect of a substituent on the reactivity of/side chain in

benzene ring are reviewed.

MeChanistic studies on the solvolytic reactions of

1- and 3- phenylallyl chlorides with a substituent in the

phenyl ring have been carried out. The effect of the substituent

on the reaction mechanisms are discussed.

Studies on the reaction of 1- and 3- phenylallyl

chlorides with lithium radiochloride have shown that the

exchange of 1-phenylallyl chloride with lithium radiochloride

occurs more slowly than the loss of optical activity of the

(-)-isomer and is identical to the rate of racemization under

the same conditions. The isomerization of 1-phenylallyl

chloride and some substituted chlorides under non-solvolytic

conditions have also been carried out.

The isomerization of substituted 1-phenylallyl p-

nitrobenzoate in non-hydroxylic solvents have been studied;

in the light of the results obtained possible mechanisms are

discussed.

Unsuccessful attempts have been made to prepre some

1-phenylallylamines by various routes. TO MY FATHER iv.

ACKNOWLEDGEMENTS

This work was carried out under the supervision of

Dr. E. S. Waight, to whom I am grateful for his constant and generous help.

I am deeply indebted to Professor D. H. R. Barton, F.R.S., for giving me the opportunity of working in the Organic Chemistry

Department of Imperial College.

I also wish to thank Dr. D. W. Turner for his advice and useful discussion on the tracer work.

The m±croanalytical determination were carried out by the staff of the Microanalytical Laboratory, under Miss J.

Cuckney; the N.M.R. spectra were run by Mrs. A. I. Boston.

I wish to acknowledge my indeptedness to all of these, and to my colleagues in the Organic Chemistry Department for many helpful discussions.

Finally, I would like to thank my family for their financial support and encouragement which made my university education possible.

V.

CONTENTS Pau Review 1 - 38

I. General properties of allylic compounds

II. Phenylallyl system 6

A. Phonylallyl chlorides Cinnamyl chlorides 7 1-Phonylally1 Chloride 10

i - Preparation 10

ii - Isomerization= 11

iii - Solvolysis 14

iv - Reaction with amines 18

v - Racemization 21 36 vi - Exchange reaction with C1

B. Isomerization of 1-phenylally1 p-

nitrobenzoate 24

III The effect of substituents on the reactivity of the side chain in benzene ring. 31 Results and Discussion. 39 - 129

I Solvolysis of substituted cinnamyl chlorides 40

II Solvolytic reactions of 1-phenylallyl

chlorides 72 III Isomerization of 1-phenylallyi chlorides 95 IV Rearrangement of 1-phenylallyl p-nitro-

benzoates 118 vi.

Contents (Contd/...)

Page

V Attempts to prepare 1-phenylallylamines 124

Experimental 130 - 177 Preparation 131

Solvents 154 Salts 157

Kinetics 160 Examples of kinetic run 169 References 178 REVIEW 2.

I - General Properties of Allylio Compounds

Allylic compounds are those organic substances which can be represented by structure (I), i.e. those organic compounds having an ethylenio linkage a1 /9 to a carbon atom bearing an eleotro-negative functional group such as Cl, Br, I, OR, OR, or OCCR, or an eleotropositive group such as MgX, Li, Na, or g. The functional group is activated by the ethylenio linkage. For this reason allylio compounds undergo displacement reactions more readily than the analogous saturated compounds, e.g. 3-methylallyl chloride reacts 95 times faster than n-butyl chloride with ethenolic sodium ethoxide at 44.6° 1. Allylic compounds undergo rearrangement to isomeric substances whioh can be represented by struature (II). Reactions

R R1 0 = C R2 • C R3 R4X -1...R R1 X C - C C R3R4 I II of this type are known as allylio rearrangements. The term anionotropy introduced by Ingold2 refers to molecular rearrangements in which the anion is the migrating group. The term was redefined by Braude3 as the migration of an anion or other group together with its bonding eleotrons. The equilibrium in an aniontropio system can be eonsidered quite independently of the mechanism of the rearrangement. The 3.

equilibrium mixture of oinnamyl and 1-phenylally1 chlorides contains no detectable quantities of the latter:

100$ Ph.CH CH.CH2X, Ph.CHX.CH : CH2 Oro

The composition of the equilibrium mixture between crotyl and 1-methylallyl chlorides and between the corresponding bromides4:

(75-e5) cH3.cH : CH.CH X 2 cn .CHX.CH : CH2 (15-20%

depends on, the halide, the temperature and the solvent. The speoial term oxotropy is used for an ionotropio rearrangement involving only the migration of hydroxyl group, corresponding to the term prototropy foroationotropio rearrangement in which the migrating group is hydrogen. Isomerization reactions of allylio alcohols, esters and ethers have been reviewed by Braude5'5 Solvolytio reactions of allylio compounds can be broadly classified as being either unimolecular or bimolecular and in addition there is a large group of reactions which do not fall under either heading and are sometimes called border-line reactions. There is the additional possibility of rearrangement accompanying the solvolysis of allylio compounds. In allylio systems undergoing SO displacements, methyl substitution at the reacting centre causes a rate decrease of the same magnitude as in the saturated systems; e.g. 4c-methyl-allyl chloride is less reactive than allyl chloride by a factor 20 towards ethoxide ionl, i.e. in the 1- position, substituonts, whether electron-releasing or -withdrawing retard the reaction by steno interference with approach of nucleophilic reagents. y-Alkyl substituents increase the rate and y-halogen substituents also generally cause a rate increase in direct substitution, ie. electron- releasing substituents on the 3-carbon atom of the allylio system facilitate the direct displacement by assisting the departure of the leaving group as a negative ion. 0-Halogen substituents show rate decreases which are assooiated predominantly with their induotive effect. It has long been known6'7'8 that electron-releasing substituents on both the 1- and 3- carbon atoms of the allylio system greatly increase the rate of unimoleoular displacement reactions probably by facilitating the ionization step and by stabilizing the resulting carbonium ion, while a chlorine substituent on either the 1- or the 3- carbon atom of allyl chloride causes a small increase in the rate. A number of examples of reactions of substituted allylic system are quoted in a review by Young and DeWolfe on the 5 0

substitution and rearrangement reactions of allylic compounds9, and in a review by Streitwieser on the solvolytio displacement rea ction at saturated carbon atoMs10. 6.

II - Phenylallyl System A.Phenylally1 ohlorides

The two isomers of phenylallyl chloride are particularly suitable compounds for the study of the isomerization and solvolytic reactions. This system presents several advantages, compared with simple alkyl allylic systems, which can be summarized as follows: i) In the primary isomer (IV) the allylic system is conjugatedwiththe benzene ring and in the secondary isomer (III) it is not. The styryl chromophore has high absorption intensity at about 2500 R. Cinnamyl chloride and its normal solvolysis products absorb light at 2530 E with a molecular extinction coefficient (i) of about 18,000, while for the 1-phenylallyl compounds 6 is about 200 at the same wave length. Reactions of phenylallyl halide are thus conveniently followed by observing the intensity at 2530.1?.. The final value together with titrimetric determination of acid or halide ions formed are sufficient to give a complete analysis of the products without the necessity of isolating the products or even removing the solvent.

ii) The secondary isomer (III) is much more reactive

(in S1 reactions) than the primary, so that the solvolysis of the form= is not complicated by concurrent reaction of any of 7.

the latter which may be formed. In the alkyl substituted primary-secondary allyl system' e.g. methylallyl chloride, the secondary isomer is only 1.6 times as reactive as the primary towards unimolecular solvolysise; in the acetolysis of 1,1- 11 12' dimethylallyl chloride ' the 3.,3 isomer is formed but reacts with solvent at rate similar to the tertiary isomer...... En.CH(OS)CH=r0H2it (III) Ph.CHO1.CH=CH2 ----> Ph.CH2m=CH.CH2C1 (IV) 14( CS Ph.CH=CH.CH2 iii) The optically active 1-phenylallyl chloride can be 13 prepared and study of its racemization gives further information on the intermediates involved in the solvolysis and rearrangement reactions.

Oinnamyl chloride

Cinnamyl chloride is a well-known compound and it has long been known 15'16 that the reaction5- of cinnamyl halides can give rise to a mixture of allylic isomers. 1 8 Vernon ' has investigated kinetically the reaction of oinnamyl chloride with absolute and aqueous ethanol, measuring the rate of formation of acid or of 'biocide ions. He concluded that the solvolysis is unimolecular in the more ionizing aqueous 8.

solvent, but showed a tendency towards bimolecularity in absolute ethanol. Vernon also found that the rate of ethanolysis of cinnamyl chloride was greatly increased by the addition of ethoxide ions in pure solvents but that the rate of solvolysis in aqueous solvent was virtually independent of added hydroxide ions. On the basis of these investigations the solvolysis of oinnamyl chloride must be included among those reactions regarded as "border-line", appearing to be unimolecular in solvents of high ionizing power but to have some bimolecular character when the conditions are favourable, ie. in solvent of low or moderate ionizing power in the presence of strong nucleophiles.

The mechanism of the solvolysis of cinnonyl chloride was 17 re-examined by Valkanas ; he obtained rate constants for the solvolysis in ethanol and 60% aqueous dioxan and noted the effect of added salts containing anions of differing nucleophilicities. He was able to estimate the amount of rearrangement by using the final u.v. light absorption. 18 Weinstock repeated some of Valkanas work. He obtained the rate constants, and analysed the solvolysis products of cinnaxnyl chloride, in 70, 60, 50, 40 and 50% aqueous dioxan and in 98, 90, 80, 70 and 60% ethanol-cyclohexane. He also studied the effect of added NaOH and salts. Recently Valkanas, Weight and 9.

Weinstock19 published their results suggesting that an ion-pair is formed in the rate determining step without nucleophilic assistance by the solvent. In the most highly aqueous media the counter ions are sufficiently well separated before reaction with solvent for the positive charge to be completely delocalized, so that the isomeric products are obtained in about the same ratio as from the free carbonium ion, In less highly ionizing media, water reacts when the chloride ion is stil closer to the 3-carbon atom that to the 1-carbon atom, so that the oarbonium ion is polarized with positive charge localized at the 3-position and more cinnmtyl alcohol is formed. • 1. Ph-CH = CH-CH2C1;41Ph-CH .. CH-CH2 Cl fast fast H2O 6+ 5+ H2O Ph.CHTFICH2 + Cl Pb CH R CH - CH 0H + HC1 - 2 Cl fast fast t H2O

+ HC1 Ph.CH(OH)- CH = CH2

Ethanolysis,of cinnamyl chloride, they suggested, requires nucleophilic assistance by solvent in the rate determining step, or the ooncurrence of unimolecular and bimolecular meohansims. 10.

HOEt slow Cil Ph - CH o CH - CH2C1 kt7=7:h.CH . CH - CH2 fast f"-b1 Et0H fast IfOt • • fast Ph - CP2LICHACH ""'"""'"`k Ph. CH . CH - CH OEt + HC1 „ 2 EtOH 2 ,4 Cl fast [ EtCH

Ph - CHOEt.CH - CH2 + HC1

1 Phenylallyl Chloride. (i) Preparation The preparation of 1-phenylally1 chloride by Valkanas and Waight20 Involved reaction of 1-phenylally1 alcohol and thionyl chloride either in ether in the presence of tri-n-butyl amine or in chloroform in the presence of triethylamine. Previously Martin and Trinh21 claimed that they obtained a small yield of 1-phenylallyl chloride by repeated fractionation of the product obtained by passing dry hydrogen chloride into either 1-phenylallyl alcohol or oinnamyl alcohol. The product had a refractive index n n2 0 1.5274 which was much lower than that reported by Valkanas and Waight. Young and his co-workers22 claimed a quantitative conversion of cinnamyl alcohol to 1-phenylally1 chloride by the action of thionyl chloride in 0.1 M ethereal solution, but did not record the properties of their U.

produCt. Braude; Vali-Inas and %light" on repetition Of the above method Under the same conditions obtained a mixture containing at least 45% of cinnamyl chloride before dietillationi Recently 24 Rawlinson and Noyes in their work on the salt effect on the rearrangement of 1-phenylallyl chloride reported that the preparation of 1-phenylally1 chloride according to the method of Valkanas and

Weight gave low yields in their hands. They had better success with the procedure of Young et al. (ii) Isomerization 20 Valkanas and Waight studied the rearrangement of 1-phenylallyl chloride in solvents of widely differing dielectric constant and ionizing power. They investigated the effect of various carboxylic acids in chlorobenzene and concluded that the rate of rearrangement is increased by addition of acid, the increase being proportional to the acid concentration, and related to the strength of the acid. On this basis they suggested that one molecule of the ccia Is -,ssociated with one molecule of the chloride so that the C-Cl bond is weakened; the nucleophilicity of an undissociated carboxylic acid being much lower than that of chloride ion, the rearrangement remains essentially intra, molecular, oinnamyl esters are not formed.

12.

slow Ph.CH - CH m CH Ph.gHttl. cal!-12 2 CH2 C: HOCH Cl - H ORUC .CH:, t.:.0"N.7.: Ph.CH CH ..-...-....A Ph.CH m CH - CH2C1 •••• ,„•. 2 C1*.

23 In a preliminary note Braude, Valkanas and Waight explained the acid catalysis as involving the formation of an halonium ion as intermediate. a In the case of 01 catalysis, the possibility of/six membered ring intermediate was suggested.

HC1

Ph. CH - CH m CH 'It • IN NI MI M. •••••••••••••1016. 2-v - Ph.CH• 3:J4 CH 02,2 CH2

Ph. CR -'0H• 2 m CH - CH2C1 •Cl ,.Cl

For the isomerio rearrangement in all solvents the scheme suggested by Valkanas and. Waight was:

13.

go- e4 Ph.CH - CH Q CH2--a&Ph. CH =IL CH ""tH2 01 Cl

OEN •j.'°' Nt..1 Ph. CH CH 2 Ph.CH = CH - CH2C1 C1''

In highly polar media such as aqueous dioxan they suggested that the isomerization involved ionization of the C-Cl bond in the rate determining step. Since solvolysis occurs independently to give largely the 1-phenylallyl products the chloride and carbonium ions are evidently- separated by solvent molecules, i.e. the formation of an ion-pair of the intimate type is rate-determining. In alcoholic solvents they suggested that the ionization might involve a transition state to which covalent structures such as (V) made an important contribution.

Ph.,. ,0CH2 (v) ' • Cl'

Valkanas and Weight observed that the rate of iso- merization of 1-phenylallyl chloride in Nal-dimethylformamide increases linearly with the concentration of added lithium chloride, i.e. first order rate constants for the isomerization

14.

can be fitted by an equation di the form

m a .1- b j

where EX is the added salt. Valkanas17 suggested the following mechanistic scheme for the isomerization of 1-phenylally1 chloride in prescnoe of LiC1

Ph. CH - CH a CH ---" Ph. CH a:CH2 CH -I. Cl 01 .• .Lit

CH...... : '4. Ph. CH CH 1 : 2 Ph.CH m CH CH2C1 6;. 061 .". Li'''

LiC1 is split off with the formation of the more thermodynamically stable 3-phenylallyl chloride isomer. (iii) Solvolysis. Valkanas and Waight25 in a preliminary note on the solvolysis of 1-phenylally1 chloride stated that 1-phenylallyl chloride solvolysis products were invariably found to predominate in ratio of at least 6:1. For the solvolytic reactions of 1-phenylally1 chloride Valkanas17 suggested the following mechanistic scheme: 15.

Ph. ?H -- CH = CH2 Ph. CH -1-1 CH CH2 CI 61.- • • H • • - • CS ssk..t4. [SOH Ph. CH •0112 SOH ‘.‘ Ph.CH(OS) CH . CH2 C14 SOH [ Ph.CH . CH - CH2Cl Ph.CH CH - CH2OS

(SOH = hydroxylic solvent)

For the salt catalysis he suggested:

Solvation CH RCS + RIM at-- Ph. ,nr rearrangement •''"2 R'Cl Cl.

1 R Cl Ph.CH 1:':• CH ••:-•• CH 2 1•• • -

119 CH •% Ph. CH RI X RCS + RIGS 41. 2 Cl. .1 . • 6 M •

He stated that the solvent is less likely to associate with the double ion pair17, whioh, because of the readiness with which it 16.

can split off MC11 would preferably lead to formation of a six or four membered ring intermediates and thus to isomeric rearrange- ment. The formation of the six membered ring intermediate becomes more likely with increasing nucleophilicity of the anion of the salt and leads to rearrangement with ion exchange. The four membered ring intermediate is formed in the case of salts with anions less nucleophilic than CI and is easily solvated to give mainly unconjugated solvolysis products. 18 Weinstook re-investigated the solvolysis of 1-phenylally1 ohioride with some improvements in technique. The improvements were in: a - Purity of material. b Aocuracy of rate constant.

o Accuracy in the determination of the product composition.

Weinstock suggested the following scheme for the solvolysis of 1-phenylally1 chloride:

slow + RC1 ;=.4 Ph. CH - CH = CH2 -1. RIC1

fast 544. H20 Ph. CH 4." CH = CH2 + 01- Ph. CH.CH = CH2 + HC1 fast [ H2O OH

Ph. CH = CH - CH2OH + HC1 17.

He stated that the reaction with solvent can occur at a point where the departing chloride ion is still sufficiently close to the carbon atom whence it came to cause the positive charge to be effectively retained at that atom. The same scheme was suggested for the ethanolysis. Rawlinson and Noyes24 studied salt effects in the

isomerization of 1-phenylallyl chloride in N N-dimethylformamide at 80°, recording that the accelerating effect varies inversely with the size of the anion and is unaffected by the size of the cation. They suggested a transition state of the form

x 6 -

Ph. CH CH • 2 G.+ • ' Cl S_. wherethe anion (or ion pair), X and the migrating Cl might

share the net negative charge and be on opposite sides of the plane determined by the three allylic carbon atoms. The anion would then serve to neutralize the developing positive centre associated with chloride migration.

They also studied the isotopic exchange in N:N-dimethyl- formamide between cinnamyl chloride and tetraethylammonium chloride at 30.0° in the presence of perchlorate ion to maintain constant 18.

ionic strength, and suggested that exchange occurred by an SN2 mechanism.

(iv) Reaction with amines. Valkanas and Waightl7,26 studied the reaction of 1- and

3-phenylallyl chlorides with di- and tri-ethylamine. They reported that for 1-phenylallyl chloride in diethylamine or

triethylamine the solvolysis is accompanied by isomeric rearrange-

ment. They found that the light absorption intensity of 1- phenylallyl chloride in triethylamine initially increased, reached a maximum value which decreased with increase of temperature, and

then declined according to a first order rate law. The first

part of the reaction appeared to represent the isomeric rearrange-

ment of 1-phenylallyl chloride to cinnamyl chloride, while the second part of the reaction represented the reaction of cinnamyl chloride with triethylamine, the rate constants calculated from

the second part of the reaction agreed well with the rate

constants obtained separately from the reaction of cinnamyl chloride with triethylamine under the same conditions. I.R. and

u.v. spectra of the quaternary salt isolated indicated that about 50 of the unconjugated isomer was formed but that the latter was unstable giving the conjugated isomer.

In dimethylamine a rearrangement was observed and found to

19.

proceed to completion, i.e. to give the cinnamyl derivative. They

followed the reaction spectrometrically and titrimetrically and found that the spectrometric rate constant (k spec) exceeded the titrimetric rate constant (ktt) and both were lower than k tit for the reaction of cinnamyl chloride under the same conditions,

They suggested that isomeric rearrangement oompetes with substitution

and confirmed this by finding cinnamyl chloride in excess of the

amount originally present in the products of incomplete reaction. 17 Valkanas suggested the following scheme for the reaction of 1-phenylally2 chloride with diethylamine.

