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FRIEDEL-CRAFTS’ REACTION APPLIED TO ISAPHTBALENE. 1141

XCVI.-The F&del- Crafts’ Reaction Applied to hTapl,,- thalene. The Action of Di-,Tri-, and Tetra- alkyl Halides. Pi*epaiwtion of apa’p’-Diszaphth- .* By ANNIEHOMER, B.A. (Fellow of Newnham College, Cambridge). A STUDY of the literature dealing with the applications of the Friedel-Crafts’ reaction to mixtures of with the di-, tri-, and tetrtlrhalogen derivatives of methane and ethane reveals the existence of many contradictory statements and of much frag- mentary data. As the development of the author’s previous work (Trans., 1907, 91, 1103) necessitated the use of this reaction, a revision and extension of much of the published work was under- taken. Whilst the typical course of the reaction is represented by the equation : RH+R’Cl=RR’+HCl . . . . . (i), it was observed that when naphthalene is used, this reaction is accompanied by others, a discrepancy which is explained by reference to the demonstration by Friedel and Crafts (Compt. rend., 1885, 100, 692) that when acts on benzene, toluene, or naphthalene alone, condensation occurs in accordance with the equation :

RH+RH=RR+H, . ._b . . . (ii). The work about to be described shows that in the condensation of an aromatic with a halogen derivative of a paraffin, reactions (i) and (ii) occur simultaneously, the difference between the reaction velocities being greatly affected by the temperature. But whilst with benzene and its homologues reaction (ii) proceeds Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. with a negligibly small velocity below 160°, with naphthalene it occurs to an appreciable extent even at 80°, and at higher temperatures becomes the main reaction. The concordant results of previous investigators have shown that the alkyl halides react with naphthalene and aluminium chloride according to equation (i), the only exception being methyl chloride, which the author of this paper has investigated. The present work is therefore confined to the condensation of the hydrocarbon with (a) as-dichloroethane, (6) methylene chloride, (c) ethylene bromide, (d) chloroform, (e) s-tetrachloro- and tetrabromo-ethane, and (f) nickel carbonyl. The condensation (e) was of special importance as promising a means of obtaining the dinaphthanthracene, C22H14, * This paper corresponds with tho two abstracts in Proc., 1910, 26, 11, 12. View Article Online

1142 HOMER : THE FRIEDEL-CRAFTS’

prepared by Hartenstein (Diss., Jena, 1892), a specimen of this substance being required for the study of its absorption spectrum in connexion with the investigation of the constitution of the tetra- methylpicene previously prepared by the author (Homer and Purvis, Trans., 1908, 93, 1319); eventually Prof. E. von Meyer kindly supplied a specimen of Hartenstein’s preparation. The condensations described in the present paper were performed in each case by treating the mixture of paraffin halogen compound and naph€halene, in theoretical proportion, with aluminium chloride not exceeding in weight 20 per cent. of the naphthalene used. Since it was soon found that rise in temperature in the initial stages favours reaction (ii) and leads to the production of PP-di- naphthyl, the condensation, whenever possible, was allowed to proceed in the cold for one or two days; the tarry product, after being heated for one and &half hours to the boiling point of the alkyl halide, while still hot was treated with hydrochloric acid and water. After half an hour the mass was extracted with benzene and the solvent separated from the extract by distillation; the residues were then fractionally distilled under (A) ordinary and (B) diminished pressure, and the fractions systematically examined as indicated below.

(a) Interaction of as-Dichloroethane and Naphthalene. From the products of this reaction, Bodroux (Bull. SOC.chim., 1901, [iii], 25, 491) isolated the a- and P-methyl- and ethyl- and f@-dinaphthyl. The violence of the reaction, which sets in immediately, has to be modified by adding the aluminium chloride gradually and by external cooling. In the present work it has been shown that-: (A) Distillation under ordinary pressure yielded three fractions : Fraction i consisted of naphthalene. Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. Fraction ii gave on redistillation a portion boiling at 243-245O. The crystals deposited from this solution on cooling yielded a picrate melting a€ 114O when crystallised from benzene, and at llOo when crystallised from alcohol, the analysis of which showed it to be the P-methylnaphthalene obtained by Bodroux. Fraction iii, which distilled at the temperature at which the glass began to soften, was obtained as a dark viscous oil, giving a crystalline deposit, which, after washing with and crystallisation from benzene, melted at 180-18Z0 ; analysis of the picrate which melted at 183O showed this substance to be B8-d;- naphthyl. It was observed that during the distillation of the products of the reaction active decomposition was taking place, a fact not noted by Bodroux. View Article Online

