Ace lAARIV:- Cyelic 1nide of Sulpho be n3oit Rid ,

N-H S Znsolelolo). Naoqen attackedto carbon GropP Ohe Stae and Sulphory g the Othes Both. these houz 5Ctong. e cOithedAarn9 So the hoger attached To thenanger om js Stong acrois.k = lo 2), Le lose& hiolon NaoH looYm aSollte Salt Co NH NaoA Lso >N Na So2 So2 + Hao. Soluble Co lourless Cy sta l aeR Solid Sacchaiin M-pt - 224c. Lnsola ble in to 5q0 times as wert as ta ble Soga Soled as godiom Salt(Sacchaiin) cIhich la d soleble. Vagrain(O.o3 Gm) tablut eplaces a Obese per Son S. Lised CA SUb stilta oY Sugas Cooth inkA, Pases, moccth Cwash, Cheap

/RePARAT ION: c/loroSalp hennc acia CH3 Ho-soy cl (os) Tolvene

CH3 So2cl -toloene Sclphony to Juenr Sulhonyl Chlonde (kpei ekinndel sasi/ So D) i on c NH3 So cl G-tolere 0-tolvene Scelpkonantoe Sulphonye chloide a s knop

CooH Oxid atio So2 NH2

NaH so So/ble 1-Bsom ,5-PdyAolkdere ne

As Cmvenent B. Zor both nadicol Slstlutibn a elactioplukic Aaddli ieaclen.

ee hadieal bulstluluon allylie Cor) hen3y le ydaoga by br Cs done non-hrla Soled Ccly

aq veous soluet mu'rAure DMS and cwat acti es a Sasce olectop.hilic bromee dn Ahe oimates áo nshydiN, Ihe Cyelisten cetain Rkmatie emponds thethe aoldlion 13r, le alkenR& Cnd he 0idaln Sceondary aleehsk to hetone

paalwrn. NosH NHB -Br+HBr

Succini muele PLocliuct washed aAd eceSkallaek Acete aliol Conn pholoclad

lecorposuleou

ivd4

and dony lie Alplic ro maluen Vohl-4le NBS

Clohexene

NH

-boo Cycko Succnmde hexen C50-So) beo nunalad att Alken

pos to n elring

Aolw TKo alkoe and ecy sallced NBS Ccl. Ghe xacleèn aAkydlia tuy

initialoal h eRoruoko CM cH2 2 NBS Bule

CM- -CH C C 2 +

o mo-If butene

CH CH Ch-cuzl o Mo -bulen

Slectie boni naltion Ocug becaue ho Cnae meonale leadiis thieinduetE

en Keattuwe t encli cal la fes tnhibdos. The aly Liu bconinatun alkeR& Oceasin to adAIn the clou,Se bend. +br hsyali r t R so

Phenols

Phenols are naromatic compounds containing an--OH ring Like aloohols, they group attached the number that may be or directly o or asofugroups monohydrio polyhydric Tstem derivatives of they oontsin. Phenols are according the parent phenol are usuallyususlly named by commoncomnon (CH,0H). Examples are: OH OH

PHENOL HO-ON0, 0-CRESOL p-NITROPHENOL (2-methylphenol) (4-nitrophenol) OH OH OH O OH HO-OM CATECHOL RESORCINOL QUINOL Compounds which contain an -OH group in a side-chain attaohed to an aromatio ring are not pbenols. They are called Aromatie Alecohole. Example8 are

. CH OH OCH,CH,OH BENZYL ALCOHOL 2-PHENYLETHANOL

PHYSICAL PROPERTIES OF PHENOLS Most pure phonols are oolourlaes liquids or solids, although they are often found to1) ontain a red tint owing to the presenoe of oxidation produots. .(2)(2) Phenols have a oharaoteristio "Carbolic' odour, which in case of phenol itself is highly toxio. The are higher than aliphatic aloohols of oomparable (3) boiling points of phenols in moleoular weights. This is due to strongger intermolecular hydrogen bonding phenols relative to aloohols. bpC Compond MW 182 Phenol 94 100 162 Oyolohexanol 167 1-Hexanol 102