- CH. HNEto ri. G+ . Ns,: Rel.Ph,--I.,- CH L 7-1 CH LU CH2" 1"/4 --` Ph. CH CH ---*- RIM .... - ** 2 Cl i solvolysis Cl ,.,..4 RNEt RINEt 2 2 CH \ Ph. CH CH •2 N Et Et2 N,* 2

R N Et RI N Et 2 2 CH ')› Ph.CH• CH •. 1' 2 N. Et2 20.

For the reaction of cinnamyl chloride with diethylamine he suggested .NEt RIC1 + Et2NH -N-=r---=Ph.CH) = CH - CH • H HC1 2 .4 R'NEt2 Cr.

Et NH 2 NH.HC1. R1NEt2 + Et2

For the reaction of 1-phenyla11y1 chloride with triethylamine Valkanas suggested the following mechanistic scheme which is similar to that proposed for the diethylamine reaction:

NEt 3 RCI + Et3N Ph. CH 11=CH CH Ph.CH• ; 2 R.IC1 Cl If Cl solvolysis R Nitt c1 RIVEyr 3

For the reaction of cinnamyl chloride with triethylamine he suggested NEt 64 • 3 R' C1 + Et3N't....._Ph. CH CH — 9H2 N-- Ph. RI •- • RC1 solv. 61 • _ RIN+Et ci ION Et Cl +R N+Et ci 3 3 21.

(v) Racemization of optically active 1-Phenyla11y1 chloride. 27,28 Winstein and his co-workers reported that in the solvolysis reaction important evidence can be obtained for the presence of an ion-pair intermediate preceding the free carbonium

ion by comparison of the rates of racemization of optically active compounds, with their rates of reaction with solvent.

Since the chlorine atom in 1-phenylallyl chloride is attached to an asymmetric carbon atom, it is possible to prepare

the compound in the optically active form. Waight and Weinstock30,31,18 prepared (+)-1-phenylally1 chloride which, they found, racemized completely as it isomerized. In Nqi-dimethyl formamide at 40.0° or in ethanol or aqueous

dioxan at 30.0°, they found that in fact the rate of loss of optical activity k exceeded the rate of isomerisation k . rew i Under these conditions it is likely that an ion-pair intermediate is involved leading to either cinnamyl chloride ar racemic

1-phenylally1 chloride.

On the basis of the observed value of (k211.0 ktlik. i.e. from the comparison of loss of configuration at the 1-carbon atom with rearrangement to ainnamyl chloride, which has values of

0.58 and 0.68 at 30.0° for ethanol and aqueous dioxan respectively and 0.15 in WN-dimethylformamide, Waight and Weinstock concluded 22.

that the ion-pair is more likely to lose configuration in strongly ionizing media, such as ethanol ar aqueous dioxan than in N.N-dimethylformamide. Weinstock found that chloride ions effect with the LiC1 concentration bothki andkraol thevariationak.1 being linear, and its effect somewhat greater than that of sodium perchlorate. He found that the rate of racemization k in N N- rac dimethylformamide with added LiC1 increases linearly and very steeply with salt concentration up to 0.055 M., at higher concentrations of LiC1 the rate increase was less pronounced but remained linear with salt concentration as far as 0.25 M. 16 Weinstock has interpreted his results as follows:

1) IHC1;T:=7± 211+ Cl RC1 racemic k-1

2) Cl- + Cl- 3 racemic

k 3) IRC1 + Cl- RC1 racemic

Assuming that initially k..1 is greater than k2, the addition of chloride ion will provide a second path for the formation of racemic product from the ion-pair intermediate. At a salt concentration of about 0.055 M the rate of return to starting 23.

material is equal to the rate of inversion of configuration by paths 2) and 3).

i.e. k k2 +k3 cii

He concluded that the subsequent smaller increase in k ran. with salt concentration is due to an S N2 displacement with rate constant k4.

On this explanation he suggested that an asymmetric intermediate is formed: C4- ' Ph.CH - CH CHf

C-61

36 (vi) Exchange reactions with C1. Attempts were made by Weinstock to measure the rate of exchange of 1 -phenylallyl chloride with isotopically labelled chloride ions present in low concentration in order to get further information concerning the nature of intermediate leading to isomerization. He attempted to measure the specific activity of both isomers at the same time, but obtained no useful results due to experimental difficulties.

24:

B. Isomerization of 1-phenylallyl-Nitrobenzoate

The rearrangement of 1-phenylally1 p-nitrobenzoate (VI) to trans-cinnamyl p-nitrobenzoate (VII) was first investigated by Burton29 and by Meisenheimer and Schmidt30

- CH - CH = CH2 CH = CH -CH2 0 0 0`;C/ O

(VI) (VII)

NO 2 NO2 Burton examined the isomerization in different solvents and observed that the rearrangement occurred smoothly and completely, the rate of rearrangement increasing in the sequence: p-xylene ‹chlorobenzene cinnamyl acetate and cinnamyl p-nitrobenzoate was formed.

Mainly on the basis of this evidence Burton suggested that the anionotropic rearrangement of 1-phenylally1 p- nitrobenzoate proceeds by way of a rate-determining ionization 25•

into a carbonium ion and a fully dissociated anion, and that the mesomeric carbonium ion then rapidly undergoes further reaction.

0 - 9 = 0 cinnamyl millilli•••••••••04 VI (1 7- " H' c2+ p-nitro- benzoate E0 2 31 Further experiments carried out by Burton showed that when cinnamyl p-nitrobenzoate is heated with tetraethyl.. ammonium acetatate in acetic anhydride under the same conditions of time, temperature and concentration as those used for

1-phenylally1 p-nitrobenzoate no appreciable quantity of cinnamyl acetate was detected, he concluded that the substit- ution of p-nitrobenzoate ion by acetate ion occurs during and not after the isomerization. 30 Meisenheimer and his co-worker have shown that the isomerization of 1-phenylallyl p-nitrobenzoate is "autocatalytic" and is accompanied by the formation of p-nitrobenzoic acid.

They claimed that the addition of p-nitrobenzoic acid has a little effect on the rate of rearrangement in ether, although increasing it considerably in the absence of solvent.

Further support for Burton's suggestions has been 26.

32 adduced in a later paper by Catchpole and Hughes They showed that in methylcyanide and acet4nhydride as solvents, the rate is increased by lithium p-nitrobenzoate, but the increase is of a type which can be accounted for as an effect of ionic strength on the rate of ionization to the mesomeric carbon cation.

Braude, Turner and Waight33,34 re-investigated the isomerization of 1-phenylallyl p-nitrobenzoate in both aqueous and non-aqueous solvents, following the isomerization by the spectrokinetic technique, they found that the rate of rearrangement in chlorobenzene solution was greatly dependent on the method of purification of the ester and of the solvent, and that the reaction is accompanied by the formation of small amounts of p-nitrobenzoic acid, which they estimated titrimetrically or polarographically. They found that the rearrangement is greatly accelerated by p-nitrobenzoic acid, the rate of isomerization increasing linearly with acid concentration. These workers studied 14 the reaction in the presence of C-carboxyl p-nitrobenzoic acid as a source of p-nitrobenzoate ions, the fate of the labelled p-nitrobenzoic group being determined by separating the acid and the two esters at various stages and measuring

27.

their specific radioactivity in N - N-dimethylformamide solution. They found that at low concentration the rate of exchange is much less than the rate of rearrangement, and concluded that the uncatalysed "spontaneous" rearrangement is intrd—molecular. .•••••••

Ph.Ch - CH = CH Ph.CH 2 CH2 0 .0 . cinnamyl 444..,L. p-nitro- benzoate

2 NO2

At higher concentrations of p-nitrobenzoic acid the total rate of exchange increases rapidly. The larger part of the exchange reaction takes place without rearrangement and must be due to bimolecular substitution by p-nitrobenzoic acid or p-nitrobenzoate ion at the y-carbon atom. They suggested for the acid catalysis direct attack of undissociated acid molecules at y-carbon atom of the ester through a cyclic transition state involving a hydrogen bridge:

28.

Pr

Ph. CH - CH = CH2 HO - C = 0 0 c

II 0 * NO2

NO2

...7;;; CH .. Ph.CH = CH - CH Ph. CH CH2 2 C 0 "

NO2 HO NO 2 2

They also attempted to discover the effect of added anions in the presence of large amounts of free acid, which may have been present in Burton's experiment with NEtkOCOCH3.

The rearrangement was carried out in chlorobenzene in the presence of diisopentylammonium bromide. As no cinnamyl bromide was detected in the products, the sole effect of the salt being to increase the amount of p-nitrobenzoic acid formed and thus the rate of rearrangement, they concluded that under these conditions the rearrangement essentially intramolecula r.

Pocker35 studied the thermal isomerization of 1- to 3- phenylallyl p-nitrobenzoate in chlorobenzene at 29.

155.5°, and found that during the isomerization minute

quantities, smaller than those reported by Braude, Turner and Waight, of p-nitrobenzoic acid are produced. He reported that the isomerization in/Presence of p-nitro-

benzoic acid is subject to only a mild catalysis by added

p-nitrobenzoic acid, and that the presence of pyridine and

tetra-n-butylammonium p-nitrobenzoate has no effect on the rate, although at the high temperature used, considerable decomposition of the latter occurs to produce trin-butylamine and butyl p-nitrobenzoate. He concluded that the isomeri- zation in the absence of any added acid is purely a unimolecular process. 36 Pocker attempted to distinguish if the unimolecular

process is intermolecular or intramolecular, with the help 18 of 0. He found that when 1-phenylallyl benzoate is 18 heated in the presence of 0-benzoic acid in chlorobenzene at 155.5, the acid recovered at various intervals shows 18 a steady diminishing of its 0, and the amount of the acid was shown to be constant. He reported that the conjugated isomer can undergo only a negligible amount of isotopic exchange after formation. He also carried out the Aithe 18 rearrangement in presence of tetra n-butylammonium 0 30.

benzoate. Pocker interpreted his results in terms of an ionic mechanism (S 1)modified in a solvent of low ionizing N power , to contain a rate determining ionization to phenylallyl carbonium benzoate ion-pairs.

Turner and Braude37'38 showed that the isomerization of 1-phenylallyl p-nitrobenzoate was intramolecular by the 18 use of 0-carbonyl labelled ester. They found that the carbonyl and alkoxy oxygen did not become equivalent, indicating that the fragments of the rearranging molecule remain in close association and proposed a six-membered ring intermediate. By the use of p-nitro (carboxy 14C j benzoic acid the bimolecular reaction was shown to involve attack by essentially undissociated acid molecules at both positions 1- and 3- in the ester, as well as catalysis of the intramolecular reaction.

CH, Ph.CH - CH = CH Ph.CH CH Ph.CH - CH = CH2 2 • • 2 0 0 6 0 14i80 C =Z:.

-1""- NO NO 2 NO2 . 2 31.

III The Effedt Of SUbStitnentis 0, the, 1:eacq.vity

of the Side Chain in tote Benzine ring

In compounds of type (VIII), the reactivity of the side chain (1) is effected by the substituent (R).

(VIII)

The most general relationship known for the effect of the substituent on the rates or equilibria4 is the

Hammett linear-free-energy relationship39'4°.

log k/ko = p 6'

are rates or equilibrium constants for where k and ko reaction of the substituted and unsubstituted compound, p is the reaction constant dependent upon the nature of the reaction, being a measure of the susceptibility of a given reaction series to polar substituents, d is a substituent constant independent of the nature of the reactions 6) is a quantitative measure of the polar effect in any reaction of a given meta- or para- substituent retatt,..m twa hydrogen atom, i.e. it depends on the nature and position of the substituent (R). 3 2 v

Hammett selected as the standard reaction for obtaining this constant the ionization of substituted benzoic acids in water at 25.00

K R-C6H4COOH i„, lo g K c6H5c00H

Values of I obtained in this way are referred to as primary ie -values. Values of 6) obtained from some other reaction employing a value determined for the reaction constant p, i.e. = (l/p) log k/k0 , are known as secondary 6> -values. A positive e value for a substituent indicates that it is a stronger electron attractor than hydrogen, substituents with negative values are weaker electron attractors than hydrogen.

To obtain p for a given reaction series it is necessary to measure rates or equilibrium constants for a number of compounds, each having the reaction centre under consideration and each having a different ring substituent with a known e value. The experimental values of log k or log k/k0 are plotted against the corresponding values of ••G' and the determination of the slope of the best line through the points (unless a non-linear relation- ship results) gives the value of p. 33.

The Hammett equation in its simple form is

generally not applicable to the reaction of ortho- substituted benzene derivatives. Here the substituent lies close to the reaction site and may influence the reaction by its electron-attracting ability and steric bulk 41 interaction. Jaffe has collected about 42,000 rates and equilibrium constants for 3180 reactions and shown that the

Hammett equation is followed with a median precision of

- 15%

The sign and the magnitude of the reaction constant

p have been used as an important tool in the study of reaction mechanisms. Since the ionization of benzoic acids in water, for which p is equal by definition to

+ 1, is facilitated by electron-withdrawing substituents, it would appear that a positive value of p indicates a reaction in which a negative charge (or partial negative charge) is developed on the side chain. Similarly, a negative value of p should correspond to the development of a partial positive charge on the side chain. The magnitude of p should therefore be a measure of the magnitude of the developing charge and of the extent to which it is able to interact with the substituents. This 34.

interpretation is at least qualitatively correct when

p is far from zero. But it is doubtful when p is close to zero because the sign of p can then be converted by

moderate change of temperature. 42 Hammett has indicated that the following general consideration applies to any reaction which can be formulated as follows:

A + BC AB + C

If A contains a meta- or para- substituted

benzene ring and is electron-rich relative to B (i.e. nucleophilic displacement is involved), electron attracting meta- or para- substituents will hinder the formation of the new A - B bond, and thus a negative p value is implied. Similarly electron attracting substituents in the A component in an electrophilic displacement (i.e.

A is electroppoor relative to B) will stabilize the resulting A - B bond so that p will have positive value if the reaction of this type. In a similar fashion the type of displacement reactions leading to positive and negative values of p can be predicted for the substituents in the C component. When substituents are in the B 35.

component, the formation of the new A - B bond and the

breaking of the old B- C bond are effected in opposite

directions by electron release. Thus for example in a

nucleophilic displacement on B the former is retarded and the latter facilitated. The sign of p in these reactions under given conditions tells whether nucleophilic

(+ p) or electrophilic (- p) participation provides the greater driving force.

Modification of pe Relationship:

The large deviations which are found with resonance 42 43 4445 electron donating substituents ' ' '46 when the reaction centre is capable of a strong electron withdrawal, are due to direct resonance interaction between the substituent group and the reaction centre and have led to the suggestion of alternative sets of 6 constants. One group of substituent constants, originally 41 42 for use in reactions of aniline and phenol derivatives ' 48 and called e - (sigma minus) values , applies to para- substituents capable of mesomeric electron withdrawal, and gives more closely linear plots than d for aromatic nucleophilic substitution reactions of phenol, phenolic esters, aniline dimethylaniline and anilides. 36.

On the other hand 64+ (sigma plus) values apply

to para substituents capable of mesomeric electron donation.4849 '

values are defined from the solvolysis of substituted

2-phenyl-2-propyl chlorides in 90% aqueous, acetone at 0 47'49. 25 In order to make the bI.4. and 6r- scales as

nearly as possible alike, a normalizing procedure was used.

Since resonance effects are much less important for certain

meta-substituents, the plot of log k/k0 versus the Hammett I -values for these substituents in the standard reaction is nearly linear, and its average slope

is adopted as the value of po. The - values

are then obtained:

log le.R /k standard reRction 6 .1- R Po

so the new equation can be used as follows:

log k/ko = p +

This is very nearly the same as the Hammett equation itself and the symbols hve similar significance, the notation e indicating that the attacking reagent is cationic. This equation has been used in aromatic side chain 37•

reactions in which positive charge capable of direct

resonance interaction with the ring is generated. The relative rates of electrophilic side chain reactions

which deviate from the standard Hammett equation, correlate 47 well with G" values

Van Bekkum et a115 calculated p constants for a number of reactions, using only substituents for which extra resonance seemed to be impossible. From the p

constants obtained, a constant known as d ° (sigma norma157). Several reactions are much better correlated by means of

6) 52 d ° than by mean of Yrkawa and Tsuno5354' used. an equation of the

form:

log k/ko = '+R - J) since d - 6 for a well behaved meta-substituent. is zero, these may be used to evaluate p. R is the slope of the plot of (1/p log k/ko - 6 ) versus

A specific example for use of this relationship is the rearrangement of phenylpropenyl carbinols55 in which large deviations are found when log k/ko is plotted

versus The deviation decreased when log k/k was e . o 38.

plotted versus 61 and disappeared in plotting log k/k o versus 6' + R I e - 61J (R in this case is 0.396).

It should be noticed that the Hammett correlation and the substituent effect on the inactivity of the side 41 chain has been discussed by Jaffe , Van Bekumm et al50, 56 Pal/m , Taft57,58, Murrell and Norman59, Stock and Brown6o, a Leffler and Grunwald and Wiberg62 39.

RESULTS

MID

DISCUSSION I. Solvolysis of Substituted Cinnnmyl Chlorides A. Results.

It has long been known that the solvolytic reactions of cinnamyl chloride can give rise to a mixture of 1- and 3- phenylallyl products. The mechanisms of the reactions were discussed

by Vernon and re-examined by Valkanas, Weight and Weinstock who determined the rate constants and the product composition of the reaction.

In order to investigate the effect of a substituent in the phenyl ring on the reaction mechanism, i.e. on the rate and on the produot composition, a series of substituted cinnamyl chlorides were prepared and the solvolytic reactions were carried out in a series of mixtures of aqueous dioxan and of ethanol-cyclohexane. This showed that all the substituted cinnamyl chlorides lead to a mixture of conjugated and unconjugated solvol,pic products in both aqueous dioxan and in ethanol cyclohexane. The reactions follow the scheme Shown below:

X - C6H4.CH su CH - CH2C1

-...... s1H.csA, 4,0 X - ,CH - CH vs CH X - C6H4.CH = CH - CH2C6 64 2 OB 41.

where the sabstituent X . p Br, p - Cl, p - F , p - CH3 and p CH30.

Table (I) shows the rate of hydrolysis and the composition of products in a series of mixtures of aqueous dioxan. The rates of the reactions are very sensitive to the amount of water present in the medium and correlate guiles well with the

ionizing power of the medium as measured by its Y-value63' 64 (fig. I). Grunwald and Winstein have defined the ionizing power,

Y, of a solvent as the logarithm of the rate of solvolysis of tert-butyl chloride therein relative to the rate of solvolysis in

80A aqueous ethanol, and have measured Y values for a large number of solvent mixtures. They found that the logarithms of the solvolysis rates of many compounds gave linear correlation in

Y expressed by the equation:

log K o mY + log lc...)

where k o is the rate of solvolysis in the standard solvent, chosen as 8C aqueous ethanol. The slope m measured the susceptibility of the substrate to the ionizing power of the solvent relative to tert-butyl chloride. Usually m has a value of about 0.4 for reactions which definitely belong in the bimolecular category, and a value of about 0.9 - 1.0 for reactions which are definitely 42.

unimolecular. Border-line reactions have intermediate values.