REACTION APPLIED TO NAPHTHALENE. 1143

(B) Distillation under diminished pressure yielded three fractions. Fraction i (below 250°/ 20 mm.) yielded on redistillation under 760 mm. pressure naphthalene and a little of an oil boiling at 240-260° ; the oil was probably a mixture of methylnaphthalenes, and was not further examined. Fraction ii (250°/20 mm.) was a highly fluorescent oil the pro- duction of which had been noted by Bodroux, who, however, did riot attempt to isolate any pure substance from it. After repeated distillation and long keeping, this oil solidified completely, and on repeated crystallisation from hot alcohol colourless, non-fluorescent needles melting at 90.5O were obtained, which agrees closely with the of dinaphthylmethane, given as 92O (Richter, Ner., 1880, 13, 1728). The fluorescent oil and the crystals had the same composition, as shown by the corresponding analyses I and I1 : I. 0.2903 gave 0.9938 CO, and 0.1635 H,O. C=93.38; H=6*31. 11. 0.1036 ,, 0.3548 CO, ,, 0.0597 H,O. C= 93.42 ;H = 6.47. M.W. by cryoscopic method in benzene=255.6 and 262.6. C,,H,, requires C = 93-97; H = 6.03 per cent. M.W. = 268. The identity of this compound with Richter’s was conclusively proved by analyses of its derivatives. On analysis of the brome derivative : 02389 gave 0.5185 CO, and 0.0763 H,O. C =59.19; H = 3.56. 0.2195 ,, 0,1922 AgBr. Br=37.27. C21H14Br2requires C = 59.15 ; H = 3-29; Br = 37.55 per cent. On analysis of the nitro-compound : 0.1505 gave 0.3083 CO, and 0.0438 H,O. C = 55.9 ; H = 3-26. 0.1455 ,, 14.92 C.C. N, (moist) at 1l0and 748.4 mm. N=12*23. C21H12(N02)4requires C = 56.2 ;H = 2.68 ;N = 12.5 per cent.

Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. The formation of PP-dinaphthylmethane (C2,H,,) rather than of dinaphthylethane, C22H18,is probably explained by Bodroux’s observation that methane and hydrogen chloride are evolved during the earlier stages of the condensation ; possibly the latter hydro- carbon is first formed and subsequently converted into methane and BB-dinaphthylmethane by the hydrogen evolved by the action of the aluminium chloride, thus: CHMe(C,,Hi), + 2H = CH, + CH,(C,,H7)2. It is scarcely probable that, as suggested by Bodroux, the fluorescent oil now shown to consist of dinaphthylmethane is a decomposition product resulting from distillation under diminished pressure; it is more probable that this hydrocarbon was not detected amongst the products of distillation under ordinary View Article Online

1144 HOMER : THE FRIEDEL-CRAFTS’

pressure because of its decomposition at the high temperature necessary for its distillation. Fraction iii (above 300°/20 mm.) was a deep red, viscous oil which deposited crystals. After purification these were obtained as a canary-yellow substance, melting at 252O, and giving an orange-coloured picrate. The quantity of this compound isolated was too small for analysis; it is possibly the s-88-dinaphthyl- ethane, Cl,H7*CH,*CH2*Cl,Hi, melting at 253*, prepared by Bamberger and Lodter (Ber., 1888, 21, 55). Thus the general result obtained is that the condensation products formed between as-dichloroethane and naphthalene, on dis- tillation under atmospheric pressure, give the methylnaphthalenes and PP-dinaphthyl, as stated by Bodroux ; whilst, on distillation under diminished pressure, dinaphthylmethane and a small pro- portion of a substance melting at 252O are obtained, but prac- tically no methylnaphthalenes or PP-dinaphthyl.