639 AcIDITY OF PHENOLS are but less so than Phenols muoh more aoidio than aloohols carboxylio acids or even carbonic acid. Thisis indicated in order of acidity constants: Formula K (ppror) Phenols Ar-OH 10-19 Alcohols R-OH 10-18 Carboxylie acide R-COOH 10-6 Carbonic acid HCOs 10-7 Phenols are acidio due to the formation of steble ions in For phenoxide aqueous solu tions. example, phenol itself gives phenoxide ion on dissociation. OH

+

' PHENOL PHENOxIDE ION PHENOLS8

The phenoxide ion is stable due to resonanoe

O

the Notioe that negative oharge is by effeotively dispersed. This spread throughout the ere- oharge delocalisation is a benzone ring,n On the other hand, no stabilising factor in de The regonance is possible in alkozide the pho hos. negative oharge is concentrated ions (RO*) derived o equently, alcoloohols are muoh (looalised) on a single atom. weaker acids than phenols. ozygen BFFEOTBFFEOT OF SUBSTITUENTS ON ACLDITY (1) Bffect of up Electron-Withdrawing Substituents. An electron-withdrawing group (e..NOG, -Cl, -ON, --CHO, on nb.It the -C0OA) the aromatio ring is enables ring to withdraw more eleotrons from acid-strengthen hilises the ion still the phenoxy oxygen. Tas phenoxide further and results in a mnitrophenol is more aoidio than phenol. stronger aoid. For exsmple, OH

+H0 +H

NO2 NO2 p-NIT ROPHENOL p-NITROPHENOXIDE 1ON

NO2 NO2

RESONANCTE FORMS OF p-NITROPHENOXIDE 1ON A TEXT-BOOK OF ORGANTC CHEMISTRY PEENOL, Bydrorybenaene, C,H,OE member of the series. and most important Phenol is the simplest methods Phenol is obtained by the following Preparation, Process). This involvog the Chlorobenzene (Dow and presasure followadoai (1) From Na0OH at high temperature ohlorobenzene with aqueous with dilute HCI. trestmen, ON OH Aq.NaOH 350C,150 atm

SODIUM CHLOROBENZENE PHENOL BENZENE PHENOXIDE

This prooe88 was first introduced in 1928 by the Dow Chemical Compani of U.A

air-oxidstion of oumene (la (2) From Cumene Process. This involves with dilute EC. propy. benzene) followed by treatment CH CH CH--H CH--0OH CH3CH CHa HaPO4

CUMENE CUMENE BENZENE HYDROPEROXIDE

HH0 OH+ CH,-C-CH

PHENOL ACETONE The Oumene Process acoounts for 80% of the totsl world production of phenol. The Buocess of this method is due to the &vailability ot benzene and propene from petroleum and to the formetion of acetone, a valuable by-produot. This involves fusion of sodium benzene. (3) From Sodium Benzenesulphonate. treatment with dilute HCI. Bulphonate with solid NaOH at 300°C followed by $0sH $O Na Fuming NeOH NaOH Ha$0 O fuse sODIUM BENZENE BENZENE SULPHONIC ACID BENZENESULPHONATE

ONa QH HH0 O

PHENOL This prooesa was onoe used for phenol manufaoture but is now obsolete. (4) From Benzenediazonium Salte. This reaction can be performed ea the laboratory and simply requires warming a solution of benzenediazonium chloriuc re pared from aniline, on a water bath at 50°C. PHENOLS

NO2 NH2 HNO HaSO NaNOa - HCI,OC BENZENE NITROBENZENE ANIUNE NCI OH Hao

BENZENEDIAZONIUM PHENOL CHLORIDE The phenol is recoveréd.by stesm distillation and extracted with diethyl ether (6) From Bensene (Hydroæylation). Benzene reaots with hydrogen peroxide in the prosenoe of iuorosulphonio aoid to form phenol.

OH

+ H202 HSOF

8ENZENE PHENOL

(6) From Coal Tar. Coal tar provides a natural source of phenol and oresols, bat nowadays provides less than 10% of the total supply. The middke oil fraotion (170. 9400) of coBl iar oontains phenols, oresols, and naphthalene. The oil, when oooled, depo. sits 9olid naphthalene, whioh is romoved by oontrifuging the mixture. The oil left is gitated with NaOH solation when phenol and oresols diesolve as sodium aalta.