It can be seen from table (I) that the product ratio (r), i.e. the proportion of the unconjugated product to the conjugated product in each chloride increases as the proportion of water

increases. Generally when the substituent is electron-releasing

it causes an increase in the rate and in r, while if electron attracting it causes decrease in the rate and in r, under the same conditions.

From tablefII)and fig. (II) it can be seen that the rate of hydrolysis of substituted cinnamyl chlorides in 50A aqueous dioxan do not obey the usual Hammett treatment but, all the rate constants give an excellent linear relationship with cy+ values.

A collection of p-values for the pa+ correlation is given by 61 Okamoto and Brown47. Leffler and Grunwald pointed out that the p-values are always negative and are often large. In agreement with the expectation that these reactions are facilitated by electron donating substituent, the p-value for the hydrolysis of cinnamyl chloride is - 4.58. Table(III)shows the results obtained for the ethanolysis of cinnamyl chlorides in 96A ethanol-cyclohexane. As in the hydrolysis an electron-releasing substituent causes an increase in the rate and in r. From fig. (III) it can be seen that no correlation is obtained with the a -values, but that the data reveal an excellent correlation with a+ constants, the p-value for the ethanolysis of cinnamyl chlorides being - 5. 43.

TABLE I.

Solvolysis of Substituted Cinnamyl Chlorides in AcluousDioxan. The Effect of Ionizing Power Temp., 30.0°C

Svbstituent Dioxane k Product ( x- ) (min-1) Composition (% V/V) (r)

p - Br 50 0.0062 0.883 40 0.0310 1.000 30 0.1500 1.092

p - Cl 50 0.0086 0.840 40 0.0440 0,924 30 0.2150 1.082

p - F 60 0.0102 1.076 50 0.0570 1.230 40 0.3100 1.352

60 0.00572 1.070 50 0.03160 1.184 40 0.16500 1.292

60 0.0108 1.000 50 0.0610 1.218 40 0.3010 1.430

(Conte"...)

44.

Table I (Contd/...)

70 0.0185 1.243 60 0.1320 1.307 50 0.7800 1.423

p CH 0 90 1.560 3 0.0054 85 0.0360 1.641 80 0.2300 1.711

- results due to Weinstock

Values of log kT, plotted against Y give straight lines with slopes m of 1.25, 1.27, 1.20, 1.20, 1.22 and 1.47 were X c= p - Br, p - Cl, p - F, H, m - CH p - CH 3' 3 and p CH 0, respectively. 3 2.4 —

0.4 —

Fig. I

Rates of solvolysis of cinnamyl chlorides in aqueous dioxan as a function of Y. 46.

TABLE II

Substituent kt log k/k o a Q ( x- ) (min 1)

p - Br 0.0062 - 0.706 + 0.232 + 0,150 p - 01 0.0086 - 0,565 + 0.227 + 0,114 P - F 0.0570 + 0.255 + 0.062 - 0,073 H 0,0316 0,000 0.000 0.000 m - CH 3 0.0610 + 0,286 - 0.069 - 0,066 p - CH 3 0.7800 + 1,300 - 0.170 - 0.311 mp - mi0 141.200 3 + 3.655 - 0.268 - 0.788

- by extrapolation. Logik/ko 4.0

The relative rates of hydrolysis of cinnamyl chlorides in 5c aqueous

dioxan at 30.0.0 versus a ( 0 ) and a+ ( 0 ). 48. TABLE III. Solvolysis of Substituted Cinnamyl Chlorides in 96% Ethanol-

Cyclohexane

Substituent Temp. kt Product ( X- ) (oc) (min-1) Composition (r)

p - Br 60 0.000729 0.715 65 0,00129.0 70 0.002280

p - Cl 60 0.00107 0.662 65 0.00161 7o 0.00271

P - F 50 0.00158 1.283 6o 0.00390 7o 0.01040

Iii 50 0.00104 1.060 6o 0.00285 7o 0.00892'

m - CH 5o 0.00250 1.480 3 6o 0.007.80 . 7o 0.01830

p - CE3 3o 0,00199 1.800

40 0.00640 50 0,01950

p - cly 25 0.385 2.97 3o 0.580 25+ 0.500 1.71 25- 0,800 2.78

a results due to Weinstock. - f the presence of 0,1 M Na0Et.. - in the presence of 0.1 M NaC10 4 Log kik o- O p - 4.0 CH3°

3.0

2.0

1.0

0.1 0.2

a or a

Fig III

The relative rates of ethanolysis of cinnamyl chlorides in 960 ethanol-

cyclohexane versus a (0 ) and a+ ( 0 ) 50.

Salt Effects.

The hydrolyses of p-bromo- and m-methyl- cinnamyl chlorides were carried out in the presence of lithium salts.

Table IV shows the effect of added lithium salts. In general the rate increases in the presence of perchlorate ions, i.e., the rate increases with increasing - ionizing power of the medium. Bromide ions cause an increase in the rate identical with that caused by perchlorate, while chloride ions act in the opposite manner, i.e. they retard the hydrolysis due to the mass-law effect. The proportion of substituted cinnamyl alcohol obtained from each chloride decreases in the presence of salts. 5'-

TABLE IV

Solvolysis of p-Bromo- and m-Methyl- Cinnamyl Chloride in Aqueous Dioxan. The Effect of Lithium Salts. Temperature, 30.0°C

Substituent Dioxan Kind of Salt conc. kt r ( X-) (% V/V) salt (m/1) min-1

p - Br 40 0.000 0.000 0.0310 1.000 LiC1 0.1 0.0290 0.980 LiC1 0.5 0.0285 0.961 LiBr 0.1 0.0480 0.983

LiC104 0.1 0..0420 0.971 LiC104 0.5 0.0595 0.950

m - CH3 50 o.000 0.000 o.o6lo 1.218 LiC1 0.1 0.0595 1.156 LiC1 0.5 0.0435 1.100 LiBr 0.1 0.0904 1.153 LiC104 0.1 0.0740 1.10 LiC104 0.5 0.14401 1.00 5 2 .

The effect of Added Fluoride Ions

The fluoride ion is usually supposed to be more powerful nucleophile than chloride ion. Ingold and his associates studied the reaction of m-chlarobenzhydryl chloride with fluoride ion, supplied in the form of tetraethylammonium fluoride, in sulphur dioxide. They observed that the exchange proceeds to an equilibrium

R Cl R F Cl."

It seems probable that 1-phenylallyl fluoride should be less susceptible to isomeric rearrangement than the corresponding chloride in view of the known disinclination of aliphatic fluoride to undergo S N 1 type displacements. Thus it was thought that in carrying out the solvolysis of 1-phenylallyl chloride it might be possible to trap the intermediate by the addition of fluoride ion.

In the case of cinnamyl chloride there was the additional possibility that cinnamyl fluoride might be formed by an S N 2 displacement.

The solvolysis of cinnamyl chloride in aqueous dioxan and in ethanol cyclohexane was carried out in the presence of tetra- ethylammonium fluoride. The solvolysis product was separated after various times and its infra-red spectrum obtained. This showed no band attributable to the C-F stretching vibration, i.e. the spectra were identical with those for the solvolysis products in the absence of fluoride. 53.

The Effect of Added Base. 67 Catchpole and Hughes pointed out that's an S 2 mechanim N in solvolysis can only be excluded when it can be shown that the compound substituted is insensitive to substituting agents which are more strongly basic than the solvent molecule. Vernon1 has shown that in 50/0 aqueous ethanol the addition of sodium hydroxide in 0.015 M concentration increased the rate of hydrolysis of cinnamyl chloride by about 10%, an amount that he considered negligible. 18 Weinstock carried out the hydrolysis of cinnamyl chloride in 50 aqueous dioxan in the presence of varying concentrations of sodium hydroxide. He found that sodium hydroxide decreases the rate of hydrolysis just as it does for tert-butyl nitrate, 6 berthydryl bromide and other aubstances thought to undergo solvolysis by unimolecular mechanism, an effeot considered due to attack by hydroxide ions on protons of the solvation shell required for ionization of the organic halide. Weinstock observed that product ratio is dependent on the concentration of sodium hydroxide, the variation being consistent with the idea that some cinnamyl alcohol is formed as a result of bimolecular reaction involving hydroxide ions and occurring after the rate-determining step but before delocalization of charge in the mesomeric carbonium ion intermediate. 54.

Table( V)shamsthe results obtained by carrying out the solvolysis of some substituted cinnamyl chlorides in aqueous dioxan which are in quite good agreement with

Weinstock's observations. 5 5 .

TABLE V. Solvolysis of Substituted Cinnsmyl Chlorides in Aqueous Dioxan

- The Effect of Sodium Hydroxide. Temp., 30.0°C.

Sub st ituent D ioxan NaOH Kt Product ( X- ) (% vv.) (nvi) (min ) Composition

p - Br 30 0.000' 0.150 1.092 0.162 0.140 1.000 0.271 0,130 0.97a 0.481 0.110 0.950

p - Cl 40 0.000 0.0440 0.924 0.120 0.0400 0.883 0.481 0.0330 0.802

p - F 50 0.000 0.0570 1.230 0,240 0.0480 1.103 0.480 0.0230 0.931 • m - Cli 3 50 0.000 0.0610 1.218 0.233 0.0470 0.991 0.467 0.0305 0.901 56.

The liffect of Ag+

It is known that silver salts can function as catalysts, electrophilic in character, for nucleophilic substitution.

As a result of kinetic investigations the solvolpic reactions of alkyl halides with silver ion64'70'71 have been pictured as

S 1 - like substitutions, initiated by the ionization of the N halogen compound on the surface of the silver salt with the aid of adsorbed silver ions, and completed through the uptake by the formed carbonium ion of an ion from the solution

Ag X R+ + AgC1 R Cl surface

R+ + SOH ROS + H+

72 Further support has been given by Ingold for this interpretation, namely:

i) The effect of constitutional changes on reaction rate is qualitatively similar for silver-ion catalysed substitution and for unimolecular substitution. Thus for both reactions the alkyl rate series, tertiary ) secondary ) primary is observed.

ii) The stereochemical course of silver ion catalysed substitution has been shown70P71 to follow the rules applicable to S 1 substitutions and not the different rules of S 2 N N substitution. 1

iii) Where the S N 1 substitution leads (through isomerization of R ) to rearranged products, while S N 2 substitution gives normal products, the silver-ion reaction has been shown to yield rearranged products73,74 Cinnamyl chloride, bromide and iodide on treatment with ethanolic potassium hydroxide give exclusive cinnamyl ethyl ether. When the ethanolysis was performed in the presence of silver oxide, a considerable part,alout 25-40%, of the product was found to be 1-phenylallyl ethyl ether.

Table VI shows the results for the ethanolysis of cinnamyl ohloride in the presence of Ag+. It can be seen that the silver ion causes an increase in the rate and a decrease in the product ratio (1), i.e. the proportion of rearranged product is increased.

At higher concentration of silver nitrate the reaction is complicated, and first order rate constant obtained increases with the time, and the end value is irreproducible. This may be due to the formation of alkyl nitrate. 56.

TABLE VI.

Ethanolysis of Cinnamyl Chloride in 96% Ethanol-Cyclohexane. The Effect of ARN03 Chloride Conc. 3,5 x 10 5 Temp. 50.0°C.

--- Salt Conc. kt. Product (m/1) (min-1) Composition (r')

0.000 0.00104 1.060 3.75 x 10-5 0.00271 0.759 5.62 x 10-5 0,00275 0.750 15.00 x 10-5 0.00321 0,735 22.50 x 10-5 0.00432 0,725 0.1 - Ag20- 0.00870 0.630

r OS.)/iR OSJ 59.

B- Discussion

As previously indicated (page 7 ) Vernon concluded that the solvolytic reaction of cinnamyl in 50% aqueous ethanol occurs by the unimoleculr mechanism and that in pure ethanol there is a bimolecular component. 17 Valkanas claimed that the solvolysis of cinnamyl halides do not follow the S 1 mechanism involving the N mesomeric phenylallyl carbonium ion. He considered that the solvolysis of cinnamyl chloride, both in 60% aqueous dioxan and in pure ethanol could be represented by a single mechanism. He suggested that the hydroxylic solvents weaken the C-Cl bond by hydrogen bonding on highly activated molecules forming the ion-pair (I), the resulting polarisation of 1- and 3- carbon atoms afterwards allows the formation of the four-membered ring (II) which by abnormal internal ion return can give 1-phenylallyl chloride.

The suggested scheme was: 6o.

Ph.CH = CH - CH2OS 1 SOH

6+ 6- Ph.CH = CH - CH2 Cl Ph.CH -2 CH CHr.C1 • • • HOSE ( I )

.' CH RIC1 .';// SOH Ph.CH :CH2 ROS + R' OS .• .'s ci RC1 ROS

The species (II) being intermediate between the highly stable R'Cl and rather unstable RC1, will preferably give normal ion return with the formation of RIC1 but some abnormal ion return may be possible and if this occurs a rapid solvolysis to ROS products is inevitable. The rate controlling step must be the formation of the ion-pair (I), which is also reactive giving RIOS solvolysis products. 61.

Valkanas reported that salts exert a large effect on solvolysis reactions of the cinnamyl halides, he considered that the acceleration in the solvolysis rate was too great

to be accounted for by an ionic-strength of the medium and concluded that the catalytic effect is strictly bimolecular, i.e. the salt catalysis in the solvolysis reactions of cinnamyl halides involves the formation of a six-mtombered ring intermediate involving a molecule of salt and leading to 1-phenyl allyl chloride.

Ph.CH = CH - CH2C1 + M Yd--Ph.CH CH -.L CH2 6 • „„. Cl... M Y SOH

Ph.CH = CH - CH2OS SOH . CH. *7 '%`% CH Ph.CH 4 2 Cl

SOH

SOH - CH = CH Ph.CH - CH = CH 2 2 OS Cl

Valkanas reported that sodium perchlorate increases the rate and this he explained as being due to the setting up of a. rapid equilibrium with the formation of cinnamyl perchlorate. 62.

Because of the insolubility in ethanol of sodium chloride the equilibrium is disturbed and more cinnamyl perchlorate is formed.

When the exchange takes place with cinnamyl halide and a salt another step is involved. The ion exchange reaction takes place before the formation of the ion-pair, when the cinnamyl halides are only slightly polarized or exist as an excited molecule.

Ph.CH = CH - CH2 X `Ph. CH = CH - CH2 "M+ MY

Ph.CH = CH - CH2 Y

The more nucleophilic the anion the more likely is ion exchange to take place in this way. Valkanas found that 36 - with C1 and cinnamyl chloride, equilibrium was obtained instantaneously and that in the presence of the more highly nucleophilic azideion an instantaneous complete conversion to cinnamyl azide took place. 18 Weinstock re-examined the solvolysis of cinnamyl chloride. His results are in quite good agreement with the 63.

general conclusions of Vernnn, i.e. that the solvolysis is

entirely unimolecular in highly ionizing aqueous media but

that there is evidence of a bimolecular component in the less

highly ionizing absolute ethanol. Weinstock made use of the

solvolysis product ratio in the various mixtures taking account

of the effects of added nucleophiles on this ratio and on the

rate of the reaction. He supported the idea of nucleophilic

assistance by the anion in the formation of the ion-pair

intermediate to account for the effect of azide, bromide and

ethoxide ions; the rate increases by perchlorate he explained

as due to an increase in the ionic strength of the medium

while the rate decrease by chloride ion resulted from a mass-

law effect. Weinstock suggested the following scheme for

the salt effect on the hydrolysis of cinnamyl chloride:

slow Ph. CH = CH - CH Cl CH = CH - CH2 2 fast (I) Cl fast H2O:

fast Ph. CH " i CH CH Ph.CH = CH - CH 2 H 0 2OH +. HCl (II) Cl- 2 H20 [fast

Ph. CH(OH) CH = CH 2 + HC1

Hydroxide ions in high concentration can react with intermediate (I) at the 3- position before complete delocalization 64.

of charge so as to increase the proportion of unrearranged alcohol. He found that neither chloride nor bromides ions in 0.1 M concentration have a detectable effect on the product ratio, i.e. the common-ion rate depression is not accompanied by an increase in the proportion of 1-phenylallyl alcohol; 1-phenylallyl chloride is not formed so that either return from an intermediate, such as the mesomeric carbonium ion-pair, which can give secondary chloride, is negligible or anions have a much greater differential reactivity with the 3-position of such an intermediate than have neutral molecules. The former seems unlikely and some molecular orbital calculation on thaphenylallyl carbonium ion by 5 Professor Jackman and Dr. Hardiion support the letter view.

The results obtained in the present work for the hydrolysis of substituted cinnamyl chlorides show that, as with cinnamyl chloride, the solvolysis occurs by the unimolecular mechanism.

Evidence that the solvolysis is unimolecular in aqueous dioxan can be derived from the correlation of the rate constants with the ionizing power, as measured by

Grunwald and Winstein's Y-values. In fig. I log kt is plotted against Y, the slopes, m, of the lines are typical for unimolecular reactions, and they are in quite good 65.

agreement with the values obtained by Weinstock. Similarly the addition of hydroxide ions decreases the rate of hydrolysis as in the case of cinnamyl chloride itself.

In the hydrolysis of p-bromo- and m-methyl- cinnamyl chloride the rate increase by strongly nucleophilic bromides ions is of a magnitude typical of an ionic strength effect. The effect of lithium chloride is typical of the mass-law retardation of unimolecular solvolysis by common ion.

On the basis of the simple unimolecular mechanism, one would not expect to find any variation in the product ratio for each chloride under differing conditions of solvent composition. The product ratio data reject this possibility.

It is suggested that two intermediates are involved for the solvolysis of substituted cinnamyl chlorides, the first which is formed in the rate determining step, gives only the corresponding cinnamyl products and also gives rise to a second intermediate from which both allylic isomers are obtained. It should be noticed that the behaviour of these intermediates changes with respect to the substituent in the phenyl ring.

The suggested scheme is as follows:

66.

slow

X - C6H46CH m CH CH Cl Ato.••••.••••• X 0 H CH m CH - CH 2 6 4' 2 (I) Cl fast fast H2O

fast. X - C6H'H4 4(;CH CH CH X - c H .CH m CH - CH OH • 2 H2 0 6 4 2 HCl

H2O fast

X - C6H4. CH - CH = CH2 4. HC1 OH

When the substituent is electron-attracting the first intermediate is more likely to react with water to give cinnamyl products, than to undergo further dissociation to give the second intermediate which can give rise to both allylic alcohols probably with more of the cinnamyl alcohol, i.e, the charge on the 1-carbon atom is less than on the 3-carbon atom. An electron attracting group at the

1-position of an allylic carbonium ion causes a decrease in the positive charge on the 1-position and increases the charge at the 3- position. When the substituent is electron-donating, the first intermediate (I) is more likely to give the second intermediate (II) than to give the corresponding cinnamyl products. The positive charge is greater at 1-carbon atom than 3-carbon atom, and in fact the positivity of the 1-carbon atom is directly proportional to the 67.

76,76a electron-donating ability of the group. Pilar carried out some

molecular orbital calculations on the polarizabilities of allyl cations

which show that an electron donating group such as an alkyl group

causes• a decrease in the electron density at the 1-position and an

increase in the electron density at the 3-carbon atom, which is in

q uite good agreement with the above explanation. Therefore

electron-attracting substituents give rise to more of the substituted

cinnamyl products, while electron-donating groups give rise to more

of the substituted 1-phenylally1 products.