(b) Imteraction of Nethylene Cliloride aqd Nap?bthalene. Bodroux (loc. cit.) was unable to isolate substances other than a- and P-methyl- and ethyl-naphthalenes and j3P-dinaphthyl. In the present investigation the only crystalline substances obtained from the distillation of the products under diminished pressure were naphthalene and PB-dinaphthyl, the latter identified by its melting point and the properties of its picrate. The failure to isolate dinaphthylmethane, CH2(C,,€17)2, was probably due to the fact that the reaction had to be initiated at a temperature favourable to the preponderat.ing effect of reaction (ii).

(c) Interuction of Et7Lylene Bromide or Chloride and

Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. Naphthalene. Silva (Bubl. SOC.chim., 1881, [ii], 36, 24) was unable to isolate substances other than a- and P-methyl- and ethyl-naphthalenes and PP-dinaphthyl. Roux (Ann. Chim. Phys., 1887, [vi], 12, 297) obtained besides these substances a crystalline product melting at 300°, which he considered to be dinaphthylnaphthalene, Cl,H,(Cl,H7)2. Lespieau (Bull. SOC. chim., 1891, [iii], 6, 238) showed that ROUX’Shydrocarbon was identical with picene (m. p. 339O) obtained by Burg (Bey., 1880, 13, 1834) froni the distillation of lignite tar. In the present investigation it wm found that the benzene extract of the products of the reaction, on cooling, deposited crystals, which, after purification, melted above 300O. The mother View Article Online

REACTION APPLIED TO NAPHTHALENE. 1145

liquors were then subjected to distillation under diminished pressure and two fractions isolated. Fraction i (below 200°/10 mm.), on further distillation, gave small amounts of naphthalene and of an oil (230O and 280O). The latter gave a picrate melting at 139O, which is most probably the picrate of 1 : 4-dimethylnaphthalene (m. p. 139O). Fraction ii (above 250°/20 mm.) was an oil, depositing on cooling yellow crystals, which after several recrystallisations from benzene were ultimately obtained in white, glistening plates melting at 359O. The very slight solubility of the crystals, the green colour produced by concentrated sulphuric acid, and the fact that when mixed with a sample of picene kindly lent by Dr. Chattaway for spectroscopic purposes the melting point remained unchanged, showed the substance to be picene. Further, with the help of Mr. Purvis, definite proof of this identity was supplied by a study of the absorption spectra of the substance and a comparison of the results with those previously obtained in an examination of Dr. Chattaway’s picene (Homer and Purvis, Zoc. cit.). The mean oscillation frequencies of the absorption bands were :

Dr. Chattaway’s picene (N/1500-solution) ...... 2662 2740 2790 Substance under consideration (N/1500-solution) 2670 2732 2784 No trace of PP-dinaphthyl could be isolated from the products of the reaction. These results confirm the work of Lespieau in so far as the substance formed is picene and not dinaphthylnaphthalene. But whilst Lespieau had great difficulty in separating the picene from PP-dinaphthyl and methylnaphthalenes (the simultaneously-formed Lespieau’s picene melted at 339O), in the present investigation no PP-dinaphthyl was found, and in consequence the preparation of a very pure specimen of- picene was an easy matter. Hence the Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. Friedel-Crafts’ reaction with ethylene bromide can be recommended as an easy method for the preparation of pure picene. The production of picene instead of dinaphthylethane, C,,H7*CH,*CH,*C,,,H~,must; be due to a secondary reaction brought about either by a dehydrogenising effect of the aluminium chloride or by the action of heat on the dinaphthylethane first formed, thus : View Article Online

