CONSTITUTION OF BENZENEAZO-a-NAPHTHOL. 171 XVIII.-The Relatio?zship between the Orientation of Sub- stituents in und the Constitution of Benxeneaxo-a- naphthol. JOHN THEODORE HEWITT and SAMUEL JAMES MANSON AULD. THE question of the constitution of the oxyazo-compounds has areused a considerable amount of discussion, and in order to obtain further information on this point, one of the authors of the present commun- ication has, in conjunction with several of his pupils, made experi- ments on the substitution derivatives of these substances. In all cases 60 far studied, the results have given an unqualified support t o the oxyazo-formula, the phenolic nucleus always being first attacked by dilute nitric acid or bromine i n presence of an excess of sodium acetate. The appearance of a communication by Mohlau and Kegel (Ber., 1900,33, 2858), in which they ascribed a tautomeric formula to benzeneazo-a-naphthol, rendered necessary the further investigation of the action of substituting agents on the benzsneazonaphthols. The results obtained in the case of the azo-derivatives of P-naphthol are reserved for a future communication.Mohlau and Kegel found that pquinones and their derivatives172 HEWlTT generally reacted with diaminobenzhydrol) to C,H,*N(CH,),I : AND AULD: CONSTITUTION OF benzhydrol and Michler’s hydrol (tetramethyl- form compounds of the type [R=C,H, or 0 and extending the reaction to the so-called benzeneazo-a-naphthol obtained substances in which the hydrol had behaved as if the azo-com- pound were quinonoid in type.Had a strong acid been present, such a reaction would not have been surprising ; the condensation was, how- ever, carried out in the absence of such a compound. Moreover, the complicated azo-derivatives so obtained behaved, on acetylation, as quinone-hydrazones, the acetyl group attaching itself to a nitrogen atom. By the complete reduction of the acetyl derivative of benzene- azotetramethyldiaminobenzhydryl-a-naphthol, Mahlau and Kegel ob- tained acetanilide but could detect no aniline ; from these results, they concluded that benzeneazo-a-naphthol, as well as the condensation product with Michler’s hydrol, had the constitution of quinone- hydrazones. The condensation was, however, not incompatible with the presence of both forms in equilibrium in solution, whilst the course of the acetylation OF the condensation product might be explained in a similar way in conjunction with the undoubted steric hindrance which might be experienced in the case of acetylating an ortho-substituted a-naphthol.We therefore resolved to re-examine the acetylation of benzeneazo-a-naphthol, and further to study the action of substituting agents on the azo-naphthol itself. It may be mentioned here that the results of all experiments made with nitric acid on benzeneazo-a- naphthol were thoroughly unsatisfactory ; either reaction did not take place or only tarry products were obtained. Reduction of Benxeneazo-a-naphthyl Acetate. Benzeneazo-a-naphthol was prepared by Witt and Dedichen’s method (Ber., 1897, 30, 2657), and acetylated by boiling in a reflux apparatus with excess of acetic anhydride and fused sodium acetate.The melt- ing point of the product (128’) agreed with that given by Zincke and Bindewald (Ber., 1884, 17, 3030). The complete reduction of this sub- stance was effected in cold alcoholic solution, so that any possibility of one or other product becoming acetylated during the process and thus leading to erroneous conclusions might be obviated. Two grams o€ the acetyl derivative were dissolved in 100 C.C. of absolute alcohol and treated with 5 C.C. of concentrated sulphuric acid mixed with 10 C.C. of alcohol. Zinc dust was now added and the solution wellBENZENEAZO-a-N APHTH OL. 173 shaken until entirely colourless. The excess of zinc dust was re- moved by filtration and the filtrate diluted with water, rendered alka- line with sodium carbonate, and then twice extracted with ether.The ethereal extracts were united, the excess of ether evaporated, and the residue distilled in a current of steam. The presence of aniline in the distillate was confirmed by its conversion into tribromoaniline. I n one experiment, the weight of tribromoaniline obtained was prac- tically equal t o that of the benzeneazonaphthyl acetate employed. After the steam distillation, the residue in the flask was examined in order to isolate the other product of fission ; the acetoxy-a-naphthylamine could not, however, be obtained in a crystalline form. By partial reduction of benzeneazo-a-naphthyl acetate, a hydrazo- compound is obtained, which, from its insolubility in dilute alkali, evidently does not contain a free hydroxyl group.To obtain this substance, 1 gram of benzeneazo-a-naph thy1 acetate was dissolved in alcohol, a small quantity of acetic acid added, and the solution shaken with zinc dust until colourless. The filtered solution deposited crystals on standing, which were collected, washed, and dried. The substance so obtained, although a t first colourless, turned faintly yellow on dry- ing; the melting point (160-165') was far from sharp and the sub stance reddened considerably on heating. 