The product ratio (r) for each chloride increases with

increasing ionizing power of the solvent, in solvents containing

more dioxan, the ionizing power is less, and some reaction of the

ion-pair (1) with water can take place at a stage where the departing

chloride ion is still closer to the 3-carbon atom than to the

1-carbon atom, the positive charge being effectively localized at the

3-carbon atom. In solvents containing less dioxan the ionizing power

is greater and the positive charge is more effectively delocalized

than in the farmer case. The product of the reaction of the ion-

pair is the cinnamyl compound so that the proportion of this compound

in the final mixture of products is higher in the former case than

in the latter.

The rates of the overall reaction do not obey the usual

Hammett equation presumably because of retioname interaction of the 68.

para-substituent with the electron-deficient centre of the transition state. The failure of the Hammett equation for the correlation of side chain reactions involving large electron deficiencies in the transition state was pointed out by Swain and Langsdorf43, further results of Okamoto and Brown47 have confirmed the deviation of other electrophilic side-chain reactions from the Hammett equation. As mentioned previously (page 35) those deviations disappeared when relative rates are correlated with a+ values. In carbonium ion reactions, the delocalization of charge is important and the simple a-values do not serve at all for correlation. The blend of inductive and conjugative effects in the a+ values is one that provides a satisfactory correlation for many carbonium ion reactions of benzenoid compounds.

The deviation of hydrolysis rates of substituted cinnamyl chloride in 5C aqueous dioxan from the Hammett equation, and the fact + that the data reveal an excellent correlation with the a constants is in quite good agreement with the above explanation. Groups such as p-methyl and p-methoxy, Which can help distribute the positive charge, exert this effect on the transition state and cause an increased solvolysis rate, In the para-position a methoxyl group invariably produces a rather large rate enhancement, undoubtedly because of the oxygen atom can accept a considerable fraction of the positive charge via resonance structure. 69.

From the physical and chemical properties of the ground 77 states of halogenated molecules it has been concluded that the halogens have -I (electron-attracting) and +M (electron-donating) effects, and in the halogen series these effects are greatest for fluorine and least for iodine. Spectroscopic evidence gives the reverse order for the donating (+M) effect and the opposite sign (+I) for the inductive effect. Usually the halogens act as deacti- vating groups, i.e. the (-I) effect operates against the (+M) effect the reactivities at the para positions of fluoro, chloro and bromo- benzene are not well fitted by the Hammett equation78. The fluoro substituent sometimes acts as an activating group as shown from its negative cr+ value47'59 '50' In the hydrolysis of substituted cinnamyl chlorides +M effects operate against the -I effects, i.e., the p-fluoro substituent behaves as a less strongly electron- attracting group in these cas es than in reactions where the resonance- interaction does not occur.

The ethanolysis of substituted cinnamyl chlorides requires nucleophilic assistance by solvent in the rate-determining step, as 19 suggested by Valkanas, Weight and Weinstock for the ethanolysis of cinnamyl chloride, based on the suggestion of Streitwieser10 for the solvolysis of but-t-enyl chloride. Alternatively, the facts may be explained by unimolecular cM bimolecular concurrent mechanisms798o'

The deactivated chlorides require more nucleophilic assistance by 70.

solvent in the rate detmining step than the activated chlorides.

Or in the case of the dual mechanism the unimolecular route is predominant in the activated chlorides, while the bimolecular route is predominant in the deactivated chlorides. The suggested scheme is as follows: HOEt slow (54 i X "' C6H4. CH = CH - CH Cl ------1 X - C H CH = CH - CH 2 v------4' 6 4. •a I fast -61 fast EtOH HOEt .• • If X - C H .CH GE -11;;SA1 fast X - CH OH = CH - CH OEt 6 .. 2 4 2 4 - . • • • Et 0H (If) Cl EtOH fast +HO].

X - C6H4.CH(OEt) CH = CH2 + HCl

The first intermediate (or transition state) (I) gives only the corresponding cinnamyl ethyl ether, and predominates in the case of deactivated chlorides. The second intermediate (II) gives both isomeric ethers, probably in approximately equal amounts or with more of the cinnamyl product in the deactivated group and more of the l-phenylallyl product in the activated group of chlorides.

The variation of the product ratio (r) is in quite good agreement with the above suggestion.

As in the hydrolysis of the cinnamyl chlorides the relative 71.

rates of the ethanolysi s do not obey the usual Hammett equation, the data give an excellent correlation with the a+ values.

The p-fluoro substituent in this case also acts as an electron- attracting group. 72.

II - Solvolytic Reactions of 1-Phenylally1 Chlorides

A. Results.

It is known that the solvolytic reactions of 1- phenylallyl chloride in aqueous dioxan and in ethanol- cyclohexane yield two isomeric products and are accompanied by isomeric rearrangement. In agreement the reactions of substituted 1-phenylallyl chlorides yield two isomeric products and are accompanied by isomeric rearrangement, the reactions follow the scheme:

X - C6114. CH - CH = CH2

Cl

HOS

1 X - C H .CH = CH - CH2C1 6 4 X - c6H4.CH = CH - CH2OS

.CH - CH = CH 2 tS

(X = p - Br, p Cl, p - F and m - CB 3). 73.

The chlorides in which X = p - CH30. and p - CH3 cannot

be prepared due to their rapid isomerization to the cinnamyl

chlorides under the experimental conditions.

Table (VII) shows the mean values of the first order

overall rate constants and the composition of products for

substituted 1-phenylallyl chlorides in a series of mixtures

of aqueous dioxan. The rates of reaction are very sensitive

to the amount of water present in the medium and give good

correlation with the ionizing power as measured by Grunwald and

Winstein's Y values. In (fig.IV) log kt is plotted

against Y, the slopes (m) of the lines being, 0.835,

1.00, 1.02, 1.02 and 0.93, where the substituent (X)

is p - Br, p - Cl, p F, m - CH and H respectively. 3 In each chloride the fraction of conjugated chloride

increases as the concentration of water decreases, and the

relative amounts of 1-phenylallyl and cinnamyl alcohols

produced are slightly increased.

From the table it can be seen that the rates of

hydrolysis increase in the series p-Br /- p-C1 <1: H

'gym-CH p -F and the fraction of the 1-phenylallyl

chloride undergoing solvolysis decreases when the substituent

is an activating group, but increases when the substituent is a deactivating group. The relative rates of hydrolysis 74.

of substituted 1-phenylallyl chlorides in 85% aqueous

dioxan deviate from the simple Hammett correlation but give

better correlation with d + constants with slope (m) =-4.25

as shown from (fig. V)-

Table (VIII) shows the results for the ethanolysis

of substituted 1-phenylallyl chlorides. Generally the same

observations can be made as in the hydrolysis.

In p-F and m-methyl-l-phenylallyl chlorides log kt varies linearly with the mole fraction of the ethanol in the medium (see fig. va).

The relative rates of ethanolysis do not correlate with either e or c (fig. VI: ).

The p-F substituent in the hydrolysis and in the ethanolysis acts as an activating group. 7 5..

TABLE VII

Solvolysis and Isomerization of 1-Phenylallyl

Chlorides in Aqueous Dioxan. The Effect of Ionizing power. Temp., 30.0°C.

Substituent Dioxan Solvolysis kt X-ROH (X - ) (%V/V) ( % ) (min-1) ( % )

p-Br 85 43,6 0.0175 59.3 8o 49.2 0.0505 64.3 75 53.2 0.1350 70.5

p-Cl 85 44.1 0,0296 61.6 80 46.5 0.0625 60.9 '' 75 48.1 0.2100 61.5

p-F 90 37.5 0.0270 73.0 85 39.6 0.1230 76.8 8o 40.7 0.3750 78.0 x H 90 36.1 0,0097 66.6 85 41.5 0.0510 70.6 8o 43.4 0.1690 70.0

m-CH 32.7 3 90 0.0177 75.2 85 35.1 0.0815 75.9 8o 39.4 0.2730 79.1

18 - Results due to weinstock m = 0.93. Fig IV Rates of solvolysis of-, 1-phenylallyl chlorides in

aqueous dioxan as a function of Y.

•rn

2.0 1.6 0;8 0.4 • Log kik()

Fig V 0.2 0 1 0.1 0.2 0. a or a

The relative rates of hydrolysis of 1-phenylally1 0.2 chlorides in 85% aqueous dioxan at 50.0°c.versus a (0 ) and 0.4 • p - Cl a (

p - Br -4 -4• 77.a

TABLE VIII

Solvolysis and Isomerization of 1-Phenylallyl Chlorides in Ethanol-Cyclohexane. Temp. 30.00C.

Substituent Ethanol Solvolysis k X-ROEt t-1 (x -) (% V/V) ( % ) (min ) ( % )

p-Br 96 73.2 0.021 76.2 p-Cl 96 71.1 0.023 68.5 p-F 96 63.o 0.1350 83.7 90 62.0 0.0970 83.6 8o 62.1 0.0740 83.o 7o 61.o 0.0440 81.6 m-CH 96 58.o 0.1450 85.1 3 90 57.3 0.1146 84.2 8o 56.2 0.0705 83.6 70 55.7 0.0430 82.1

112E 96 69.8 0.0566 78.3 Log kiko

Fig VI

The relative rates of

ethanolysis of 1-phenylallyl chlorides

in 96/ ethanol cyclohexan

at 30.0°C versus a+ (0 ) and. a ( 0 ) 1.2

1.1

1.0

0.9

o.8 reN0

0

0.7

0.6

Fig. VII Rates of ethrmolysis of p-fluoro-l-phenylally1 chloride (0 ) and m-methyl- 1-phenylally1 chloride (0 ) in ethanol-cyclohexane as a function of the mole fraction of ethanol. Temp. 30.00C. 80.

Salt Effects

The solvolysis of m-methyl-l-phenylallyl chloride was

carried out in the presence of lithium salts, chosen because of

their high solubility in organic solvents. The results are

shown in table (a). It can be seen that the rate increases in

the presence of perchlorate ion, due to the effective increase in

the ionizing power of medium. Lithium chloride increases the rate

only slightly compared with the large increases in the presence

of perchlorate. The proportions of 1-phenylallyl products are very slightly affected by chloride or perchlorate ions, while the propotion of isomeric rearrangement is quite considerably increased in the presence of chloride ions and decreased in the

presence of perchlorate.

Table (X) gives the results of the solvolysis of 1-

phenylallyl c'lloride in ethanol-cyclohexane in presence of Ag+

and shows tha t the overall rate increases as the concentration of Ag+ is increased. The product ratio cannot be calculated very accurately because of the very low concentration of silver nitrate.

The solvolysis of 1-phenylallyl chloride in aqueous dioxan and in ethanol-oyclohexane in the presence of tetra,ethylammonium fluoride gives a product with an I.R. spectra containing no

C-F band. 81.

TABLE DC

Solvolysis of and Isomerization of 1-(m-methylphenyl)ally1

Chloride in Aqueous Dioxan and in Ethanol-cyclohexane. The Effect of added Lithium Salts. Temp., 30.0°C.

Diann Ethanol kind of conc. Solvolysis kt X-RCS 1) V/V V/V Salt (m/1) ( % ) (min OD

85 None 0.000 35.1 0.0817 75.9 85 LiC1 0.058 32.0 0.1030 75.1 85 LiC1 0.116 29.0 0.1290 75.0 85 LiC10 0.048 43.0 0.1300 75.1 4 85 LiC10 0.097 51.0 0.1480 74.0 4

96 None 0.000 58.0 0.145 85.1 96 LiC1 0.199 54.0 0.154 83.3 96 LiC1 0.588 53.2 0.159 82.1 96 LiC1 0,777 52.0 0.175 81.0 96 LiC10 0.132 56.2 0.230 83,3 4 96 L1C10 0.281 0.295 83.6 4 55.2 96 LiC10 0.510 83.o 4 55.4 0.485 96 NaOEt 0.500 - 0.1146 - TABLE X

Ethanolysis of 1-phenylallyl Chloride in 9 0 Ethanol- Cyclohexane in presence of AgNO3. The Effect of Ad/. Chloride Conc. 4 x 15.1. Temp., 30.00C.

Salt Conc. kt Solvolysis X-ROEt (mil) (min-1) ( % ) ( %

0,000 0.0566 69.8 78,3

4.5 x l05 0.1100 72.o 49.9 7.5 x 10-5 0.1350 15.5 x 10-5 0.2400 0.1 - Ag20 - 0.083

83.

Ionization of Substituted Cinnamyl Alcohols in 100% Sulphuric Acid

Since sulphuric acid of excellent quality is available in

concentrations both above and below that corresponding to 102%

(absolute) sulphuric acid, the preparation of the latter may be

accomplished readily81 Essentially, the method of preparation

con/Ants of mixing concentrated and fuming sulphuric acids in the

appropriate proportions. A freezing point of approximately 10.5°C

for the mixture indicates that a composition corresponding to the

100% acid has been attained.

Practically all organic compounds, with some exceptions, 81 are soluble in absolute sulphuric acid. Kendal and Carpenter

have investigated the solubility of a wide variety of oxygen-

containing compounds by the freezing point method. Triphenylcarbino182"

dissolves in sulphuric acid, a carbonium ion is believed to be formed as follows:

(c6H5) 3COH + H SO COH 14. + ES o4 2 4 (c6H5 2

[ (C6H5 )3 C0H2 + ---=qC H IC+ + H30 + ESO4 H2SO4 6 5/3

In the present work the substituted cinnamyl alcohols were dissolved in 100% sulphuric acid, the sulphuric acid mixture was reacted with a large excess of water and the composition 84.

of the product was calculated by measuring the light absorption

of the final solution. The results are shown in Table XI. It was hoped in this way to generate the substituted phenylallyl carbonium ions and to study their reactions with water in order to compare the results with the hydrolysis product ratios obtained from the substituted phenylallyl chlorides. The result for the

phenylallyl carbonium ion itself may be compared with the data of Bunton et.al.84 on the reaction of the intermediate from the acid- 18 catalysed rearrangement of 1-phenylallyl alcohol with H2O It is presumed that the cinnamyl sulphuric acid, which will also undergo ready hydrolysis, is not formed.

RIOH + 2H s0 RbSO3H + HSO 2 4 4

It is believed that in such instances the oxonium ion is first formed and this reacts further with solvent to form a carbonium ion: x - c H - CH =CH - CH OH + H SO 6 4 2 2 4

X - C6H4.CH CH - 0H2OH21 + HSO4 I

X - C6H4.CH = CH - CH2OH2) + H SO 2 4 g+ 6+ X - 06H4. CH CH 1-1;- CH + H +0 + HSO 2 3 4 85.

TABLE XI

Ionization of Substituted Cinnamyl. Alcohols in 100% Sulphuric Acid, The Reaction with Water and Ethanol.

Substituent ROH ROEt (X -) ( % ) ( % )

p - Br 75.3 p - Cl 76.0 p - F 75.5 H 76.5 76.8 m - C113 78.4 p - CH 3 80.0 p - CH30 84.4

N.B. The concentration of the alcohol in the sulphuric acid

was ca 25 mg/100 ml., 2 ml. of this solution was diluted to 50 ml., with water or ethanol and the optical density measured in a 1 cm. cell. 86.

The data obtained in the present work show that the phenylallyl carbonium ion react with hydroxylic solvents at the 1-position much more readily than at the 3-position. i.e. the positive charge at the 1-carbon atom is greater than that at the 3-carbon atom, the ratio is about 3.2. Burton, Pocker and Dahn84 have studied the 18 0 exchange associated with the acid catalyzed rearrangement of

1-phenylallyl alcohol in 6* aqueous dioxan, theyfound that the intermediate involved in the rearrangement reacted with water about

1.4 - 1.5 times more rapidly at the 1-carbon atom than at 3-carbon atom. Similar results were obtained by Pocker85 in a study of the acid-catalysed deamination of 1-phenylallylamine.

Electron-donating substituents increase the reastivity at

1-carbon atom and decrease it at 3-carbon atom. This is in agreement with theory for electron donating groups which would be expected to decrease the electron density at 1-position and increase it at 3-position, while electron-att racting gdbstituentsshould cause a small increase in the electron density at 1-position and small decrease at 3-position, compared with that of the phenylallyl carbonium ion itself. 87.

B. Discussion

The results obtained in the present work for the

hydrolysis of substituted 1-phenylallyl chlorides show that

as with 1-phenylallyl chloride itself, the solvolysis occurs

by unimolecular mechanism. The rates of hydrolysis correlate

well with the Y-values, the slopes (m) of the lines are typical

for unimolecular reactions and they are in quite good agreement with the values obtained by Weinstock.

Valkanas, Waight and Weinstock showed that the rate determining step for the hydrolysis of 1-phenylallyl chloride involves ionization of the carbon-chlorine bond as shown by:

i) The sensitivity of the rate of reaction to the ionizing power of the medium.

ii) The relative insensitivity of the rate in the presence of lyate ions.

iii) The ionic strength effect and common-ion rate retardation.

iv) The formation of largely or completely racemic products in the reaction of the (+) - isomer.

In the solvolysis of substituted 1-phenylallyl chlorides, the occurrence to a considerable extent of isomeric rearrangement to the corresponding cinnamyl chloride again 88.

suggested that an ion pair is formed in the rate determining step. Presuming that the results for the ionization of

substituted cinnamyl alcohol in 100% sulphuric acid are correct, the following scheme is suggested for the solvolysis

of 1-phenylally1 chlorides.

slow c6 CH - CH = C6 4. CH CH = CH H4. 2 H 2 Cl

fas - C6H4.CH = CH - CH 2C1

C4, fEat X— C H CH'w CH ,22 CH X- C6114. CH = CH - CH OS 6 2 HOS 2 (II)

fast 1 HOS

X- C6 H4 CH - CH = CH2

OS

The first intermediate (I), i.e. the ion-pair gives

rise to cinnamyl chloride as the only stable product, i.e., it does not undergo solvolysis, and can give rise to the

second intermediate (II), i.e., the mesomeric carbonium ion

which can give rise to the two isomers. The results of 89.

18 Weinstock for the ethanolysis of 1-phenylallyl chloride

are in good agreement with the above explanation.

The activated chlorides give rise to unconjugated

ethanolysis products in approximately the amounts which were

produced from the corresponding mesomeric phenylallyl

carbonium ion (see table XI). The deactivated chlorides

give rise to amounts of unconjugated solvolysis products

which are less than those produced from the corresponding

mesomeric carbonium ion, which is very difficult to explain.

It must be born in mind that the experimental error in the

calculated product composition is 3% for the solvolysis

and approximately 4% for the ionization of cinnamyl alcohols

in 100% sulphuric acid.

The first intermediate (I) is more likely to give

rearranged chloride in the case of the activated chlorides

than for the deactivated chlorides. The results for the

ionization of cinnamyl alcohols in 100% Sulphuric were higher 84 than expected, bearing in mind the data of Bunton on the reaction of the intermediate from the acid-catalysed 18 rearrangement of 1-phenylally1 alcohol with H2 0. That is to say, the information gathered on the reactivity of the

produced carbonium ion at 1- and 3- position from the ionization of cinnamyl alcohols in 100% sulphuric acid may not be 90.

trustworthy in view of the pnviously mentioned possibility of formation of the covalent sulphuric acid. The following alternative scheme may be suggested for

the hydrolysis of substituted 1-phenylallyl chlorides.

slow X - C H 2 + 6 4 . CH - CH = CH X - C6H4 . CH - CH = CH2

Cl -C1 (I) fast H2O fast R/C1

6+ 6+ _ fast C6H4. CH = CH CH + Cl X - C H .CH - CH = CH + HC1 2 H2O 6 4 2 OH (II) fast H2O

X - C6H4 - CH = CH - CH2OH + HC1

The above scheme is the same as that proposed by 19 Valkanas, Waight and Weinstock for the hydrolysis of 1- phenylallyl chloride, the observed product ratios confirm that the behaviour of these intermediates varies with the substituent in the phenyl ring, i.e., the behaviour of the first (I) and the second (II) intermediates for each chloride differs from that of those derived from 1-phenylallyl chloride:itclf. The first intermediate °ion-pair" (I) can reaot with solvent to give rise the corresponding 1- phenyi.allyl alcohol or the corresponding cinnamyl chloride, or can give the second intermediate (II) which can give rise to the two isomeric alcohols: For the formation of the cinnamyl chloride from intermediate (I)f Weinstock suggested that a form such as

(III) is involved, either as a transition state

CH

(III) Ph. CH' 'CH2

-Cl between (I) and the final product or as an intermediate; if it were present as an intermediate, it could also lead to solvolysis products.