The phenols are recovered from the above solution by passing carbon dioride through it. 20,H,ON + C0, +H,0 20,E,OH+ Na,CO% Phenol is inally isolated from the resulting mixture of phenols by fraotional distillation. Properties. (Physica). Phenol is a olourles8, hygroscopio, orystalline solid (mp 42°0; bp 182°C). The liquid form of phenol containing about 5% water is known as Crbolle Acid. Below 86:8°C phenol is only partially misoible with water but above ethanol and this temperature it is misoible in all proportions. It is readily solublo in other organio solvents. It turns pink on exposure to air and light. It has a distinotive blisters oontaot with odour, Phenol is a poison when taken orally and produoes painful in skin, The IR abeorption frequenoios of phenol are: 3610-3800 oml (0-H stretobing); 1230 om1 (C-0 stretohing); and 1400-1300 om (0-H bending). and (Ohemical). The reaotions of phenol are the resotions of the -OH group benzene ring.

REAOTIONS OF -OH GROUP reaota with sodium hydroxide or (1) Formation of Salts. Phenol is aoidic. It odinm metal to form salts. A TEXTBOO1 ORGANTC JHEMISTRY -OH + NaOH

sOD. PHENOXIDE PHENOL -OH +2Na 0-+H1 sOD. PHENOxiDE PHENOL aoids. It does not reaot with . Phenol is weaker aoid than oarboxylio oarbonate and eodium bicarbonate. sodinm -OH + Na,CO3

PHENOL -OH+ NaHCO

PHENOL (2) Reaction with FeCl Phenol gives purple colouration with one or tw to the formation of a complex. This raat drope of neutral ferrio ohloride 8olution due is given by most phenols. Fornmation of Esters. Phenol reacts with s0id chlorides (or acid anhu. dridea) in(3) aqueous alkali solution to give phenyl esters. The alkah first forms the phen. oxide ion which then reaots with the aoid ohloride. O-OH+NaOH O-ÖNa + HO PHENOL sOD. PHENOxIDE -ONa +CHc O-o--ch +Nac so0.PHENOXIDE PHENYL ACETATE

+ NaCl

PHENYL BENZOATE The rosotion of phenol with bensoyl ohloride is known as Schoten-Baumann reackion. (4) Formation of Ethers. (a) Phenol reaots with alkyl halides in alksli solution toform phenyl others. The alkali firet fornms the phenozide ion whioh then raots with the alkyl halide. CeH,OH + NaOH CoHON + H0

O-õns + CHCuCI OocH,CH, + NaCl

PHENETOLE (ETHYL PHENYL ETHER) with ()Phenolreaots dimethyl aulphate in alkali solution to form aniaole phonyl ethor). (Mothy

CHOH+ NaOH CaH,õNs* + H0

Na +(CH,)S0. OCH,+ CHHSO ANISOLE (METHYL PHENYL ETHER)

() Keacton with PCl Phonol reaots with phosphorus pentaohloride o 1o ohlorobenzene, CH,OH+ PCl C.H,CI + POCI+HC Phenol Chlorobenzene

low (6) Reaction wlth Zine Dust. When phenol is distilled with sino dust, yield of bensene is obtained.

OH +Zn ZnO+ (BENZENE)

RRACTIONS OF BENZENE RING substitution reaotions muah more readily as com- Phenol undergoes eleotrophilio in benzene oonditions used for monosubstitution benzene ring. The reaction can pared to the reaction conditions, however, we trisubstitution with phenol. By moderating is ann give that the-OH group in phenol obtain the monosubstitution product. Remember op-direotor and activator (See Chapter 34 for discussion). water (aqueous bromine) to give Ealogenation. Phenol reacts with bromine (7) the same way. preaipitate of 2,4,0-tribromophenol. Chlorine reacts in QH OH Br Br +3Bra + 3HBr

Br PHENOL 2,4,6-TRIeROMOPHENOL

o- and a mixfure of or (non-polar solvents), f the reaotion is carried in CS, CC p-bromophonol is formed. OH OH OH + Br2 O Br