1146 HOMER : THE FRIEDEL-CRAFTS’

(d) Interaction of Cldoroform and NaphtiLalene. Schwartz (Ber., 1881, 14, 1518) did not succeed in isolating any definite compound from the tarry product of the reaction. Honig and Berger (MonalsTL., 1882, 3, 668) obtained a crystalline sub- stance melting at 189-190°, which they considered to be identical with synanthrene (m. p. 189-195O) isolated by Zeidler (Annden, 1878, 191, 298) from anthracene oil. Zeidler considered synanthrene to be identical with phosene, which had been shown by Barbier (Coiitpt. rend., 1874, 79, 121) to be a mixture of anthracene and . Honig and Berger further isolated two crystalline substances melting at 1‘75O and 215O respectively. The results obtained in the present investigation are as follows: (B) Distillation under reduced pressure yielded three main fractions. Fraction i (below 200°/20 mni.) gave on further distillation (a) naphthalene, (b) oils boiling between 220-230° and 230-240°, which were too small in amount to be further investigated, and (c) an oil which gave a portion (a) boiling between 248O and 252O and another (P) boiling between 260° and 270O. Fraction (c) (a) still contained a little naphthalene which crystallised out on keeping. After the removal of the naphthalene, the residual oil began to deposit crystals when cooled to Oo. The crystals when freed from adhering oil gave a, picrate which, when crystallised from benzene, melted at 115O, whereas when crystallised from alcohol it melted at 110O. Analyses of both specimens showed that this was the picrate of P-methylnaphthalene, which picrate is stated to melt at 115O. The oily filtrate, which remained liquid after being kept for some time in a freezing mixture, was proved by the analysis of its picrate (m. p. from alcohol 108O, Bodrous gives 116O) to consist of a-methylnaphthalene. Fraction (c) (P) (between 260° and 270O) contained a-ethyl- naphthalene, as shown by analysis of the picrate, which melted at Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. 98-99O, a temperature identical with that given by Bodroux. Fractions (ii) and (iii) were separately examined for the sub- stance (m. p. 189-190°) obtained by Honig and Berger. The distillates were extracted with light petroleum, alcohol, and benzene; but all these extracts yielded the same substance, which was recognised by its melting point and other properties as PP-dinaphthyl. Determinations of the carbon and hydrogen are inadequate to corroborate this result and to supply conclusive proof that the main product of the reaction is BP-dinaphthyl (C2-,HI4), and not synanthrene (C14Hlo), as stated by Honig and Berger : CZoH14 requires C =94.49 ; H = 5-51 per cent. M.W. = 254. C,,H,, ,, C=94*38; H=5*62 ,, M.W. = 178. View Article Online

REACTION AI'PLlED TO NAPHTHALENE. 1147

Honig and Berger, using Dumas's method, did not succeed in obtaining a trustworthy value for the molecular weight of their substance because of the decomposition occurring at the high temperature needed for volatilisation. The slight solubility of the substance makes the application of the cryoscopic methods of doubt- ful value; but the required proof is furnished by an analysis of a derivative such as the picrate (m. p. 182O): 0.2160 gave 22.42 C.C. N, (moist) at 19O and 751.8 mm. N= 12.26. 0.1878 ,, 19.96 C.C. N, ,, ,, 19O ,, 751.8 mm. N-12.34. C,,H,,,(C,H30,N,), requires N = 11.79 per cent.

C14H10'(C6H30jN3) 97 = 97 These figures prove conclusively that the compound isolated by Honig and Berger, which they supposed to be identical with synanthrene, CI4HIO,was really PB-dinaphthyl, Cz"H14. (A) Distillation under the ordinary pressure yielded products which, when carefully fractionated, gave methylnaphthalenes and PP-dinaphthyl as under (B), and besides these a small amount of a crystalline substance melting at 210°, and probably identical with Honig and Berger's fraction melting at 215O. The presence of this substance (m. p. 215O) would account for the fact that Honig and Berger obtained a less pure sample of PP-dinaphthyl than that obtained from the distillation under diminished pressure, in which no such fraction of higher melting point was present. Thus the general result obtained shows that reactions (i) and (ii) occur simultaneously (p. 1141), and that whichever is the mode of separation and isolation, the products of the reaction are the same. The reaction proceeds so vigorously as to lead to con- siderable rise in temperature, which accounts (1) for the pre- ponderating amount of PP-dinaphthyl formed, (2) for the absence of trinaphthylmethane, CH(C,,H,)3, the primary product of the reaction, which by secondary reactions with the aluminium salt had Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. been converted into the methyl- and ethyl-naphthalenes actually isolated. Friedel and Crafts have demonstrated the decomposing effect of aluminium chloride on complex such as triphenylmethane at temperatures as low as 75O (Trans., 1882, 41, 115). Moreover, these results would lead one to expect that the action of carbon tetrachloride which has not been investigated is not likely to lead to the synthesis of tetranaphthylmethane. View Article Online