The results show that an electron-donating substituent in the phenyl ring causes an increase in the amount of rearranged chloride, i.e. a decrease in the degree of solvolysis. It is likely that the first intermediate (I) gives less unconjugated solvolysis product, and more rearra4ged chloride. That is to say structure (I) gives the corresponding cinnamyl chloride more readily than the second 92

intermediate; structure (III) is involved as a transition state rather than as an intermediate. The second inter- mediate (II) as in the case of the activated cinnamyl chlorides can give rise to more of the unconjugated solvolysis product than the conjugated product.

An electron-attracting substituent causes a decrease in the amount of rearranged chloride, i.e. a decrease in the degree of solvolysis. It is likely that the first inter- mediate (I) predominantly gives rise to 1-phenylally1 solvolysis products and less of the rearranged chloride; structure (III) in the deactivated chlorides may be considered as an intermediate rather than as a transition state. The second intermediate (II) as in the deactivated cinnamyl chlorides can give rise to more conjugated solvolysis product than unconjugated product.

As in the hydrolysis of substituted cinnamyl chlorides the relative rate of hydrolysis does not obey the usual

Hammett equation but it gives good correlation with 6r+ constant. This is in good agreement with the postulate that these reactions involve carbonium ion reactions, the deviation from the usual Hammett equation may be due to the resonance interaction of the para-substituent with the electron-deficient centre of the transition state43' 47,61 93.

It is suggested that for the ethanolysis of substituted 1-phenylallyl chloride, as in the ethanolysis of 1-phenylallyl chloride itself, the modified (S 1) N mechanism without nucleophilic assistance by the solvent in the rate determining step is involved. That is to say, one may consider as in the case of the hydrolysis, that two intermediates are involved, the first (I) yielding 1- phenylallyl ethyl ether, cinnamyl chloride or the second intermediate (II), which can give rise to the both isomeric ethers.

The relative rates of ethanolysis also deviate from the Hammett correlation but do not give a very good correlation with ee constants.

The deviation from Hammett equation may be due to the resonance interaction of the para substituent with the electron-defficient centre of the transition state, presuming the interaction is less than that in the hydrolysis which causes a deviation from el + constant. 94.

slow X - c H CH - CH = CH 2 ------X - C6H4.+CH - CH = CH 6 . 2 Cl (I) Cl fast R' Cl EtOH fast b+ 6+ EtOH X - C 6114. CH CH CH2 X - C6114. TH - CH = CH2 + HC1 fast + - OEt Cl Et0H fast

H X - c6 . CH = CH - CH2OEt + HC1.

As in the hydrolysis eirtron-donating groups cause an increase in the amount of rearranged chloride formed, i.e. a decrease in the degree of solvolysis. This May be due to the first intermediate (I) giving less 1-phenylally1 ethyl ether, and more of the rearranged chloride and the second inter- mediate (II) which in turn gives more 1-phenylallyl ethyl ether. Elrtron-attracting groups on the other hand causes a decrease in the amount of rearranged chloride, i.e. an increase in the degree of solvolysis. The first intermediate (I) gives more 1-phenylallyl ethyl ether and gives rise to the second intermediate which gives both the isomers with more conjugated solvolysis product. 95.

III - Isomerization of 1-Phenylally1 Chlorides

Results and Discussion

The work on the isomerization of 1-phenylallyl chloride has

already been mentioned (page 11). Table (XII) shows the rates of isomerization of p-flucro,

m-methyl and 1-phenylallyl chlorides in Nal. -dimethylformamide and in the presence of salts. It can be seen that sodium perchlorate causes

an increase in rate due to the increase in the ionic strength. Lithium chloride causes a larger increase in rate than that due to an equivalent concentration of sodium perchlorate. The p-fluoro

substituent acts as an activating group in this case as in the solvolysis reactions. It should be noticed that the rate of isomerization of 1-phenylallyl chloride determined in the present work is somewhat lower than that obtained by Weinstock as shown from the table. This may be due to an inadvertant change in the temperature.

The isomerization of the 1-phenylallyl chloride• was also carried out in N:N-dimethylformamide in the presence of a mixture of tetra-n-butylammonium chloride and perchlorate in order to maintain the same ionizing power of the mixture while varying the concentration of the nucleophilic reagent (C1'). Table (XIII) shows that the rate of isomer._lation in the presence of tetra-n-butylammonium chloride is somewhat greater than that due to an equivalent concentration of tetra-n-butylammonium perchlorate. The rate increases linearly with 96. increase of concentration of tetra-n-butylammonium chloride (Fig. VIII).

Rawiiiison and Noyes found that the accelerating effect of salts varies inversely with the size of the anion and is unaffected by the size of cation. The present work shows that the accelerating effect varies inversely with the size of the anion and that increasing the size of cation causes a small decrease.

Surprisingly fluoride ion, theoretically a more powerful nucleophile than chloride, has no effect on the rearrangement. When a solution of l-phenylallyl chloride in N:N-dimethylformamide in the presence of tetraethylammonium fluoride or tetra-n-butylammonium fluoride was kept overnight with shaking, the products had I.R. spectra showing no C-F bands, showing that neither cinnamyl nor 1- phenylallyl fluorides were present. 97. TABLE XII

Substituent Kind of Salt conc, kr X- Salt (m/1) (min 1)

m - CH 0.000 0.000498 3 LiC1 0.111 0.000973 LiC1 0.222 0.001240 NaC10 0.103 0,000835 4 Na010 0.207 0.000995 4

P - F 0.000 0.00052 LiC1 0.075 0.00081 LiC1 0.105 0.00098 NaC10 0.062 0.00072 4 NaC10 0.157 0.00085 4

H 0.000 0.000310 LiC1 0.08 0.000488 LiC1 0.16 0,000630

m H 0.000 0,000398 LiC1 0.0993 0.000544 LiC1 0.159 0,000780

a Results clue to Weinstock, 98.

TABLE XIII Isomeric rearraaGEnent of 1-phenzlally1 chloride in N:N-dimethyl formamide in the presence of mixtures of :tetran-butylammonium chloride (A) and tetran- butylammonium perchlorate (B) at constant ionic strength. Temp., 40.00C.

Salts concentration (m/1) Kr -1 A B (min )

0.000 0.000 0.000310 0.200 0.000 0.000551 0.150 0.050 0.000510 0.100 0.100 0.000475 0.050 0.150 0.000443 0.000 0.200 0.000412 0.56

0.53

0.50

0.47

0.44

0.41

0.0 0.05 0.1 0.15 0.20 Conc. of A

0.20 0.15 0.1 0,05 6.0 Conc. of B

Fig. VIII 100,

Racemization of (-)-1-Thenylally1 Chloride in N:N-dimethyl formamide.

The present work shows that (-)-1-phenylally1 chloride racemizes completely as it isomerizes in non-aqueous solvents, just as does the (+)-isomer (see page 21).

Table (XIV) shows the rates of loss of optical activity (polarimetric rates) of (-)-lphenylallyl chloride in N:N- dimethylformamide and in the presende of salts. Increasing the ionic strength of the medium, using sodium perchlorate, lithium chloride and perchlorate, was found to increase the polarimetric rate. The effect of lithium chloride on the rate is somewhat greater than that of sodium and lithium perchlorates, a linear dependence of Kpol• on the sodium perchlorate concen- tration being observed. The variation in K pol with added chloride ions was more complicated.

As with the (+)-isomer, in a solution containing up to -- 0.05 M lithium chloride the rate increases linearly and very steeply. At higher concentration the rate increase was less steep, but remained linear in salt concentration (fig.IX).

(-)-1-Phenylally1 chloride was sealed under vacuum and left overnight in an oil bath at 100°C., i.e. until all the 1-phenylallyl chloride had isomerized to cinnamyl chloride.

The product lost all its activity, i.e. the specific rotation 101. is zero in solvent or without solvent. N.M.R. and I.R. spectra showed that the product is pure cinnamyl chloride.In all kinetic runs the end values were zero. Weinstock observed a small positive value. 102.

TABLE (XIV)

Racemization of (-)-1-Phenylally1 chloride in N:N-Dimethjl formamide. The effect of added salts. Temp 40°C.

Kind of Salt conc. K salt. pol (m/1) (min-1)

0.000 0.000455 LiC1 0.0148 0.000700 Lid]. 0.0370 0.001100 LiC1 0.0660 0.001300 LiC1 0.1110 0.001680 LiC1 0.1660 0.001980 LiC1 0.2220 0.002300

NaC104 0.0344 0.000652 tl ad Oct 0.1030 0.00089 Na ti 04 0.2070 0.00135

LiC104 0.1050 0.00101 2.4 -

2.0 -

1.6 -

C) TACI O NaC/0 4 CJ LiCio 4

0.05 0.1 0.15 0.2

0 Fig. IX. • 104.

Racemization of (-)-17phenylally1 chloride in aqueous

dioxan and in ethanol-cyclohexane.

Waight and Weinstock studied the racemization of

(+)-1-phenylally1 chloride in aqueous dioxan and in(thanol-

cyclohexane. In the present work the racemization of the other

antipode was studied in order to compare the results and in

particular to check that loss of optical activity was

essentially complete.

Table (XV) shows the rate constants for the loss of

optical activity of (-)-1-phenylally1 chloride, in aqueous

dioxan and in the presence of small amounts of lithium chloride.

The polarimetric rate constant in the absence of salt exceeds

the overall spectrometric rate constant for the reaction under the same conditions, as in the solvolysis of (+)-1-

phenylally1 chloride. This gives further evidence for the

existence of the ion-pair intermediate in the hydrolysis of

1-phenylallyl chloride.

The effect of added chloride ions is to increase the disparity between the polarimetric rate and the overall rate constant. That is to say a loss of configuration may occur even when the carbonium ion recombines with the chloride ion in the 1-position. 105.

Solutionsof (-)-1-phenylally1 chloride in ethanol or in aqueous dioxan kept until all the secondary chloride had reacted, contained completely racemic 1-phenylally1 alcohol or ethyl ether, i.e, with zero rotation. Valkanas, Waight and Weinstock observed small positive values but never negative rotations, when they carried out the above experiment with the (-0-isomer and noted that the polarimeter tube filled with pure solvent had a small positive rotation from which the final readings in the kinetics runs were indistinguishable.

From the table it can be seen that the polarimetric rate constants are lower than those for the (+)-isomer, which may be due to an inadvertant change in temperature or in the medium composition. 106.

TABLE XV

Racemization of (-)-1-Phenylally1 chloride in 9047 aqueous dioxan. The effect of lithium chloride. Temp., 30.0°C.

LiC1 kpol kt ( m/1 ) (min-1) (min-1)

0.000 0.0117 0.0144 0.01535 0.0288 0.01692

0.000 0,0139 0.00971 a 0.014 0.0175 0.029 0.0193 0.01320

- Results due to Weinstock for (+)-1-phenylallyl chloride. 107.

Tracer Work.

Weinstock attempted to study the rate of exchange between labeled .Li36C1 and 1-phenylallyl chloride by partially separating the latter by distribution of the mixture of chlorides between two solvents; no useful results were obtained. Another method was adopted in the present work to calculate the rate of exchange of 1-phenylallyl chloride with Li36C1. The results 36 obtained from the exchange of cinnamyl chloride with Li Cl, and from the total exchange of 1- and 3- phenylallyl chlorides with 36 Li Cl were used. TableACVI)shows the first order rate constant for the exchange of cinnamyl chloride with Li36C1 in N:N-dimethylformamide, a linear dependence of the rate of exohange on the added label]ad lithium chloride being observed (fig. X). It seems that the exchange is bimolecular, which is in good agreement with the work of Rawlinson and Noyes liho reported that cinnamyl chloride and tetraethylammonium chloride undergo isotopic exchange in N:N-dimethylformamide by what appears to be an SN2 mechanism.

Table(XVII) shows the mean total rate of exchange of the l- and 3- phenylallyl chlorides with Li36C1. The mean first order rate constant for the overall exchange varied linearly with the added labdled lithium chloride (fig. XT), 108.

TABLE )CVI

The exchange of cinnamyl chloride with labelled lithium ahloride in N:N-dimethylformamide., Temp, 40.0° C.

Salt conc. • kexch (m / 1) (min-i)

0.0010 0.0743

0.0025 0.0745 0.0050 0.0750 0.0126 0.0763

0.0450 0.0780

0.1250 0.1020 0.1630 0.1170 0.1980 0.1260 0.14

0.13

0.12

0.11

0.10

0.09 L o.o8

0.07 36 1 I 1 t 1 1 1 Li C, Conc. 0.03 o.o6 0.09 0.12 0.15. 0.18 0.21

Fig. X

Rates of exchange of cinnam;y1 chloride with Li36C1 as a function of the concentration of added labelled lithium chloride. 110.

TABLE XVII

The total rate of exchange between 1- and 3- phenyl- allyl chlorides and labelled lithium chloride. Temp 40.000.

Salt conc. kexch. (mil) (min-1)

0.040 0.00180 0,070 0.00190 0.100 0.00195 0.135 0.00215 0.170 0.00220 0.200 0.00245 0.26

0.24

0.22.

U

N o 0.20

0.18 36 Li C1 conc. 0.04 o:o8 0.12 0.16 0.20

Fig. XI The total rate of exchange of 1- and 3- phenylallyl chlorides 36 with Li C1 as a function of the concentration of added labelled lithium chloride. 112.

The rate 3f exchange of 1-phenylallyl chloride with Li36C1 was calculated as follows: The activity in the products follows the scheme:

k ,36 k . 36 k 36 ___12 3 --_—_.11 12 Cl (II) R Cl (III) --4 R Cl (IV)

R Cl(I) ,36 k ' R Cl (V) 7.--- 1. R Cl (VI) 2 3

36

R Cl (VII) k R Cl (VIII) 3

R Cl LI) is the initial amount of 1-phenylallyl chloride in the kinetic run. R Cl(VII) is the amount of cinnamyl chloride present in the

initial sample. is the rate of exchange of 1-phenylallyl chloride k1 with Li36Cl.

k2 - is the rate of isomerization of 1-phenylally1 chloride k - is the rate of exchange of cinnamyl chloride with 3 Li36C1. the sum of the concentrations of the radioactive chlorides = + I In) (IV )

113.

This amount can be determined from the total rate

of exchange of 1- and 3- phenylallyl chlorides with Li36Cl

phenylallyl chlorides (IX) radio-active phenylallyl K4 chlorides (X) (IX) is the amount of 1- and 3-phenylallyl chlorides

i.e. I + VII [X 3 is the amount of active 1- and 3- phenylallyl chlorides.

k4 is the total rate of exchange of 1- and 3- phenylallyl chlorides with Li36C1 i.e. X7 =IIJ + + IV] ( VI) + (VIII) ... (1) ( X) = (IX) (1 - e-k4t ) (la)

i.e. the amount of the active chlorides at any time is given by equation (la). In order to estimate the other terms in equation (1) the following assumptions were .ade: Assumption (a):

1 R36Cl (xi) R Cl (I) R Cl (XII) k2-7 i.e., the 1-phenylallyl chloride exchanges to give active 114.

1-phenylallyl chloride only and rearranges to give inactive cinnamyl chloride only.

The reaction is simple first-order as far as R el (I) is concerned.

• • _ d(I)t _ k2 = (k1 k2) 1 i)

I) -(k1 + k2)t [IJ t L

I ) is the amount of 1-phenylallyl chloride after time t. Also,

d (lc k )t I xi) - k 1 2 dt 1 I) t = k1 II) e-

k • • f 1) -(k + k )t • • xi _ k11 ( 1 - e 1 2 ) + constant..(2) + k2

the constant is the amount of (XI) at t = 0, i.e., the constant = 0.

Thus the amount of active 1-phenylallyl chloride can be estimated from equation (2).

115.

Assumption (b):

2 ,36 R Cl (I) R Cl (XIII) --== R Cl (XIV)

i.e. assuming that 1-phenylallyl chloride gives inactive cinnamyl chloride then the latter undergoes exchange to give active cinnamyl chloride.

11) (13 e-k2t

. k2 -k t -k t xiii ) i )- ( e 2 - e 3 ) k3 k2

(e-k2t -k3t ••• (XIV ) = - (I ) e-k2t + fki) - 2 - e .. (3) 3 k k2

The active cinnamyl chloride (VIII) produced from the cinnamyl chloride (VII) present initially in the sample can be estimated from equation (4)

-k t (VIII) = (VII) (1 - e 3 ) (4)

Substituting in equation (1): 116.

)t t fl k1 -(k-+ k2 e -k Cl - 2 k e 1 + k2 /

k -k t -k t -kit [I) 2 2 3 k e - e )).] + (1 e 3 - k2

(.IX) (1 - e-k4t ) 1

So k1 can be determined at any selected time t. Table XIX shows the calculated rate of exchange of 1-phenyl- allyl chloride with Li36C1 at t = 100 mins. It can be seen that the rate of exchange is equal to the rate of racemization.

Such a result is explicable only in terms of an intermediate which undergoes exchange with an equal probability of producing each optical antipode, i.e. an ion-pair in which the carbonium ion can be attacked with equal ease from each side. Az. shielding of attack from one side by the chloride ion originally bound would result in a larger rate of racemization, which in the extreme case of exchange by the bimolecular mechanism would be twice the rate of exchange. It can thus be concluded that over the range of LiC1 concentration used (0.04 - 0.2 mole /1 .) the exchange-racemization-rearrangement process involves an ion- pair intermediate which can return to 1-phenylallyl chloride as rapidly as it forms cinnamyl chloride. 117.

TABLE XVIII

The rates of racamization and the calculated rate of exchange of 1-Thenylally1 chloride with Li3601.

36 k Li C1 kexcill rao. (conc. m/1) ( min ) (min )

0.040 0.000972 0.00075 0,070 0.001020 0.00093 0.100 0.001050 0.00108 0.135 0.001073 0.00116 0.170 0,001090 0.00132 0.200 0.001340 0.00137

118.

IV - Rearrangement of 1-phenylally1 p-nitrobenzoates.

Results and Discussions The isomerization of 1-phenylallyl p-nitrobenzoate has been shown to involve both a unimolecular and a bimolecular reaction with p-nitrobenzoic acid. Braude, Turner and Weight showed that the former was intramolecular 'in not producting equilibration of carboxyl- oxygen atoms. Pooker on the other hand claimed that the reaction involves ionization in the rate determining step (SN 7). (See page 24-30). In an attempt to gather further information on the mechanism of 1-phenylallyl p-nitrobenzoate a study of the effect of a aubstituent in the phenyl ring was made. A series of substituted 1-phenylallyl p-nitrobenzoates (I) and cinnamyl p-nitrobenzoates (II) were prepared. The rearrangements of (I) to (II) were carried out thermally in non- aqueous solvents, chlorobenzene at 130°C and N:N-dimethylformamide b at 110 C, and the reabtion rates studied spectrokinetically.