O and p-BROMOPHENOL PHENOL A TRXT.B0OK OF ORGANIG CHEMteHEMISTRY with dilute nitrio aoid to give s mixture.of o (8) Nitratlon. Phenol reaote and puitrophenol. OH OH OH NONO2 +Dil. HNO (O NO o- ond p- NITROPNENOL PHENOL

ios formed. With ooneentrated nitrio acid, piorio aoid QH OH ON NO PICRIC ACio +Conc.HNO (2:4,0-TRINITROPHENOL) NO (9) Nitroatdon. Phenol reaote with nitrousaoid (obtained from NaNO,/HC 5C) to fornm p-nitroeophenol exalusively. QH OH OH NaNOa Dil. HNO HCt, 5t NO NO2 PHENOL p-NITROPHENOL

p-Nitrosophenol on oxidation with dilute nitrio aoid gives p-nitrophenol erclusively. (10) Sulphonation. When phenol is treated with oono0entrated sulphuric aoid at 20°C, o-phenolsulphonio acid is the main produot. At 100°C, p-phenolsulphonio aoid is the main product. OH C.HSO4 SO,H 20C o-PHENOLSULPHONIC ACID QH

PHENOL C.HSOs 100C p-PHENOLSULPHONIC O ACID $oH (11) Alkylation. When pbenol is warmed with an alkene or alcohol in the pre* senoe of H,S0, a mixture of o- And p-alkylphenol is formed. OH QH QH CH(CHa) +CH,CH=CH +

PHENOL CH(CHsl -and p-ISOPROPYLPHENOL PHENOLS 647 1Q Reaction. This the Reimer-Tlemann involves treai ment of phonol wth loroform in aqueouous 8odium hydroxido solution followed by aoid-hydroly Ayde is formod. If tetrachloride is u8ed in ot Balioylalde- carbon pla0e ohloroform, salioylio aoid is

formed, OH N QH CHCl CHO HH0 CHO Aq.NaOH

PHENOL SALICYLALDEHYDE

MBOHANISM. In tho abore reaotion, ohloroform first roacts with sodium bydro- dichlorocarbene. ride to produoe

C-c-CI OH, C-CL C- + C CI DICHLOROBENZENE

to form The electron-deficient dichlorocarbene then reaots with sodium phenoxide dihslide. This is then hydrolysed to form the aldehyde.

H H YCCl2 HaO fcciH

PHENOXIDE

QH OH CCIH CHO CHO o HO

SALICYLALDEHYDE other and introduces-CHO The Reimer.Tiemann reaction is also given by phenols group in the ortho position. the treatmont of sodium phenoxide with (13) Kolbe Reaction. This involves of followed by acid-hydrolysis. carbon dioxide at 125°C under 6 atmospheres pressure Salicylic aoid is formed. OH QH ONa COONa coOH 125t HtH0 CO2 atm. O +co SALICYLIC ACID SOD. SALICYLATE sOD. PHENOXIDE carbon ot adds to the electrophilie MECHANISM. The phenoxide oarbanion carbon diozide. Three steps are involved: OH OH C-OH H TEXT-B0OK Or A ORGANIC CHEMEMINTRY introd/oes other phenols and -C0OH groupi reaotion ia alao givon by Kolbe-8ohmidl reactign, The Kolbo is also oalled Thie reaotion the ortho poaition. of pheno This tho treatment ol Renctlon. involves with a ni (14) Gatterman ohloride in the preseno6 øyanide and hydrogen ilorido ture of hydrogen ia formed. Oatalyst. Salioylaldehyde OH QH OH CH=NH O CHO HCNHCI

AIC SALICYLALDEHYDE PHENOL (oHYDROXYBENZALDEHYDE)

(15) Fries Rearrangement. The phenol is first treated with acetio anhydrid., acetate. The eater i of aqueous sodium hydroxide to givophenyl in the presenoe when the group migrates from the nh hested with aluminium ohloride oatelyst aoyl of the Tho produot is a mixture of oxgen to an ortho or para position ring. dp- hydroxyaoetophenone.