1148 HOMER : THE FRIEDEL-CRAFTS’

(e) Interaction of ALLyl Tetrahalides and Naphthalene, and (f) Interaction of Nickel Carbon91 and Naphthalene. Lespieau (Zoc. cit.) and Hartenstein (Zoc. cit.) both tried to pre- pare a dinaphthanthracene by the action of s-tetrabromoethane on naphthalene, using the proportions required for the equation :

but in both cases the only crystalline product obtained was BB-dinaphthyl. Bartenstein, however, succeeded in preparing a dinaphthanthracene by the following method : Concentrated sulphuric acid acting on 1 : 4-dihydroxynaphthalene-2-carboxylic acid produced by a process of oxidation and dehydration, followed by condensation, a quinone, C,,H,,O,, which on distillation with zinc dust gave a hydrocarbon, CZ2,Hl4,isomeric with picene (com- pare Trans., 1908, 93, 1319, where full details are given). Dewar and Jones (Trans., 1904, 85, 212) had shown that nickel carbonyl, acting on hydrocarbons of the benzene series in presence of aluminium chloride, yields an aldehyde, which is sub- sequently reduced and condensed to an anthracene derivative, thus :

But when extending their investigations to naphthalene, they obtained as the main product of the reaction a crystalline sub- stance, subsequently identified as PP-dinaphthyl (Homer, Zoc. cit.). In addition to the PP-dinaphthyl, they also isolated a small amount (0.03 gram) of an orange-coloured, crystalline substance, melting at 265O, which, however, they did not investigate. The results obtained in the present investigation on the inter-

Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. action of s-tetrabromo- or tetrachloreethane and naphthalene showed that the products of the reaction on distillation under reduced pressure yielded three fractions. Fraction i (below 200°/20 mm.) and Fraction ii (between 200° and 280°/20 mm.) were not further investigated. Fraction iii (above 300°/20 mm.) was a dark oil, which on cooling partly solidified to a, mass of deep-coloured crystah The crystals were repeatedly washed with light petroleum and cold benzene to free from adhering oil; they were then extracted with boiling alcohol to remove any PP-dinaphthyl, and finally repeatedly crystallised from benzene, until a substance melting constantly at 267.5O wi~s obtained. The serious difficulty encountered in the investigation of this substance was due to the extremely small amount available; although evidently formed in considerable quantity during the View Article Online

REACTION APPLIED TO NAPHTHALENE. 1149

reaction, the separation from the portions which could not be distilled was very cumbersome. Fractional extraction with xylene and other solvents was tried, but did not prove satisfactory. Distillation from a glass retort under the ordinary pressure yielded no better result as the substance was accompanied by a dark red, viscous oily product, which made the purification of the former a matter of great difficulty. The substance thus obtained was insoluble in ether, alcohol, glacial , or light petroleum; very sparingly soluble in cold benzene or xylene, hot alcohol, or hot glacial acetic acid; sparingly so in hot benzene, xylene, or ethylene bromide. When first prepared, it crystallised in lustrous plates of a deep orange colour, which persisted even after boiling the solutions with animal charcoal for several hours, or after distilling with animal charcoal, or after ten crystallisations from benzene and ethylene bromide. The purified substance readily sublimed in lustrous, orange plates, and gave fluorescent solutions. With concentrated sulphuric acid at the ordinary temperature it gave a colour similar to that of an aqueous solution of permanganate, and the liquid thus obtained, when considerably diluted, showed bands in the green region of the spectrum from ~=5500to h 5425 (approx.) and from A 5300 to A 5200, whilst solutions twice as strong showed only one band, namely, A5600 to ~5200.The addition of a drop of nitric acid to the sulphuric acid solution changed the colour to magenta ; the magenta-coloured solution showed two bands at approximately ~5300to ~5200and A4975 to h4825, and in stronger solution only one band at x 5595 to h 4670. On analysis of the orange crystals (m. p. 267'5O): 0.1650 gave 0.5703 CO, and 0.0812 H,O. C= 94.26 ; H =5*40. 0.0997 ,, 0.3470 CO, ,, 0.0465 H20. C=94.9; Hz5.23. Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. C2,H,, requires C = 94.96 ; H = 5-04 per cent. As it is generally accepted that very close concordance cannot be obtained in analyses of hydrocarbons containing so high a percentage of carbon, and as the above results are, within the limits of experimental error, in good enough agreement with CZ2Hl4, the formula of the substance I had set out to prepare, it did not seem necessary to carry out further analyses at the cost of further quantities of the small amount of material at my disposal. The very slight solubility of the hydrocarbon made it impossible to determine the molecular weight by cryoscopic methods. Of two determinations by Victor Meyer's vapour density method, using a lead bath, the one had to be discarded as worthless owing to decomposition of the substance; the other, carried out at a lower View Article Online