X - C . CH - CH m CH2 X - C H CH . CH - CH 6 H4 6 4° 2 0.00,CH NO 0. CO. C6H4NO2 4 2

(X m p -Br, p-Cl, p - F, H, m•CH3t p - CH3 and p-C11.30). 119

This work was undertaken to confirm and extend the preliminary investigation made by Harris,86 The first order rate constants are shown in the tables ( XIX , XX ). It can be seen that in both solvents the rate of isomerization increases in the sequence p-Br

Hammett equation but give better correlation with a + constants, From the shape of the curve of the Hammett correlation, it can be seen that the best lines through the activated points and the origin have higher slopes (m) than that for the deactivated points. This behaviour suggests that more than one mechanism is involved and that rearrangement of the activated esters is more likely to be SIT 1 in character while that of the deactivated esters is likely to be intramolecular. 120.

TABLE XIX. Isomerization of Substituted 1-phenylally1 p-nitrobenzoates in chlorobenzene, Ester conc. ca. 0.16 M., Temp., 130°

Substituent K ( min 1 )

p - Br 0.000034 p - Cl 0.000059 P - F 0.000072 m H 0.000100 m - CH 0.000133 3 p - CH 0.000700 3 p - CH 0 0.018000 3

Results due to Braude Turner and Waight. Log k/ko 2.4

p - CE 0 3 1 2.0

1 1.8 1 1 1 1

-1.0

p - CH 3 _ o.6

0.2 + m - CH 0.3 a or a 3 0.1 0.2

o.8 0.7 o.6 0.5 o.4 0.3 0.2 0.1 0 P Fig. XII 0.2 p Cl 0.4 - - - The relative rates of isorierization of substituted p - Br 1-phenylallyl p-nitrobenzoate in chlorobenzene at 0.6 130C versus a ( 0 ) and a ( O ) . H N • H • • 122.

TABLE XX.

Isomerization of substituted 1-phenylallyl p-nitrobenzoate in N:N-dimethylformamide, Ester. Conc. Ca. 0,015-0.007,M Temp., 11000.

Substituent K -1 (X) ( min )

p - Br 0,00002 p- 01 A0.00003 p - F 0.000078 H 0.000087 m - OH 0.000111 3 p - CH . 0.000682 ) p - CH30 0.017000 Log k/ko

2.4

p - C1130 - 2.0

,1.6

p - CL13 • -0.8

a or a - CH 0.1 0.2 3

0.8 n.7 n.6 0.5 0.4 0.3 0.2 0.1 p - F Fir.. XIII 0.4 - p Cl The relative rates of isomerization of substituted 1-phenylallyl p-nitrobenzoate in N:N-dimethylformamide at 1100C versus Q (0 ) and cr + (Q ). o.8 124.

V. Attempts to pr pare 1-pherglallylamines. 26 Valkanas and Waight studied the reaction of 1- and 3-phenylallyl chlorides with di- and tri-ethylamine, and found that the unconjugated amine or the quaternary salts are formed first and then rearranged to the cinnamyl isomers under their experimental condition.

It was hoped to prepare a number of 1-phenylallyl- amines and investigate their rearrangement and deamination reactions.

A number of possible routes to the required amine were investigated by Boxer and are described in turn. The preparation of 1-phenylallylamine by the following route has 85 been claimed by Pocker .

125.

A Ph. COMB CH2O Ph.CO. CH2.CH2.NMe2 HC1 Me2NH2Cl steam H2O

NH OH Ph.C.CH = CH 2 2 Ph.CO. CH = CH2

N OH LIT

Ph. CH. CH = CH2 Ph. CH. CH = CH2

NH2 NR2

87 Attempts made by Boxer to oximate the ketone were unseccessful and the product was that of 1,4—addition, namely:

Ph. CO. CH2. CH2

NO H

Ph .CO .CH2.CH2 as recorded by Casey and Marvel88.

126.

me B PhoCOM0 Ph.CO.CH2.CH2oN 2.11C1

Ph. C. CH = CH2 Ph. CO. CH = CH2

NPh LAH

Ph. CH. CH = CH2 ' Ph. CH. CH = CH2

NHPh NRPh

It was hoped that the action of aniline on phenyl vinyl ketone would be to form an anilide, as with simple ketones. Boxer found that the product was /3-anilino- propiophenone.

C as before Ph. COMe Ph. CO. CH2.9112"NMe2.BC1

NH2OH — Ph.C.OH2sv112 MeI Ph. C. CH2.CH2. NMe2 it NOH NOH NaOH

1AH Ph. C. CH = CH 2 Ph. CH. CH : CH2 I NOH NH2 127.

89 The Mannich base oxime was prepared in accordance

with the literature. The methiodide was then prepared by adding excess methyl iodide to a methanolic solution of the oxime. The methiodide was reported to yield the unsaturated oxime in 14% yield, as first reported by Kyi and Wilson90,

when the methiodide was treated with aqueous sodium

hydroxide, no concentration details or reaction times being given. More information has recently been published91 in which

the conditions for the aqueous reaction were described as

"a tenfold excess of sodium hydroxide", the yield was quoted as 58%.

Boxer prepared the phenyl vinyl ketoxim6 but he did not attempt to reduce it to the corresponding amine.

In the present work the phenyl vinyl ketoxime was prepared as shown above and the reduction of the oxime with lithium aluminium hydride was carried out under various experimental conditions. The only product obtained was the imine

Ph. CH - CH - CH 3

H

This structure follows from the n.m.r. spectrum which showed bands with the following values:

128.

CH : 9.2 (doublet) 3 N - H: 8.2 (broad)

C - H: 7.73 (multiple), 6.9 (doublet) Ph 2.8

In the present work two other routes have been

examined 1r hexamethylen D amin th. CH. C CH Ph. CH - C CH CL NH HNEt2 2 Pd/H2 • Ph. CH - C CH Ph. CH.. CH = CH2

NH N Et2 2 Pd/ H 2

Ph. CH - CH = CH2

NEt2

It was hoped to prepare the corresponding amine from

the reaction of phenylethynylcarbinyl chloride with

diethylamine or with hexamethylenetetramine92. In fact only mixtures of unidentified products were obtained. 129.

Ph. C + CH CH MgC1 Ph. CH. CH = CH 2 2

NR NHR

Attempts were made to prepare 1-phenylallylamine from the reaction of vinylmagnesium chloride, prepared according to the method of Rosenberg et a193, with benzylidene ethylamino94 only hydrolysed aldimine or the aldimine were obtained under various experimental conditions.

Presumably the vinylmagnesium chloride is unreactive under the experimental conditions which were adopted. 130.

EXPERIMENTAL 131.

Preparation

1-Phenylally1 Alcohol To a well stirred solution of phenyl magnesium bromide - prepared from bromobenzene (157 g.) and magnesium (24. g.) in anhydrous ether (400 ml.) maintained at -10°, a solution of acrolein

(67 ml.) - freshly fractionated through 30 inch column packed with Fenske-Helibes - in anhydrous ether (100 ml,), was prided dropwise during 2 hours, Stirring was Continued for an other 3 hrs. and the complex was then debomposed with 5% sulphuric acid (200 ml.) to avoid the formation of the gelatinous layer. The ethereal layer was separated washed three times with water, dried (KHCO3), filtered and distilled. After two fractional distillations the product (80 g) 17 p X had b.p. 85°/ 3 mm., ri 1.5460, max 2520 .(€750).

N.M.R. spectra showed that this product was contaminated with unidentified impurities, so that for further purification, the alcohol was converted to the hydrogen phthalate as follows: The alcohol (67 g.) was added to a suspension of phthalic anhydride (74 g.) in dry pyridine (45 g.). The mixture was stirred for 4 hrs. at 50°, the resulting yellowish, clear, syrupy solution was diluted with ether (200 ml.), washed up five times with ice- cold 2N-hydrochloric acid and the solvent evaporated. The resulting semi-solid mass was treated with a large volume of ice and dilute 132. hydrochloric acid. After being allowed to stand for a short time it yielded solid material (105 g.), m.p, 63 - 70°, which was dried and recrystallized three times from carbon disulphide - light petrol to m.p. 73(lit.95 m.p, 75-74o). The hydrogen phthalate was reduced to the alcohol as follows: A solution of lithium aluminium hydride (13.7 g.) in anhydrous ether (830 ml.) was added dropwise to a well stirred solution of the hydrogen phthalate (50 g.) in anhydrous ether (700 ml.) at -10°. The addition was carried out during 3 hr., the mixture was then stirred for a further 2 hrs. at 001 then it was decomposed by addition of saturated ammonium chloride (200 ml.) The ether layer was washed with water, dried over (KHC05) and the solvent evaporated. The product was fractionally distilled, and the fraction (15 g.) boiling at 105.0°/9.5 mm, was collected. It had n1021 1.5404,

Amax. 2520.. (:185) (Lit.° h 1025 1.5386, X _max. 2520 (e187)). p-Bromo-l-phenylallyl alcohol.

p-Dibromobenzene (50 g.) in anhydrous ether (100 ml.) was added dropwise to a suspension of magnesium (5 g.) in aihydrous ether (100 ml.) containing ethyl bromide (0.2 ml). Stirring was continued with refluxing fDr 24 hrs, and then freshly distilled acrolein (13 g.) in anhydrous ether (40 ml.) was added during 2 hrs. 133.

o at -10 stirring being continued overnight. The complex was then decomposed with ice-cold saturated aqueous ammonium chloride (200 ml.)

and the product worked up in the usual manner. After five fractional distillations the product obtained was unchanged

p-dibromobenzene (10 g.) and p-bromol-phenylally1 alcohol (16 g.),

b.p. 90-910 / 0.2 nun. , 20 1.5712, Amax 2590 (€980).

(Found: C, 51.00; H, 4.41; Br, cal, for C H OBrC, 50.72; 37.65; 9 9 H, 4.25; Br, 37.507).

p-Chlmri-phenylally1 alcohol.

p-Bromochlorobenzene ,(25 g.) in anhydrous ether (50 ml.)

was added dropwise to a suspension of magnesium (3.2 g.) in anhydrous ether (50 ml.) containing ethyl bromide (0.2 ml); stirring was continued for 4 hrs. in an atmosphere of nitrogen. Freshly distilled acrolein (7.8 ml) in anhydrous ether (30 ml.) was added

dropwise at -10° and, after stirring overnight, the complex was decomposed with ice-cold saturated aqueous ammonium chloride (200 ml.)

The ethereal layer, which was separated by centrifuging the mixti)re, was washed with water and worked up in the usual manner. Three fractional distillations yielded p-chlorol-phenylally1 alcohol (14 g.).

b.p. 80-81°/0.3 mm., n3018 1.5518, Amax. 2580 .R (E860)

(Lit.29 b.p. 125-128° /12 mm. 134.

p-Fluoro-l-phenylally1 Alcohol

p-Bromofluorobenzene (25 g.) in anhydrous ether (5o m'.)

was added dropwise to a suspension of magnesium (3.5 g.) in anhydrous ether (50 ml.) containing ethyibromide (0.2 ml.). Stirring

was continued for 4 hrs. in an atmosphere of nitrogen and then freshly distilled acrolein (10 ml) in anhydrous ether (30 ml.) was

added during 2 hrs. at - 10°. After stirring overnight, the complex was decomposed with ice-cold saturated ammonium chloride (200 ml.)

and the ethereal layer, which was separated by centrifuging the

mixture, was worked up in the usual manner. After three fractional p-fluoro 1-phenylallyl alcohol (14 g.) had b.p.

68 - 70(1/4.4 mm., riD18 1.5154, max. 2520 R (c 750). np22.5 1.5137) (Lit." b.p. 82-84°/ 3 min.,

m-Methyl-l-phenylallyl alcohol

Freshly distilled acrolein (10 ml.) in anhydrous .ether

(40 ml.) was added during 2 hrs. to m-tolyl magnesium bromide prepared from m-tolyl bromide (26.7 g.) and magnesium (3.6 g.) in

anhydrous ether (50 ml.) - maintained at -10°, after Which the solution was stirred for a further 3 hrs. and then treated with cold saturated solution of ammonium chloride (200 ml.). After isolation

of the product in the usual manner, m-methyl 1-phenylallyl alcohol (12 g.) was obtained by fractional distillation. It had 135.

b.p. 700/ 1 mm., n3121 1.5355, ax. 2560 (*).: 810). (Lit29, b.p. 115-117°/ 11 mm.).

p-Methyl-1-phenylally1 alcohol.

Freshly distilled acrolein (1.0 ml.) in anhydrous ether (40 ml) was added dropwise to a well stirred solution of p-tolyl magnesium bromide - prepared from p-tolylbromide (25 g.) and magnesium (3.6 g.) - in anhydrous ether (60 ml.) during 2 hrs. The solution was stirred for a further 3 hrs. and treated with ice-cold saturated ammonium chloride solution (200 ml.). Isolation of the product in the usual manner gave, after three fraetional distillations, m-methyl 1-phenylally1 alcohol (15 g.) b.p. 77-78° / 0.3 mm., 21 1018 1.5370, Amax 2570 i (E890). (Lit.97 b.p. 120-122°/ 10 mm.)

P-Methoxy-l-phenylally1 alcohol.

Redistilled p-bromoanisole (28 g.) in anhydrous ether (50 ml.) was added dropwise to a suspension of magnewium (3.6 g.) in anhydrous ether (50 ml.) containing ethyl bromide (0.2 ml.), stirring being continued overnight in an atmosphere of nitrogen. Freshly distilled acrolein (10 ml.) in anhydrous ether (50 ml.) was added during 2 hrs, and the mixture then treated with ice-cold saturated ammonium chloride solution (200 ml.). Working up in the usual manner, gave after three fractional distillations p-methoxyl 1-phenylally1 alcohol 136.

20.51.5470, 2561 (13.5 g.), b.p. 96-98°/0.4 mm., nip max (Q1700).

Cinnamyl alcohol.

Commercial cinnamyl alcohol was recrystallized from ether- pentane. It had X 2510 18.180). (Lit x 2510 2 max c 9.6 max . ( 17,900)) .

2-Bromacinnamyl alcohol

A solution of p-bromo -1 -phenylallyl alcohol (2 g.) in 60% aqueous acetone (150 ml.) was made 0.2 N with HC1. The mixture was then refluxed on steam bath for 72 hrs. After evaporating the acetone, the product was isolated in ether, dried over (146,S0 ) 4 ' filtered and the solvent was evaporated. A quantitative yield of p-bramocinnamyl alcohol was obtained, which on recrystallisation from methanol, had m.p. 67; 2580 24,000.(Found: Xmax ( C, 50.69; H, 4.30; Br, 37.17. Cal. for C H BrO, C, 50.72; 9 9 H, 4.25; Br, 37.5(1). p-ohlorocinnanyl alcohol.

A solution of p-chloro-l-phenylallyl alcohol (2 g.) in 60% aqueous acetone (150 ml.) was made 0.2N with HC1. The mixture was then refluxed for 72 hrs. and worked up in the usual manner, from 137.

0 pet-ether (40-60 ). A quantitative yield of p-chlorcastrinamyl alcohol 0 was obtained. It was recrystallized from pet ether (40-60) and had 0 2560 29 m.p. 57, X'max. R 22,000). (Lit. m.p„ 57-58°).

p -Fluorocinnamyl alcohol.

p-Fluaro-l-phenyl alcohol was converted to p-fluorocinnamyl 0 alcohol as shown above. Recrystallized from pet-ether (40-60), it had m.p. 57: Amax 2500 R (e 17,900). (Found: C, 70.83; H, 6.07; Cal for C9H9OF, C, 71.03; H, 5.962).

m-Methylcinnamyl alcohol. m,llethyl-l-phenylally1 alcohol was converted to the corres- ponding cinnamyl alcohol as shown above. After fractional the alcohol separated as a colourless, mobile oil, which could not be induced to solidify. After distillation it had b.p. 96-97/0.2 mm., 2545 (e 17,300). Xaxm .R b.p. 137-140°41 mm.).

p-Methylcinnamyl Alcohol A mixture of p-methyl-l-phenylallyl alcohol (5 g.) and acetic anhydride (5 ml.) was boiled for 6 hrs, and then distilled. The acetate, which had b.p. 85-88°/ 0.3 mm., was boiled for 3 hrs. with 100 g. of 5% alcoholic potassium hydroxide. The product was isolated 0 with ether, and after three recrystallizations from pet-ether (40-60) 138.

(yield 3.0 g) had m.p., 50-51°, Xmax 2540 20,300).

(Lit,97 m.p. 51-520). n-Methoxycinnamyl alcohol

p-Methoxy-l-phenylallyl alcohol( 3 g.) was converted to p-methoxycinnamyl alcohol as shown above. After three recrystal- lization the alcohol (2 g.) had m.p., 80° X 2610 .1? max. (€ 22,230). (Found: C, 73.23; H, 7.46, Cal. for C10H1202C'73.15; H, 7.36Z).

1-Phenylally1 chloride

This was prepared by the method of Valkanas and Waight.

Pure 1-phenylallyl alcohol (13.4 g., 0.1 mole) was added to a solution of triethylamine (12.1 g., 0.12 mole) in absolute chloroform (150 ml.). The mixture was cooled to -10° and a solution of thionyl chloride (13.1 g., 0.11 mole) in absolute chloroform

(10 ml.) was added dropwise with stirring during thirty minutes and the stirring continued for a further ten minutes. The solution was then quickly washed with ice cold water, then three times with saturated aqueous sodium hydrogen carbonate solution and then with ice-cold water again. It was dried (MgS0 )for two hours. The 4 chloroform was evaporated under oil-pump vacuum using a trap cooled in solid CO 2' and crude chloride consisting of 1- and 3- phenylallyl 139.

chlorides was rapidly fractionated three times, the higher boiling

point fraction being discarded on each occasion. The purest sample

obtained had b.p., 32-33°/ 0.1 ram., IlD22 1.5410, Xmax 2530 ( E 632). (Lit.2°, n1022 1.5420, ?'lmax 2530 R (E 1900), n022 1.5410,

max 2530 R (E602)). The chloride could be kept in a stoppered tube under liquid nitrogen.

Cinnamyl Chloride

To a well stirred solution of cinnamyl alcohol (13.4,

0.1 mole) in dry pyridine (8 ml.), maintained at 0°C, a solution of thionyl chloride (13.1 g., 0.11 mole), in dry ether (25 ml.) was

added dropwise, stirring being continued for one hour after the addition. The ether layer was washed with saturated aqueous sodium hydrogen carbonate solution until it was neutral, and then dried

(Ngs04). After evaporation of the ether, the product was twice

distilled, a centre portion being retained. The sample used had 30 / 0.1 lam., 25 b.p. 51-5 X 1.5815, Xmax 2530 R (6 19,300). Lit.17, max. 2530 RI (IF 20.000)).

1- and 3-p-Bromophenylallyi chlorides

The method of Valkanas and Waight was adopted for this preparation. The purest sample obtained from the head fractions which are rich in p-bromo-l-phenylallyl chloride, had b.p. 85-88°(.2 mm., 140.