0.1685 gave 0.4580 CO, and 0.0866 H,O. 0.1445 ,, 11.9 C.C. nitrogen" at 15O and 754 mm. N == 9.51. These results absolutely confirm the constitution usually assigned to benzeneazo-a-naphthyl acetate, namely, that it is an oxygen ester.The possibility of the existence of an isomeric derivative was also examined. Benzeneazo-a-naphthol, on treatment with mineral acids, readily furnishes salts of a-naphthaquinone phenylhydrazone. Two grams of benzeneazo-a-naphthol were added to glacial acetic acid which had been saturated with hydrogen chloride and warmed in a flask provided with a reflux tube down which 8 grams of acetyl chloride were added in small quantities a t a time. After half-an-hour's heat- ing a t looo, the product was poured into water, the precipitate collected, and recrystallised from glacial acetic acid. The acetyl derivative so obtained melted at 127' and when mixed with the acetyl derivative prepared by acetylation with acetic anhydride and fused sodium acetate did not depress its melting point.Hence salts of a-naphtha- quinone phenylhydrazone furnished derivatives of benzeneazo-a- naphthol on acetylation. C = 74.13 ; H = 5-69, C,,H,60,N, requires C = 73.97 j H = 5-48 ; N = 9.52 per cent. * Measured over 50 per cent. potassium hydroxide solution.174 HEWITT AND AULD: CONSTITUTION OF Action of Bromine on Benxeneaxo-a-naphthol. In acting with bromine on an oxyazo-compound, a solution or sus- pension of the latter in acetic acid is best employed, and it is very necessary to take especial care that hydrogen bromide is removed as quickly as it is formed. I f this be not done, the hydrogen bromide converts oxyazo-compounds into salts of quinone-hydrazones and sub- stitution takes place in the nucleus free from oxygen (Hewitt and Aston, Trans., 1900, "7, 712, 810).The bromination of benzeneazo- a-naphthol has already been effected by Margary (Gazzetta, 1884, 14, 271), who took no precautions to avoid presence of a mineral acid. The substance so prepared he regarded as pbromobenzeneazo-a- naphthol, stating that he obtained p-bromoaniline on reduction. Such a result would not have been surprising were it not that the product is described as occurring in two forms melting at 185' and 197" respectively, whereas the substance obtained synthetically by Bamber- ger melted at 237-238O (Bey., 1895, 28, 1896). Bromination, if carried out in the following manner, furnishes a product, melting a t 196O which contains no bromine in the benzene nucleus. Benzeneazo-a-naphtho1, together with its own weight of fused sodium acetate, is dissolved in 10 times its weight of glacial acetic acid.The calculated quantity of bromine, diluted with t k c e its weight of acetic acid, is then added and the mixture allowed to stand at the ordinary temperature in a closed flask until the odour of the bromine has disappeared ; this frequently requires a meek. The solid matter is then filtered off, washed with water, and recrystallised from boiling glacial acetic acid, in which the substance is fairly soluble, although the cold solvent dissolves it but sparingly. Analysis showed that a monobrorno-derivative had been produced : 0-2040 gave 0.1132 AgBr. Br = 23-97. 0-2460 ,, 0.1404 AgBr. Br = 24.22. 0-2239 ,, 17-0 C.C. nitrogen at 20° and 737 mm. N = 8.61, C1,Hl,ON,Br requires Br = 24-42 ; N = 8.58 per cent.The substance dissolves very easily in acetone, it is also dissolved by alcohol, ether, carbon disulphide, or ethyl acetate, benzene dis- solves it only sparingly, whilst in light petroleum it is almost insoluble. The solution in strong sulphuric acid has a much bluer shade than that of the parent substance. The reduction was effected by solution in alcohol and boiling with an excess of tin and hydrochloric acid in a reflux apparatus for 1 hour. After cooling, sodium hydroxide was added in excess and the mixture distilled in a current of steam. The distillate was rendered alkaline with soda, shaken with a small quantity of benzogl chloride, and theBENZENEAZO-CZ-NAPHTHOL, 175 precipitate collected and recrystallised from benzene. Colourless plates separated, which proved to be free from halogen and melted at 158' (uncorr.).The substance was therefore benzanilide. It follows that when benzeneazo-a-naphthol is brominated in presence of sodium acetate, one atom of bromine enters the naphthol nucleus. The