1150 HOMER : TEE FRIEDEL-CRAFTS'

temperature, gave the value 282 (C,,HI4 requires 278), which was considered as probably trustworthy, since inspection of the tube showed that there had been only very slight decomposition, and, as a matter of fact, the crystals were recovered and used again. Analogy to anthracene would lead one to expect that if this hydrocarbon is an anthracene derivative, it would, on reduction with phosphorus and hydriodic acid, yield a hydride with the elimination of an anthracene cross-linking, and that this substance, as is t.he case with anthracene hydride, would be more soluble than the parent substance. If so, then the determination of the mo'lecular weight of the hydride by cryoscopic methods would afford a check on the molecular weight of the parent substance, the value of which rests on the evidence of only one determination. The interaction of red phosphorus and hydriodic acid (D 1.7) with the hydrocarbon in sealed tubes at 250° gave a white, crystalline product, very soluble in acetone and benzene, and slightly soluble in alcohol, the white crystals melting constantly at 178*5O. On warming with sulphuric acid, the crystals gave a rose-pink colour, which in concentrated solution showed a band at (approxi- mately) h=5800-5420; addition of a drop of nitric acid to the sulphuric acid solution changed the colour to a beautiful red, which on warming gradually became rose-pink, and finally yellow. Treatment with picric acid in benzene solution gave an orange picrate. On analysis of the hydride: 0*0810gave 0.2743 CO, and 0.0550 H,O. C = 92.36 ; H = 7.54. C,,H,, requires C = 92-96; H = 7-04 per cent. M.W. = 284. C2,H,, ,, C = 92.39 ; H = 7.69 ,, M.W. = 286. For compounds containing such a high percentage of carbon, the results of analyses alone cannot be relied on for furnishing sufficient evidence of deciding whether the hexa- or octa-hydride has been formed, although the results for the carbon and hydrogen Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. are very near those required for the formula C22H22. However, the question as to which hydride has been formed does not materially affect the present investigation. An attempt to deter- mine the vapour density of the hydride by Meyer's method (using s lead bath) failed owing to the decomposition of the substance. Molecular-weight determinations by the cryoscopic method, using benzene as solvent, gave 270 and 282, values which afford the required check for the molecular weight of the parent substance. They show t.hat in the determination of the latter by a vapour density method, at the temperature of the experiment there had been no dissociation and no appreciable decomposition, and hence that the one value, namely, 282, can be regarded as trustworthy. A picrate of the parent hydrocarbon was prepared. It con- View Article Online