OH -C-CH OH OH AlCl -CH

PHENOL PHENYL ACETATE 0 CH 0-and p-HYOROXTACE TOPHENONE

The Friee re8rrangement is also given by other phenols and introduces -COR group in the ortho and/or para positions. (16) Reaction with Benzenediazonium Chloride. Phenol oouples with bense nediazonium chloride in an alkaline solution to form p-hydroxyszobenzene (a dye)

1.NeOH 2. H BENZENEDIAZONIUM PHENOL CHLORIDE P-HYDROXYAZOBENZENE

(17) Reaction'with Phthalic dride in the Anhydride. Phenol reaots with phthalio anhy presence of sulphurio acid to form ************** * * phenolphthalein. PHENOL PHENOL HO IOr HO OH Conc. HaSo A +2H,0

PHTHALIC ANHYDRIDE PHENOLPHTHALEIN PHENOLS

(18) Reaction with 6A9 oolut of a Formaldehyde. formaldehyde, mixture of o- When phenol is and treated with an alkaline OH p-hydroxybenzyl aloohol is formed. OH OH H-C-HAq NeOH CHOH

PHENOL - and CHOH p-HYDROXYLBENZYL ALCOHOL If the reaotion is oarried at thermosetting plagtio Bakelite is high temperature and in formed. exoe8s of formaldebyde, hard (19) Oxidation. Phenol p-benzoquinone, undergoes oxidation with air or ohromio aoid to form

Cro or Oa (p-BENZOaUINONE) (20) Catalytic A Hydrogenation. Phenol on hexAnol. mixture of its vapour and catalytio hydrogen is over hydrogenation gives oyolo passed nickel catalyst at 160°C. OH +3H Ni 160 OH (CYCLOHEXANOL) Uses of Phenol. (1) About half of the total billion pounds) is used for world's of making resins produotion phenol (two is used as a phenol-formaldehyde e.g., Bakelite; starting material for: () drugs as (2) Phenol and several other dyes; (iii) such salol, aspirin; (ii) explosives e.g., pioric acid ; phenolphthalein produots of oommon use: wood preservatives, (iv) many other valuable gasoline additives ete. herbicides, nylon, antiseptios (Dettol),

COMPARISON OF PHENOL AND ETHYL ALCOHOL The six following reactions deseribe the basic differences in and ethyl aloohol: the reactivity of phenol (1) Reaction with NaOH. Phenol is more acidio to give sodium than ethyl aloohol. It reacts with phenoxide. Ethyl aloohol does not reaot with NaOH. NaO

CgHOH+ NaOH CH,ONa+H,0 CH,CHOH + NaOH -^ No Reaction (2) Catalytic Reduction. Phenol undergoes reduction with to form* Ethyl aleohol does not give this roaotion. H/Ni oyolohexanol. CaH,OH + 3H(Ni) C,H1OH (Cyolohexanol) Keaction with Diazonium Salts. Phenol reacts with benzenediazonium chloride to torm a dye. Ethyl aloohol does not form dyes. CHN,+Cl + CH,OH» C,4,N-NC,H,OH (Azo Dye) taon. actlon with FeClg. Phenol gives purple colouration with neutral ferrie ohloride solu. Ethyl alsohol does not react. A TEXT.BOOK OF ORGANIG CHEMISTRY 6.50

olcohol roucta with 0arboxvlio... Acida. "DDy Reactilon with Carboxyllc form (6) thin roaotion, Phonol do0a not give O OHa--C-0CH,CH, 4+ H.o OH,OH,OH CH-0H +

CH,OH^ Reaotion CH--0H + No with tat aloohol roaots balogen aoida to form alkyl Aclds. Ethyl Reaction with Halogen 8) reaction. doen not give this halidee Phenol HBr CH,CH,Br +Ho CH,CH,OH + Reaction CH,OH+ HBr No

PICRIC ACID, 2,4,6-Trinitrophenol direot nitration of phenol. The yield ia s It is not produced oommeroially by Picrio acid is oxidation nitrio aoid. now obta8ined to the loss of phenol by with owing with ohlorobenzene. through & synthesis that begins OH CI OH C NO2 HNO O,NYAYNO2NO2 2HNO NNeOH HaSO O H2SO O NO2 NO2 NO PICRIC ACID CHLOROBENZENE

Pioric aoid is a yellow orystalline solid, mp 122°C. It is sparingly soluble in cold water giving intensely yellow solutions. It is poisonous. Picric acid, owing to the presence of three electron-withdrawing-NO, groups, is nearly as acidie as mineral acids. Unlike other phenols, it decomposes carbonstes. Piario acid is uaed for making explosives Lyddite and Melinite. It is a valuable yellow dye for wool.