only benzeneazobromo-a-naphthol hitherto described is the 8-bromo-4- benz- eneazo-a-naphthol prepared by Meldola and Streatfeild (Trans., 1893, 63, 1058). It is probably not identical with our compound, although its melting point, 197O, lies very near to that of the substance obtained by direct bromination. To further characterise the latter, a number of derivatives have been prepared and analysed. The ethyl ethr was obtained by dissolving, successively, 0.1 gram of sodium and 1.0 gram of the azo-compound in 6 C.C.of ethyl alcohol and heating with an excess of ethyl bromide for 2 hours at 120-130'. The precipitate obtained on addition of water was recrystallised twice from a mixture of chloroform and alcohol; the product melted at 220° (uncorr .) : 0-1060 gave 0-0540 AgBr. The ethyl ether is a black powder, fairly soluble in acetic acid and somewhat readily so in chloroform. Most of the other usual organic solvents dissolve i t only sparingly in the cold. The acetyt derivative was obtained by boiling in a reflux apparatus for 2 hours a mixture of the azophenol with 14 times its weight of fused sodium acetate and 3 times its weight of acetic anhydride, The substance was isolated in the usual manner and recrystallised from glacial acetic acid; its melting point was found to be 146O (corr.) : Br = 22-51.C18Hl,0N,Br requires Br = 22.53 per cent,. 0.1441 gave 8.55 C.C. nitrogen a t 8' and 755 mm. C,,H,,O,N,Br requires N = 7*59 per cent. To compare the product obtained by substituting bromine in benzeneazo-a-naphthol with the three bromobenzeneazo-a-naphthols, the latter were prepared and converted into acetyl derivatives. N = 7-63, The Isorne~ic Brorno6enneneazo-a-nap~t~oZs. o-Bromobenzenenzo-a-naphthoZ.-Pure o-bromoaniline (prepared from o-nitraniline by Sandmeyer's reaction and subsequent reduction of the o-brornonitrobenzene so obtained) was diazotised, the solution of the diazonium salt added to the requisite quantity of a-naphthol dissolved in methylated spirit, and an aqueous solution of sodium acetate stirred into the mixture. The product was collected, washed with dilute alcohol, and recrystallised from glacialacetic acid, in which it is fairly176 CONSTITUTION OF BENZENEAZO-a-NAPHTHOL. soluble on boiling, but only sparingly so when cold.I t melted at 183' (corr.) : 0.2917 gave 21.0 C.C. nitrogen a t 14O and 754 mm. The ucetyl derivative, after recrystallisation from boiling glacial 0.1728 gave 10.3 C.C. nitrogen at 14' and 754 mm. m-Bromo6enxemccxo-a~aphtho1, after recrystallisation from benzene, 0-2298 gave 16.8 C.C. nitrogen a t 20' and 761 mm. The acetyl derivative was prepared in the usual manner ; it melted 0.1252 gave 9.0 C.C. nitrogen at 23' and 744 mm. p-Bromo6enxeneaxo-a-naphthol has already been described by Bam- berger (Ber., 1895, ZS, 1896). The melting point given by him is 237-238O ; our preparation melted at 226' (uncorr., the corrected melting point mould be about 233').These melting points do not differ materially, but are far removed from those given by Margary, namely, 185O and 197O (Zoc. cit.). 0.0572 gave 0.0328 AgBr. The ucetyl derivative was also prepared in order to characterise the Prepared in the usual manner and recrystallised N = 8-49. C16H,,0N2Br requires N = 8.58 per cent. acetic acid, melted at 123' : N= 7-03, C,sH180,N,Br requires N = 7-59 per cent. melted a t 21 1' (uncorr.) : N = 8-36, C,,H,,0N2Br requires N = 8.58 per cent. a t 112O : N = 7.80, C,,H,,O,N,Br requires N = 7.59 per cent. On analysis : Br = 24.36. C,,H,,ON,Br requires Br = 24-42 per cent. substance further. from glacial acetic acid, it melted at 141O (corr.) : 0.1484 gave 0.3195 CO, and 0.0499 H,O. C=58*72 ; H-3.68. The substance is easily soluble in benzene or chloroform, fairly so in acetone or ethyl acetate, but only sparingly so in alcohol. It is thus conclusively proved that in absence of strong acids, benzene- azo-a-naphthol furnishes a substance which does not contain bromine in the benzene nucleus. The position of the bromine atom in the %-naphthol nucleus has not been determined ; it probably enters position 2. So far, attempts at preparing the substance by the inter- action of phenylhydrazine and Zincke and Schmidt's 2-bromo-1 : 4- naphthaquinone (Ber., 1894, 27, 2757) have been unsuccessful, although from the production of benzeneazo-a-naphthol from a-naphtha- C18H1302N2Br requires C = 58.54 ; H = 3-52 per cent.MAGNETIC ROTATION OF SOME POLYHYDRIC AT~COHOLS. 17’7 quinone and phenylhydrazine observed by Zincke and Bindewald, the carrying out of such a reaction appears easy of accomplishment. Under the circumstances, we are compelled to leave the actual proof t h a t position 2 is occupied by the bromine atom to some future occasion. EAST LONDON TECHNICAL COLLEGE.