20 /ID 1.5830, Amax. 2610 2 (ri 5,000), (Found: C, 46.85; H, 3.74; Cl + Br, 50.20. Cal, for C1H8Br01, 0, 46.67; H, 3,49; Cl + Br,

49.8a) The purest sample obtained from the tail fractions 97-98/0.2 mm, which is pure p-bromooinnamyl chloride after recrystallization from pet-ether (40-60)had m.P. 57-58°, Amax. 2610 2 Os 24,000). (Found: C, H, 3,81; Cl + Br, 50.44. Cal. for BTU, 46.549; c9II8 C, 46.67; H, 3.49; Cl + Br, 49.860.

1- and 3- p-chlorophenylallyl chlorides

These were prepared as described previously, from the reaction of p-chloro 1-phenylally1 alcohol with thionyl chloride in chloroform in the presence of triethylamine. The purest sample obtained from the head fractions, which are rich in p-ohloro-l-phenylally1 2 chloride,lad b.p., 60-61°/0.1 mm., 11D22 1.5530, 7,111am 2570 OE 1800). (Fauna: C, 57.57; H, 4.38; Cl, 38.06. Cal, for

C9 H 8 Cl 2 , C,57 71*, H 4.39'7 Cl, 37.84) The purest sample obtained from the tail fractions, b.p. 72-73°/ 0.1 mm., which is pure p-ohlorocinnamyl chloride, recrystal- lized from pet-ether (30-46), had m.P. (e 9 440, Amexm 2570 22,600), (Found: C, 57.37; H, 4.26; Cl, 37.86. Cal. for C9H8C12, C, 57.71; H, 4.39; Cl, 37.882). 141.

1- and 3- p-fluorophenylallyl chlorides These were prepared by the usual way from the reaction of p-fluoro-l-phenylallyl alcohol. The purest sample obtained from -11 the head fractions which are rich in p-fluoro-l-ph lallyl chloride,

had b.p. 35-36° / 0.15 mm., np18 1.5082, Xmax. 2520 R 980). (Found: C, 63.6 ; HI 4.77; F, 11.15. Cal. for C9H8C1F, C, 63.39; H, 4.72; F, 11.20X) The sample obtained from the tail fraction, which is pure riD21 1.5490, p-fluorocinn amyl chloride, had b,p. 44.45° /0.2 ram., Xmax. 2520 R 18,400). (Found: C, 63.24; H, 48.5; F, 11.44. Cal. for C H CIF, C, 63,39; H, F, 11.152) 9 8 4,72;

lr and 3- m-t43thylphenylally1 chlorides. These were prepared from m-methyl-l-phenylallyl alcohol by the method of Valkanas and Waight. The purest sample of m-methy1-1- phenylallyl chloride obtained had b.p. 68-72/0.3 mm., rip 221.5211, Nmax 2560 Oa 2,000). (Found: C, 71,61; H, 6.61; Cl, 21.43. Cal. for C10H11C1, C, 72.00; H, 6,65; Cl, The purest sample of m-methylcinnamyl chloride obtained had

b.P. 77-78°,(0.3 mm., np22 1.57501 Nmax. 2560 (C 17,800). (Found: C, 73.36; H, 6.96; Cl, 21.83. Cal for C 10H11C1' C, 72.00; H, 6.65; Cl, 21.34). 142.

p-Methoxycinnamyl chloride

p-Methoxy-l-phenylaly1 alcohol (8.2 g., 0.05 mole.) and thionyl chloride (7.1 g., 0.06 mole) were dissolved in anhydrous ether (500 ml.). The reaction was followed spectrometrically; p-methoxy-l-phenyladly1 chloride initially produced isomerized to the conjugated chloride before the reaction of the alcohol was completed.

The mixture was washed with ice-cold water, saturated aqueous sodium hydrogen carbonate and ice-cold water again. The ether layer was dried (M04) and the solvent evaporated. p-Methoxy cinnlmyl chloride obtained after three recrystallizations from pentane, had m.p., 66-67°, Xmax 2705 R OE 23,300). (Found; C, 65.55; H, 5.88;

Cl, 19.44. Cal for C10H11 C10, C, 65.8; H, 6.07; Cl, 19.a)0 p-Methylcinn.amyl chloride.

This was prepared by the above method from the reaction of p-methyl-l-phenylallyl alcohol with thionyl chloride in anhydrous ether. The reaction was followed spectrometrically and the product isolated in the usual manner. After three reorystallizations from pentane, p-methylcinnamyl chloride had m.p. 39-40°, 2k.ax 2570 R, m (G, 21,000). (Found; C, 72.19; H, 6.74; Cl, 21.58. Cal. for

CloHi1C11 C, 72.00; H, 6.65; Cl, 21.34). Attempts were made to prepare the m-methyl-l-phenylallyl chloride according to the method of Valkanas and Waight, but only m-methylc inn amyl chloride was obtained. 11+3.

Substituted cinnamyl ethyl ethers. The following procedure adopted for the preparation of each ether: Substituted cinnamyl chloride (0.02-0.03 mole) was added to a 2N solution of sodium ethoxide in ethanol (50 ml.) and the mixture boiled under reflux for two hours, added to water (50 ml.), and extracted with ether. The ethereal extracts were dried (Ngsolt) and distilled. After fractional distillations, each ether has the following physioal constants.

b.p. °C 24 7 nax.R p-Br 110-1110/0.5 mm. 1.5702 2590 23,500 p-Cl 105-106c)/ 1 mm. 1.5383 2570 20,100

10-11 72- 73°/0.3 mm. 1.5146 2520 18,200 m-CH 82 - 83°/0.4 mm. 16,300 3 1.5353 2545 p-OH3 82-83 °/0.3 ma. 1.5.340 2540 19,:500 p-0H 0- 110-1127 0.2 mm. 3 1,5393 2610 20,500

(-)-1-Phenylally1 chloride

The quinidine salt of (t)-1-phenylally1 hydrogen phthalate has been prepared by Weinstock as a bulky mass of solid material. After being recrystallized thrice from methyl acetate in order to separate as muoh of the salt of the (-)-acid ester as possible, the liquors were left to stand for a fortnight and then deposited compact salt glassy crystals of the quinidineAof the (+)-hydrogen phthalate. After one recrystallization from acetone the latter yielded the 0 optically pure quinidine salt (50 g,), m.p. 161-163 (decomp.), 19 o [ jD + 113.1 (in chloroform). (Lit.95'96, m.p., 161-163 decomp.), [ J D + 106.8°, 1, 2; c, 5.101 in chloroform).

The quinidine salt (50 g.) of m.p. 161-163°, was covered with acetone(100 ml.) and decomposed with cold dilute hydrochloric acid (ca. 5%) in slight excess. The solution was extracted with

ether, washed with water, dried (M O4) and the solvent evaporated. The residue, (-)-1-phenylally1 hydrogen phthalate (21 g.) was a light yellow semi-solid viscous oil, which could not be induced to D21 crystallize. It had [a] 47.1° (in chloroform). (Lit",

a] D - 42.3° L, 2; c, 4.947 in carbon disulphide.) ( The hydrogen phthalate was reduced to the alcohol according to the method of Duveen and Kenyon. (-)-1-Phenylally1 hydrogen phthalate (21 g.) was treated with 5M-potassium hydroxide in 50% aqueous ethanol (200 ml.) and, stirred overnight. The liberated (+)-1-phenylallyl alcohol, removed by steam distillation (6.7 g.) 0 had b.p. 56-57°/2.5 mm., np19 1.5399; aD23 + 9.0, 1,, 1. 95 61 aD19 maxax 2520 R (q_683). (Lit. 19 20; 1, 2). The optically active chloride was prepared by the method 145.

of Valkanas and Waight., from (+) -1 -phenylallyl alcohol (6.7 g.). The ( -) -1 -phenylallyl chloride obtained (2.1 g.), had b.p. 30.0°/ D21.5 18.5 0.1 mm., [a) - 14.250; np 1.5440, Xmax. 2520 R (€ 1700).

1- and 3-p-lroLlcplaenylally1 p-nitrobenzates.

p-Bromo-l-phenylallyl alcohol (6.0 g.) was added to a suspension of p-nitrobenzoyl chloride (8 g.) in dry pyridine ( g ml), at 0°C. After two days at room temperature the mixture was poured into excess of ice-cold water. The p-bromo-l-phenylallyl p-nitro- benzoate (9 g.) was filtered off, washed with water and recrystal- lized from methanol. It had m.p. 68°, Xmax 2590 R, (E13,700). (Found: C, 52.35; H, 3.51; N, 4.06; Br, 22.08. Cal. for C16H121163 Br, C, 52.48; H, 3.33; N, 3.86; Br, 22.06Z).

p-Bromocinnamyl p-nitrobenzoate was prepared as above from n-bromocinnamyl alcohol and p-nitrobenzoyl chloride, and recrys- tallized from ethanol, had m.p. 129-130, X ax 2595 R OE 37,900). m • (Found: 0, 53.08; H, 3.18; N, 3.96. Cal. for C161112NO3Br, C, 52.48; HI 3.33; N, 3.862).

2-L a.nd lllp-nitrobenzoates p-Ohloro-l-phenylally1 alcohol (7.4 g.) was added to a suspension of p-nitrobenzoyl chloride (9.2 g.) in dry pyridine ( g ml.) at 146.

0°C. After working up by the usual manner, the p-chloro 1-phenylallyl p-nitrobenzoate (10 g.) was washed with water and crystallized from methanol. It had m.p. 80-81°, Amax 2575 . (E 13,650) (Lit.29, m.p. 81-82°). p-Chlorocinnamyl p-nitrobenzoate was prepared as above from p-chlorocinnamyl alcohol. It was recrystallized from ethanol, m.p. 130-131°, X 2585 (E 37,400). ( max. . Lit.29 m.p. 130-131°).

1- and 3-p-Fluorophenylallyl p-nitrobenzoate

'p-Fluoro 1-phenylallyl alcohol (8 g.) was added to a suspension of p-nitrobenzoyl chloride (9 g.) in pyridine at 0°C. After working up as usual, the p-nitrobenzoate (10 g.) was recrystal- lized from methanol. It had m.p. 47-48°, max 2540 (: 13.400).

p-Fluorocinn amyl p-nitrobenzoate was prepared as above from p-fluorocinnamyl alcohol. The p-fluorocinnamyl p-nitrobenzoate, recrystallized from ethanol, had m.p. 100-101°. max 2545 R (€ 33,700). (Found: c, 63.90; H, 4.06; N, 4.79. Cal, for c1el12N63F, C, 63.57; H, 4.33; N, 4.61).

1- and 3- m-Methyl phenylallyl p-nitrobenzoate. These esters were prepared by the usual method from the reaction of 1- or 3- m-methyl phenylallyl alcohol with p-nitrobenzoyl chloride. The m-methyl-1-phenylallyl p-nitrobenzoate, recrystallized 147.

frotu methanol, had m.p. 5 R, ('a 2-53°,Xmax 2565 13,300). (Lit.29, m.P. 53). The m-methyl-cinnamyl p-nitrobenzoate, reorystal- lized faamethanolo had m.p. 63°, A. max 2570 (E33,000). (Lit.29, m.p. 63-64°).

1- and 3- p-Methyl-phenylally1 p-nitrobenzoates.

p-nitrobenzoates were prepared by the usual pyridine method from p-methyl-l-phenylallyl alcohol (3 g.) and p-nitro benzoyl chloride (4 g.). p.Methyl-l-phenylally1 p-nitro- benzoate (4.5 g.) was recrystallized from methanol. It had m.p., o 81-82 xmax.2575 R 13,600). (Lit.97, m.p. 82°).

p-Methylcinnamyl p-nitrobenzoate was prepared by refluxing a mixture of p-methyl-l-phenylallyl p-nitrobenzoate in acetic anydride for 6 hrs. which was then poured into ice-cold water. The precipitate after being washed with water and cold alcohol gave, after recrys- tallization from ethanol, pure m-methylcinnamyl p-nitrobenzoate (0.7 g.)

It had m.p. 132°, Amax. 2580 (C 35,000). (Lit.97, m.p. 131-132°).

1- and 3- p-Methoxy-phenylallyl p-nitrobenzoates

p-Methoxy-l-phenylallyl p-nitrobenzoate was prepared by the usual pyridine method from p-meth7oxyl-phenylally1 alcohol (4.1 g.) and p-nitrobenzoyl chloride (4.3 g.). Separating of the product in the usual manner, yilded p-methoxy-l-phenylallyl p-nitrobenzoate, 11+8.

(2.5 g.) which was recrystallized from pet-ether (40-60°). It had m.p. (Found: C, 67°, Xmax. 2640 R ( 15,500). 64.91; H, 5.13; N, 4.53. Cal. for c H N0 , C, 5.19; H, 4.8; N, 17 15 4 4.4).

p-Nlethoxycinnamyl p-nitrobenzoate was prepared by heating a solution of p-methoxy-l-phenylallyl p-nitrobenzoate (0.5 g) in

N:N-dimethyl formamide (3 ml.) for 12 hrs. at 130°, and then pouring the solution into cold ethanol. The precipitate was pure p-methoxycinnamyl p-nitrobenzoate, m.p. 131-132, Xmax. 2645 R, (' 38,100). (Found: C, 64.91; H, 4.85; N, 4.47. Cal, for C17H15N04, C, 65.19; H, 4.80; N, 4.4).

(1-Dimethylaminoprorliophenone Hydrochloride

To aceto:7- phenone (60 g., 0.05 mole), dimethylamine hydrochloride (53 g., 0.065 mole) and paraformaldehyde (20 g.,

0.022 mole) was added, concentrated HC1 (2 ml.) in 95o ethanol

(160 ml.), and the whole refluxed for 2 hrs. Acetone (800 ml)was added to the hot, clear, yellow solution and the mixture allowed to cool down to room temperature. It was then left over-night in the refrigerator. The solid product which separated was filtered off (80 g.), washed with acetone and dried for 2 hrs. at 50-60°C. It had m.p. 153-154.° (Lit.98, 155-156°). 149.

p-Dimethylaminortrophiophenone Oxime. p-Dimethylaminopropiophenone hydrochloride (17.6 g.,

0.08 mole) and hydroxylamine hydrochloride (16.4 go, 0.24 mole) were dissolved in water(20 ml.), and anhydrous sodium carbnnate (16 g.) in water (20 ml.) added. The mixture was warmed on a water bath for

about 2 hrs. and the solid which was thus produced (5.7 g.) was

collecte' and recrystallized several times, from methanol. It had

m.p. 107-108°. (Lit.", m.p. 108°).

(3-Dimethylaminopropiophenone Oxime Tlethiodide.90

p-Dimethylaminopropiophenone mime (6.8 g., 0.036 mole) was dissolved in a minimum of methanol, and methyl iodide (12 g., 0.8 mole) added. After cooling white crystals of the methiudide precipi-

tated. These were collected (9 g.), dried under vacuum and used directly in the next stage.

Phenyl Vinyl Ketoxime91.

p-Dimethylaminopropiophenone Oxime methiodide (8 g.) was added to aqueous 1M-sodium hydroxide (250 ml.), shaken and allowed to stand. The solution became pale yellow, and after 40 mins. was stored overnight in a refrigerator. Next day, it was shaken up

with ether and concentrated HC1 added to the aqueous layer until the pH was about 6. The resulting white solid was collected (3.0 g.), dried and recrystallized from pet.eter (60-80°). It had m.p. 114-5°C. 150.

Reduction of phenyl vinyl ketoxime with LiA1H 4 Attempts to reduce the oxime to the 1-phenylallyl amime by using the calculated amount of LiA1H4 at low and at room temperatures, in ether, tetrahydrofuran and in diglyme were unsuccessful.

In the latter solvent the reduction was carried out in the presence of A1C1 Starting material was recovered in all these cases. 3' When the experiments were carried out under reflux in presence of excess LiA1H (3-5 fold), the product obtained after decomposing 4 the complex with 210 Rochelle: salt solution (150 ml.) and 10.5 sodium hydroxide solution (150 ml) was not the expected allylic amine. From the n.m.r. spectrum the product appeared to be

Ph. CH —C H — CH 3 N

H

It had b.p. 85°/8 mm., m.p. 440 (Sealed tube). (Found: C, 80.95; C 81 2. H, 8.45; N, 10.00; M.Wt, 142.4. Cal. for C9H 11 N " " H, 8.33; N, 10.51; M.Wt, 133.1).

Reduction of phenyl vinyl ketoxime with zinc and acetic acid.

To a solution of phenyl vinyl ketoxime (2 g.) in glacial acetic acid (10 ml.) and water (100 ml.), zinc (5 g.) was added in small portions, then the mixture heated for 2 hrs, on steam bath.

The filtrate was diluted with aqueous sodium hydroxide then extracted 151. with ether. Unidentifiable products were obtained.

Phenylethynylcarbinyl chloride.

A solution of thionyl chloride (20.25 g., 0.17 mole) in anhydrous ether (150 ml.) was added slowly with stirring to a solution of phenylethynylcarbinol (22.5 g., 0.17 mole) in anhydrous ether (150) at 0°. The mixture was allowed to stand over-night at 0°, and was poured on to ice, after which the ether layer was separated, washed

with aqueous sodium hydrogen carbonate solution and water again, dried (Mg30 )and distilled. The chloride had b.p. 84-85°/17 mm., 4 np23 1.5514 (Lit9.9, bep. 59-60°/ 1 mm., np25 1.5508).

Attempts were made to prepare the corresponding amine from the reaction of the above chloride (3 g.) with diethylamine (1.5 g)

in cyclohexane or in chloroform (25 ml.). The mixture was kept at room temperature for about 4 hrs., but after evaporating the solvents, an unidentified mixture of products was obtained.

Phenylethynylcarbinyl chloride (3.2 g.) and hexamethylene- tetramine (2.8 g.) in chloroform (40 ml.), was refluxed for 1 hr. After evaporating the solvent, the phenylethynylcarbinylhexamine

chloride was obtained. The crude salt was degraded98 with aqueous ethanol in presence of HC1. An unidentified mixture of products was obtained. 152.

Benzylidene-ethyl amine

Ethylamine (3.6 g.) was mixed with redistilled benzaldehyde g,) with shaking and cooling in an ice-bath. The mixture was allowed to stand for 2 hrs., ether was added and the water layer

removed, the ether solution was dried (MgSO4) and distilled. It had 22 b.p. 80-810/22 mm., nn 1.5390 (Lit9.4 , b.p. 98-99°/28 mm. 2 0 1 njj .5397) .

Reaction of Benzylidene-ethylamine with ethylmagnesium bromide and with vinylmagnesium chloride.

A solution of benzylidene-ethylamine (2.6 g., 0.02 mole), in anhydrous ether (20 ml.) was added dropwise to a well stirred solution of ethylmagnesium bromide (0.04 mole.) in ether (30 ml.), Stirring was continued for several hours and the mixture allowed to stand over-night. It was hydrolysed by pouring on to ice and hydrochloric acid, the ether layer was separated and the aqueous layer extracted with ether, this ethereal solution was discarded. The bright green aqueous layer was made strongly basic with sodium hydroxide (the green colour disappeared at this point) and extracted three times with ether, the extracts dried (KOH) and distilled. The amine obtained had b.p. 90-910/15 mm., 11D19 1,4999. 11:D20 (Lit9.4 b.p. 98 -100Y 17 mm., 1.4996). 153.

When the experiment was carried out with vinylmagnesium bromide - prepared according to the method of Rosenberg et. a193 - even when the mixture of the aldimine and theGrignard reagent was refluxed for

24 hrs., separating the product as above gave only the aldimine or its hydrolysis product. 1514,

Solvents

Acetone

Analar acetone was further dried by allowing it to percolate slowly through a two foot column packed with molecular sieves. The acetone was then distilled from a small amount of powdered molecular sieves through a 20 inch column.