DI- AND TRIHYDRIC PHENOLS

pheaols are obtained eimilar to those used for For example,Dihydrie by methods phenol. (Catechol. It is obtaiaed by hydrolvsis of o-dichlorobenzene with dilute 8Odium hydroxide solution at 200°C and in the presonoe of copper sulphate cataly

ONa OH C NaOH ONà OH Cu24,200cC HH0 o-DICHLOROBENZENE CATECHOL (2) Resorcinol. It is obtained from m-bensonesulphonio acid. $OaH ON OH 1, NaOH 2. NaOH/ fuse SOaH m-BENZENEDISULPHONIC ACID RESORCINOL 651 PHENOLS

) Oginol (Hydroquinone). It is obtained by reduotion of p-bensoquinone tenn in thethe pre8cnoprescnce of water. p-Benzoquinone is prepsred by oxidation of aniline. iron in with NH OH K2Cr2O7/HSO4 FeHaO [O o OH ANILINE p-BENZOaUINONE QUINOL

Dihgdrio phenols aro colourless solids having melting points Catocbol 104°C; Resoroinolinol 110°d:l10* Quinol (Hydroquinone) 173°C. Their reaotions are similar to phenó1.

Trilaydric pheaols. Pyrogallol and phloroglucinol are important trihydrio phenols. acid at 220°C. () Pyrogallol. It is obtained by heating gallio OH OH HO OH HO OH

CoOH

GALLIC ACID PYROGALLOL

It is obtained from 2,4,6-trinitrotoluene (TNT). (2) Phloroglucinol. COOH CHa çOOH NO2 xMnOO,NAYNO2 FeHC HN NH2 O2N OJ NH2 NO2 NO2 TNT

HO YOH H20/H (PHLOROGLUCINOL) 100C OH or treatment of a dihydrio reaction involves the Houben-Hoesch Reaction. This zino chloride and hydrogen in the presence of phenol with an alkyl oyanide &rihydrio a phenolic ketone. ohloride. The product on hydrolysis yields

OH OH -cHN QHcH +CH,CN ZnCla oH > HCI OH

2,6-DIHYDROXY-

(INTERMEDIATE) ACETOPHENONE RESORCINOL

of aoylation pol indirect ring method for reaction provides a e Houben-Hoosch this reaotion. uno phenols. Phenol does not give OF ORGANIG OH A TEXT-BOOK CHEMISTRY 652 AROMATIC ALCOHOLS

the oontaining a hydroxyhydroxyl group/ingroup/in the compounds aloohols. side obain, aloohols the aliphatio Aromatio aro doriratiros of as aryl be reganded and may

BENZYL ALcOHOL, GH,CH,OH is isomerio with oresols. aromatio aloohol and It is the simplest obtained Benayl alcohol is Preparation. sodium bydrozide of chloride with aqueous () By hydolysis benzyl + NaOH OCHOH NaC OCH aq. BENZYL ALCOHOL BENZYL CHLORIDE

or benzoio scid. ) By reduotion of benzaldehyde

IC H 2H -OHOH

BENZYL ALCOHOL BENZALDEHYDE

LiAlH O-OH 4[ -CH,OH+H,0

BENZYL ALCOHOL BENZOIC ACID

Propertles. Benzyl aloohol is a oolourles liquid, bp 206°C. It is sparingly soluble in water.It bohsves like aliphatio primary alecohols and undergoes electrophilio sub. stitationin the benzene ring. The-CH,0H group is an o,p-direotor. However, care must be taken to avoid reaction with the hydroxyl group. Benzyl alcohol undergoes oxidation with ohromium triozide in pyridine solution to give benzaldehyde. With aoidio sodium dichromate, it forms benzoio acid.

CrOa Pyrldine CHOH BENZALDEHYOE BENZYL ALCOHOL C-OH HS0 BENZOIC ACIO Uses: Benzyl alcohol forms esters which are having fragrance of Jamine. Being a local ansesthetioused inand perfumery, antiseptic, beny it B uain ointments for relfeving itcbing.