REACTION APPLIED TO NAPHTHALENE. 1151

sisted of chocolate-coloured needles, and on recrystallisation from benzene melted constantly at 223-224O. Treat'ment of the hydro- carbon suspended in glacial acetic acid with chromic anhydride yielded an orange-yellow quinone sparingly soluble in boiling alcohol or benzene, and readily so in glacial acetic acid or pyridine; when purified by sublimation it melted at 335'. The author next examined the crystals (m. p. 265O) obtained by Dewar and Jones froin the nickel carbonyl reaction (p. 1148), and found that in appearance, colour, and solubility they were identical with the crystalline substance obtained in the inter- action of tetrabromoethane and naphthalene just described. The identity of the two substances was conclusively proved by the following tests. 1. They both gave the same colour with concentrated sulphuric acid, the liquids exhibiting the same absorption bands. 2. In the mixed melting-point test no depression of the melting point took place. 3. The picrate of Dewar and Jones' compound was prepared; it consisted of chocolate-coloured needles (m. p. 223-224O), which did not lower t6:e melting point (223-224O) of the picrate of tho hydrocarbon C2,HI4. It is thus evident that the five-ring compound which Dewar and Jones expected to obtain had, as a matter of fact, been formed, and was the orange-coloured, crystalline hydrocarbon which they had not investigated. The synthesis wits repeated, using the aluminium salt and the naphthalene in the proportion of 1 : 5 instead of 1 : 1, as done by Dewar and Jones. No trace of naphthaldehyde could be found in the products of the reaction, whether allowed to proceed at the ordinary temperature or at looo. From the crystalline product of the reaction there was obtained, besides B/3-dinaphthyl, which formed the bulk, a small amount of the crystalline hydro- Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. carbon, melting at 267'5O. Although the distillation of the tarry residues was easy to control, yet the presence of so much PP-di- naphthyl rendered the purification of the other substance so difficult a matter that the relative yield was not so good as that obtained under (e) when no PP-dinaphthyl was formed. The absence of naphthaldehyde in the products may be due to the fact that even at the ordinary temperature the aldehyde is acted on by the aluminium chloride as fast as it is formed. In order to test this hypot%esis, an attempt was made to prepare naphthaldehyde by the Gatterman-Koch synthesis, but without success. It is thus evident that under the conditions of Dewar and Jones' experiment, naphthaldehyde cannot be obtained, and that nickel carbonyl acting on naphthalene yields besides PB-di- View Article Online

1152 HOMER : THE FRIEDEL-CRAFTS’

naphthyl, a small amount of a substance which can also be obtained by the Friedel-Crafts’ synthesis vith naphthalene and tetra-bromo- or -chloro-ethane. The constitution of this hydrocarbon, melting at 267’5O, and obtained by the above two independent methcds, is that of di- naphthanthracene, CZ2Hl4,for the following reasons : I. (i) The formation of the substance by two distinct synthetical reactions, each of which in the benzene series yields anthracene derivatives, namely, (a) by Dewar and Jones’ reaction, and (6) by the Friedel-Crafts’ reaction with tetra-bromo- or -chloro-ethane, provides evidence of the strongest possible nature that the substance is a dinaphthanthracene compound. (ii) The comparative study of the absorption spectra of the hydro- carbon under consideration, of its hydride, and of Hartenstein’s compound, carried out in conjunction with Mr. Purvis, has shown that Hartenstein’s compound and the C,,H,, under consideration are isomeric dinaphthanthracenes. 11. The results of analyses (p. 1149) are in sufficiently good agree- ment with those required for C22H14, the preparation of which had been the main object of the research. 111. For a compound C22H14, the following structural formulae are possible, if the formation of symmetrical six-carbon ring products only is assumed: /\/\/\/\ \ IIII1 fr \/\/\I/\/\/ A. BBB’p’-Dinaphthanthracene. C. aBa’B’-Dinaphthnnthracene. Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. B. /3B/3’/3’-Dinaphthophenanthrene. D. Picene. of which, on the ground of the synthetical evidence given under I, A and C only need be considered; moreover, the melting point of the hydrocarbon, of its picrate, and of its quinone, toge-ther with the purple colour given with concentrated sulphuric acid, exclude the possibility of the formula D, which is that of picene. It remains therefore to decide between the formulz A and C, and the evidence available clearly points to C. (a) It has been previously stated that Hartenstein had prepared a dinaphthanthracene by the reduction of a quinone, C2,H1006,with zinc dust. A comparison of the properties of the dinaph- thanthracene compound synthesised from naphthalene and tetra- View Article Online