Chloroform

Commercial chloroform was freed from ethanol by being shaken three times with concentrated sulphuric acid. After washing with water several times and drying with calcium chloride it was distilled from molecular sieves through a

20 inch column, the first and last fractions being discarded.

The solvent was kept in a brown bottle in a refrigerator.

Cyclohexane

Cyclohexane ("Spectrosol" B.D.H.) was used without any further purification.

Chlorobenzene

This was kept over calcium chloride for two weeks and distilled from a trace of anhydrous potassium carbonate through a 20 inch column.

N:N-Dimethylformamide.

This was dried over calcium hydride for two days and 155•

decanted free of solid. Nitrogen was then bubbled through

the solvent overnight, and it was further dried by passing it

through a two foot column packed with molecular sieves,

followed by distillation. The solvent was kept over

molecular sieves.

Diglyme (diethyleneglycol dimethyl ether) Diglyme was refluxed with sodium for 6-8 hours and then distilled through a 20 inch column.

Dioxan

Dioxan was refluxed with sodium for 10-12 hours until

the metal remained bright, and then fractionated through a

20 inch column packed with Fenske-Helices, the first portion

being rejected. The solvent was kept in a brown bottle out

of contact with air.

Ethanol

Burnett's absolute alcohol was used after distillation

without any further dehydration.

pyridine and Triethylamine

These amines were dried by being boiled under reflux over barium oxide followed by distillation. The amines were stored over molecular sieves.

Tetrahydrofuran

This was purified by treatment with solid potassium 1%. hydroxide, followed by distillation from lithium altiminium hydride.

100% Sulphuric acid.

The method of preparation consists of mixing concentrated and fuming sulphuric acids in the appropriate proportions, e.g., Sulphuric acid (100 ml. 98% W/W H2SO4 -

H20, d 1.84) was mixed with fuming sulphuric acid (22.9 m1.10 — /0% W/W H2SO4 - SO3, d20 1.92). Water

Distilled water was boiled over potassium perman- ganate and redistilled, it was then de-ionized by being passed through a column packed with a mixture of cation and anion exchange resins. 157.

Salts

Lithium Salts. Commercial anhydrous lithium chloride, bromide and perchlorate were each kept for several hours at 100° under reduced pressure (0.2 mm.), before being used. The infra- red spectrum (nujol mull) of lithium perchlorate showed the presence of traces of water even after prolonged heating of the salt.

Sodium Perchlorate. Commercial anhydrous sodium perchlorate, which could be completely dehydrated by being heated under vacuum at 100°C, was used where extremely dry reaction conditions were required. Li 3601

This was prepared from the neutralization of H36C1 with the calculated amount of standard lithium hydroxide in ethanol. The solvent was evaporated on water pump and the solid then treated with 25 ml. ethanol and the solvent evaporated again. The resulting solid was dried by heating at 100.0°C (0.2 mm.) and was then dissolved in N:N-dimethyl- formamide and kept as standard solution. Quaternary salts

i) Tetraethylammonium chloride, fluoride and perchlorate were prepared as follows: 158.

Tetraethylammonium bromide (30. g.) in ethanol (100 ml)

containing water (9 ml.) was shaken for 24 hours with freshly

prepared silver oxide (1+0 g.) in ethanol (150 ml) and

filtered. The filtrate, which was shown to be free of bromide

ions,was devided to three protions, each of which was neutralised

with the appropriate halogen acid, i.e., with hydrochloric

acid, hydrofluoric acid and perchloric acid respectively.

Traces of silver being then removed by treatment of the hot

solution with hydrogen sulphide, the solvent was removed under

vacuum and the resulting moist solid (ca. 5 g.) was twice

dissolved in a mixture of chloroform and acetone (1:1) and

reprecipitated by addition of ether. It was then dried under

reducedpressure (0.2 mm.) at 70° for several hours. The

infra-red spectrum of tetraethylammonium chloride showed a

strong hydroxyl band.

ii) Tetra-n-butylammonium chloride, fluoride and

perchlorate were prepared as follows:

Tetra-n-butylammonium iodide (30 g.) prepared from

refluxing of tri-n-butylamine and butyliodide in ethanol,

was converted by mans of silver oxide and water into a

solution of the hydroxide which was neutralized with the

appropriate halogen acid, and worked up as shat for the

tetraethylammonium salts (Found, F, 7.21, Cal. for

C16H36 NF F,7.24a 159.

Silver Nitrate

Analar silver nitrate was used without any further purification.

Silver Oxide

A solution of silver nitrate (0.12 mole.) in water

(100 ml.) was treated with stirring with a solution of sodium hydroxide (0.1 mole.) in water (40 ml.). The silver oxide was collected on a Buchner funnel, washed free of nitrate with hot water, then washed several times with absolute ethanol and dried in an oven at 100.0°C. for several hours, finally being kept in a desiccator under vacuum. 160.

Kinetics

Measurements of Reaction Rates

i) Reactions of substituted 1- and 3-phenylallyl chlorides.

The reactions were folioed by observing the increase or decrease in absorption intensity of the medium at X max

2610 2570 RI 2520 R, 2530 R, 2560 R, 2570 R and 2705 5, where the substituents are p-Br, p-C1, p-F, H, m-CH p-CH3 and p-CH30- respectively. The method of Braude and GorelW o was adopted for measurements below 50.0 , and where the reaction mixture contains no additional light absorbing material. A stock solution of the chloride(10.1 ml., ca. 0.125 g/1; in(dioxan or cyclohexane) was added to 2.40 ml. of the medium contained in a 1 cm. spectroscopic cell, placed in the thermostatically controlled cell-holder of a Beckman

D.U. spectrometer. This method has the advantage that the low concentration of acid produced hat a negligible catalytic effect on the rearrangement of 1-phenylallyl solvolysis products.

Some reactions, e.g. those in N:N-dimethylformamide, or those requiring temperature in excess of 50.0°C, were carried out in long-necked reaction vessels heated in a thermostatically controlled water bath. The reaction mixture 161. was allowed to equilibrate in the flask, and a weighed quantity of the chloride contained in a short specimen tube was then dropped in. The flask was shaken vigorously, 1.0 ml samples were withdrawn immediately by means of a micro- pipette and diluted into cooled cyclohexane to stop the reaction and to give solutions of convenient absorption intensity. In reactions of cinnamyl chlorides, the first order -1 rate constants (kt min ) are calculated from:

. kt = (273--) log10 (Eo E.)/(Et - E.)

For reactions of 1-phenylallyl chlorides, the first order rate constants are calculated from:

.3 kt = (2--)F 1°g10 (E. - E0)/(E. - Et) where E is the initial, E the final and E o 00 t the observed optical density.

ii) Isomerization of substituted 1-phenylallyl p-nitrobenzoates. The rearrangements were carried out in chlorobenzen and in N:N-dimethylformamide (concentration ca. 0.015 -

0.007 mole/1.). The mixture sealed into small glass capsules, 162. was immersed in an oil bath maintained at 130.0°C, oril0.0°C

(for N:N-dimethyl formamide) by surrounding it with the vapour of boiling iso-amyl alcohol or toluene, respectively

(fig• XIV)• The reaction was followed by removing the capsules at recorded time intervals and measuring the intensity of absorption of the solution diluted with ethanol to an appropriate volume in 0.2 cm. cell at Xmax 2590 R , 2575 R 2545 a, 2565 2575 R and 2640 R where the substituents are p-Br, p-C1, p-F, H, m-Ch3, p-CH3 and p-CH30, respectively.

First order rate constants are calculated as in the reactions of the 1-phenylally1 chlorides.

iii) Measurements of polarimetric rates.

Runs in N:N-dimethylformamide and 90% aqueous dioxin were carried out with the reaction mixture contained in the polarimeter tube. The mixture (ca. 3 ml.) was prepared quickly at room temperature, at a concentration of ca.

0.17 M, and introduced by means of a narrow pi pet-Winto a

20 cm. polarimeter tube of about 2 ml. total capacity. The tube was provided with a metal outer-jacket through which water at the required temperature was circuited. After temperature equilibration (30 minutes at 40°, 10 minutes at

0C)the rotation was measured and taken as a . Further 30 o measurements were made at appropriate intervals. In between 163.

Condenser Oil bath

Iso-amylalcohol or toluene Heating mantle

Fig. XIV 164.

measurements, the tube contained in a polythene bag, was kept

immersed in the water thermostat. Rotations were measured at 5893 a on a Hilger and Watts Microptic Photoelectric polarimeter. Before each

measurement the polarimeter was set at 00, with OH polarimeter

tube filled with solvent.

First order polarimctric rates are calculated from

ka = (2.3/t) log10 (a0 /at)

a where o and at are respectively, the rotation initially and at time t (min.).

iv) Measurements of isotopic exchange rates. 36 a - The exchange of cinnamyl chloride with Li Cl

in N:N-dimethyl formamide was studied using the following

procedure:

The required volume of standard solution of Li36C1

in N:N-dimethylformamide was diluted to the appropriate volume

(35 ml.) with N:N-dimethylformamide and the reaction vessel o was immersed in a thermostat at 40.0 A weighed quantity

of the organic chloride was then introduced to give a

concentration of about 1 g / 100 ml, At various noted times a 5 ml. aliquot was withdrawn, added to pentane (35 ml.)

contained in a separating funnel and the mixture shaken well 165. then extracted with cold water (2 x 5 ml.). The aqueous extracts 36 contained Li Cl. The pentane layer which contained active organic chloride was dried over magnesium sulphate, filtered and the solvent was evaporated at room temperature on water pump, some of the organic chloride being evaporated with the solvent. The residue which contained the cinnamyl chloride, was hydrolysed completely with aqueous ethanol, then extracted with pentane. The aqueous layer containing the liberated H36C1 was analysed for hydrogen ions by titration with standard alkali and this neutral aqueous solution evaporated to dryness using an I.R. lamp. The residue which contained Na36Cl was dissolved in a certain amount of water (0.2 ml); quantities of the solution were placed in a nickel dimple planohette and the solvent evaporated by the I.R. lamp. The activity in the a Na36Cl was counted usinqlow back ground counter and corresponds to the activity of cinnamyichloride.

First order exchange rates are calculated from

kexch. m (2'3/t) 1°g10 ( (A 46,3" A t) where PLOc and -e\ t are respectively, the specifio molar activities finally and time t

Attempts were made to measure the rate of exchange of

1 -phenylallyl chloride with isotopically labelled chloride ion following the above procedure, i.e. after evaporating the pentane, 166.

the residue Which contains the two isomers was treated with ethanol in order to solvolyse the 1-phenylallyl isomer. But by measuring

the activity in the HC1 produced, no useful results could be obtained owing to the exchange between cinnamyl chloride and the acid. Attempts were made to free the solution from 01 ions (formed as HC1) which are produced during the solvolysis of 1-

phenylallyl chloride by precipitating them as the insoluble silver

chloride, by using silver nitrate, i.e, to prevent the exchange of

cinnamyl chloride with the 01- ions. But it was found that even at low temperature (-1000 and at reasonable concentrations of silver nitrate in ethanol or in isopropyl alcohol some cinnamyl chloride was solvolysed.

b - The total rate of exchange of 1- and 3- phenylallyl

chlorides with Li36C1. The following procedure was adopted: The required volume of a standard solution of Li36Cl in N:N-dimethylformamide was diluted to appropriate volume (10 ml.)

and placed in the reaction vessel which was immersed in a thermostat at 40.00C. A weighted quantity of the 1-phenylallyl chloride was then introduoed to give a concentration of about lg. /100 ml, At various noted times a 1 ml, aliquot was withdrawn and added to a

10 cm. column containing Amberlite IRA-401, a strongly basic anion exchange resin in the acetate form. The column was eluted with 167.

dry acetone. The separation of the inorganic chloride on the column

lasted about 25 min, during which time about 30 ml, of solution was collected. Separate columns were used for each aliquot. The chlorides (1- and 3- phenylallyl chlorides) in acetone were hydrolysed with water and worked up as shown in (a).

Determination of the Product Composition. The degree of solvolysis was obtained by adding a weighed

quantity (ca. 0.05 g.) of substituted 1-phenylallyl chloride to the reaction medium (25 ml.), kept at required temperature. After a certain time - determined from the kinetic run - 5 ml, samples were added to pentane (25 ml.), which was then shaken twice with water

(10 ml.); the aqueous solution was titrated with 0.01 N sodium hydroxide to Methyl Red. Weinstock has shown that recovery of hydrochloric acid from the reaction medium was better than 99$ and that cinnamyl chloride was unaffected.

For the solvolysis of substituted cinnamyl chlorides, the ratio of the concentrations of the conjugated and the unconjugated

solvolysis products (Cc and C respectively) is given by

r = C/C = (L0C0 E )/(E E 0o). 10' 0

Where and c .are respectively, the molecular extinction coefficients ( ) of pure unconjugated and conjugated solvolysis atmax 168.

products, and C is the initial molar concentration. o For the reactions of substituted 1-phenylallyl

chlorides the molar concentration of the three products

are given by:

Cc (E. + T( € cci E p ) cm.' col /( E. o

C p = T - Cc

C o C (C Cc) CC1 = CC1 p Fe where T is molar concentration of liberated acid referred to the initial concentration of substituted

phenylallyl chlorides, Co, in the spectrometric run, E CC1 is the molEular extinction coefficient of pure substituted cinnamyl chloride, and the concentration of substituted CICC1 cinnamyl chloride originally present. The total hydrolysable chloride + C (C'Ccl p0 ) was determined by keeping a sample (ca. 0.05 g) in 50% aqueous dioxan for a few hours at 30.0°C, the acid formed being titrated with standard aqueous sodium hydroxide. The values obtained were used to correct the amount of the chloride weighed out to give the initial concentration of substituted phenylallyl chlorides (Co).

The non-hydrolysable material was assumed to have E <200. 169.

Examples of Kinetic Runs.

(1) Hydrolysis of m-methylcinnamyl chloride Conc. 0.631 x 10 3 Medium 40 % Aqueous dioxan. Temp. 30.0°C.

Time (min) k (min-1) 0 0.545 1 0.475 0.314 2 0.419 0,285 3 0.375 0.297 4 0.345 0.296 5 0.322 0.297 6 0.303 0.305 7 0.292 0.300 8 0.282 0.305 9 0,275 0.308 10 0.270 0.308 11 0,268 0.292 13 0.262 0,311 0.257

Mean k = 0.301 . 1.43 170.

(2) Ethanolysis of p-Bromocinnamyl chloride

Conc, 0.611 X 10-2 g / 100 ml. Medium 96% Ethanol-Cyclohexane. Temp. 65.00C. 1 ml samples diluted to 10 ml. with cyclohexane. Absorption measured in cm. cells.

Time (min) 103 k(min 1) 0 0.610 37 0.598 1.428 52 0.596 1.150 59 0.592 1.286 77 0.588 1.252 83 0.583 1.426 143 0.573 1.166 180 0.562 1.242 206 0.552 1.350 25o 0.543 1.306 297 0.531 1,302 340 0.522 1,344 400 0.513 1,292 430 0,508 1.286 0.570

mean k = 1.298 x 10-3 = 715 171.

(3) Hydrolysis of .p-6hlor0-1-phenylally1 chloride _3 / Cone. 0.516 x 10 g./10 ml. Medium 85% Aqueous dioxan. Temp 30.0°C Eo 0.090 Solvent blank 0.010

2 -1 Time (min) E 10 k(min ) 0 0.087

3 0,108 2.065 5 0,122 2.095 7 0.134 2.050 9 0.146 2.045 13. 0.156 2,000 13 0,169 2,055 15 0,181 2,080 17 0.190 2.055

19 0.199 2,040 23 0.220 2.080 29 0.242 2.000 35 0.266 2.050 41 0,286 2,055 0.436 mean k 2.052 x 102 ROH 61.1% 172.

(4) (-)J- Ilhenylally1 chloride (polArimetric run)

Cono. 2.185 g./100 ml. Medium Nal-dimethylformamide containing LiC1 (0.222 M) Temp. 40.0°C.

OK 1) / m 1) Time 103 kpol( in 0 - 0.780 23 - 0.738 2.300 41 - 0.70o 2.650 64 - 0.670 2.355 90 - 0.630 2.365 120 - 0.586' 2.375 150 - 0.548 2.345 170 - 0.525 2.320 190 - 0.499 2.345 210 - 0,474 2.365 240 - 0.445 2.322 0.000 3 mean k = 2.374 x 10 173.

(5) (-)-1-Phenylally1 chloride (polarimetric run)

Conc. 2.285 g./100 ml. Medium 9C Aqueous dioxan containing LiC1 (0.0144 M). Temp. 30.0?C.

Time a 102 kpoi(min-1) o - 0.912 5 - 0.843 1.568 10 - 0.783 1.520 15 - 0.723 1.533 21 - 0.660 1.532 26 - 0.612 1.521 30 - 0.580 1.501 35 - 0.530 1.544 40 - 0.490 1.548 45 0.454 1.546 50 - 0.424 1.530 55 - 0.392 1.532 65 - 0.338 1.520 0,000

mean k = 1.501 x 10-2 174.

(6) Isomerization of 1-phenylallyl chloride Conc. 0,217 g./100 ml. Medium N:N-dimethylformamide Temp. 40.0°C. 0.1 ml. diluted to 10 ml, with cyclohexane Absorption measured in 0.2 mm, oells.

Time(min) 103 kn(min-1)

0 0.060 110 0.077 0.314 215 0.092 0.311 280 0,102 0.316 440 0.117 0.282 590 0.140 0.300 730 0.160 0.312 1420 0.230 0.308 1560 0.245 0.304 1690 0.260 0.310 1825 0.269 0.304 2865 0.345 0.304 3160 0,360 0.300 0.550

mean k c 0.305 x 103 175.

(7) The Exchange of Cinnamyl chloride with Li36C1 Conc. 0.822 g. /100 ml. Medium N:N-dimethyl formamide containing Li36C1 (0.163) Temp. 40.00C

Time (min) Specific Molar k (min-1) Activity exoh.

0 0 2 19.4 0,112 5 39.5 0.106 0 59.4 0,121 11 70.8 0.122 14 78.3 0.122 17 85.7 0.120 95.5

mean k a 0.116 176.

(8) The total exchange of 1- and 3- phenylallyl chloride with Li36C1

Conc, 1.0 g./100 ml,

Medium N:N-dimethyl formamide containing Li36C1 (0.1M) Temp.

-1 Time (min) Specific Molar 103 k (m ) Activity exch in 0 0 2.315

98 7.52 2.315 220 13.70 1.920

330 19.20 1.990 450 23.65 2.000 595 26.2o 1.800 1415 35.90 1.630 39.90

mean k 1.93 x 103 177.

(9) Isomerization of p-Fluoro-l-phenylaily1 p-nitrobenzoate

CpCno. 0.2536 g./100 ml. Medium N:N-dimethylformamide Temp. 110oC. 1 ml. samples diluted to 125 ml. with ethanol. Absorption measured in 0.2 mm. cells.

Time (hr.) E 103 k 0 0.415 18.75 0.448 3.09 24.40 0.467 4.99 41.90 0.515 4.74 48.48 o.535 5.08 66.08 0.566 4.86 73.21 0.576 4.2s 90.74 0.602 4.68 96.58 0.612 4.73 116.07 0.622 4.15 122.46 0.641 4.43 137.85 0.662 4.38 0.949

mean k = 4.68 x 10-3 k min_i = 0.78 x 10-4 178.

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