REACTION APPLIED TO NAPHTHALENE. 1153

chloroethane w'ith those of Hartenstein's compound (C22H14)shows that the substances are different: Compound synthesised from naphthalene and Hartenstein's compound. s-te trachloroethane. Melting point ...... About 260", not sharp. 267*5",sharp. Appearance and colour. White, lustrous plates, Yellow, lustrous plates, which readily sublime. which readily sublime. Colour with strong sul- On warming, blue. In the cold, purple. phuric acid. Strong solution shows Strong solution shows an ill-defined band, one band, A 5800-A 5600. A 5600-A 5200. Dilute solution shows Dilute solution shows very indistinct band. two bands, A 5500-A 5425. A 5300-A 5200. Quinone ...... M. p. 205-206". M. p. 335". Picrate ...... Chocolate-coloured nee- dles, m. p. 223-2243 The method of formation of Hartenstein's compound practically fixes the constitution as that of A, namely, /38/3'8'-dinaphthanthra- cene, since it is difficult to see how the condensation of 1: 4-di- hydroxynaphthalene-2-carboxylicacid could have taken place in any other way. The dinaphthanthracene (m. p. 267.5O) must therefore be the u&c'B'-derivative. Conclusive direct evidence might have been obtained from the potash fusion of the quinone (m. p. 335O), which should have yielded u- and p-naphthoic acids, but unfor- tunately this could not be accomplished on account of the small amount of substance available. jb) Further indirect confirmatory evidence is, however, furnished by a study of the other Friedel-Crafts' syntheses involving the use of naphthalene, which shows that in the cases where the reaction proceeds according to equation (i) (p. 1141) there is no pre-

Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. ferential formation of a-derivatives at the expense of the p or vice versa; in the case of the action of dihalide alkyl derivatives on naphthalene, the substances isolated are either a- or /3-mono- substitution products, or in cases where two hydrogens of the naphthalene molecules are eliminated, the compounds contain both a- and 8-linkings, as is shown by the formation of picene from ethylene bromide. Summary. I. In Friedel-Crafts' syntheses with naphthalene and alkyl halides there is a simultaneous occurrence of two reactions : RH+RCl=RR+HCI ...... (1) RH+RH=RR+ZH ...... (2). In order that (1) may become effective, it is essential that (a) VOL. XCVII. 4G View Article Online

1154 FRIEDEL-CRAFTS’ REACTION APPLIED TO NAPHTHALENE.

the initial stage of the reaction should be allowed to proceed at the ordinary temperature, (6) the distillation of the products of the reaction should be carried out under diminished pressure. 11. (i) The action of as-dichloroethane under the above conditions yields P-dinaphthylmethane, formed as the result of a secondary reaction from dinaphthylethane. (ii) In the case of methylene chloride, when it was not possible to work under these conditions, the only product was PP-dinaphthyl. (iii) The action of ethylene bromide yields picene as the result of a secondary action, namely, the decomposition of the s-di- naphthylethane, C,H,(C,,H,),. (iv) The action of chloroform does not yield synanthrene, as stated by Honig and Berger, but PB-dinaphthyl and monoalkyl- naphthalenes, due to a secondary reaction between aluminium chloride and trinaphthylmethane. (v) The conditions have been described for the easy preparation of pure picene by means of the Friedel-Crafts’ synthesis with ethylene bromide. 111. (i) From the products of the action of tetra-bromo- or chloro-ethane on naphthalene in presence of aluminium chloride there has been isolated a, hydrocarbon, C2,Hl, (m. p. 267.5O), which on reduction gives a, hydro-derivative melting at 178-5O. (ii) The same hydrocarbon (m. p. 267.5O) has been isolated from the products of the action of nickel carbonyl on naphthalene in presence of aluminium chloride (Dewar and Jones’ reaction), (iii) The hydrocarbon isolated according to (i) and (ii) is not the same it9 Hartenstein’s compound, C,,H1, (m. p. 235-260O). (iv) Tlie chemical evidence supports the view that whilst Hartenstein’s compound is a PBB’ PI-derivative, the hydrocarbon melting at 267.5O is an aPa’PI-dinaphthanthracene.

Published on 01 January 1910. Downloaded by Middle East Technical University (Orta Dogu Teknik U) 12/02/2016 20:08:00. In conclusion, the author wishes to thank Mr. H. 0. Jones, M.A., of Clare College, Cambridge, for the keen interest taken in the progress of the work described in this paper. The expenses of the research were in part defrayed by a grant from the Research Fund of the Chemical Society.

UNIVERSITY CHEMICAL IAABORATORP, CAMBRIDUE.