THE NITRATION OF THE TEREE TOLUENEAZOPHENOLS. 155 XVL-The Nitration o,f the Three Tolueneaxophenols. By JOHN THEODORE HEWITT and JAMES HENRY LINDFIELD. EXPERIMENTS which have been made on the nitration of benzeneazo- phenol with dilute nitric acid (Hewitt, Trans., 1900, 77, 49) and with the strong acid in sulphuric acid solution (Noelting, Ber., 1887, 20, 2997) lead to the conclusion that in the former case the substance reacts a6 a phenolic compound, whereas under the latter conditions its behaviour coincides with that which might be expected from a phenyl- hydrazone of quinone. More recently it has been shown that benzene- azosalicglic acid is quite analogous in its interactions with nitric acid, benzeneazo-o-nitrosalicylic acid being obtained on nitration with warm156 HEWITT AND LINDFIELD : THE NITRATION OF THE dilute nitric acid, and p-nitrobenzeneazosalicylic acid on nitration with a mixture of concentrated nitric and sulphuric acids (Hewitt and Fox, Trans., 1901, 79, 49).I n order to obtain further evidence of the generality of this reaction, the three isomeric tolueneazophenols have been nitrated with dilute acid and compared with the substances obtained by coupling toluene- diazonium salts with nitrophenol. I n each case, identical products were obtained, but as in the case of benzeneazo-o-nitrophenol, far better yields were obtained by nitrating the oxyazo-compounds than by coupling the diazotised bases with o-nitrophenol. o-5!'oZzleneaxo-o-nnitrophenoZ, CH,* C,H,*N:N*C,H3( NO,)*OK [CH, : N,: NO, : OH=2' : 1 : 3 : 41. -A.solution of 10.7 grams of o-toluidine in 30 gritrrs of concentrated hydrochloric acid and 30 grams of water mas thoroughly cooled ex- ternally with ice and salt and diazotised with 7.1 grams of sodium nitrite (97 per cent.) dissolved in 15 C.C. of water. The diazotised solution was added to 13.9 grams cjf o-nitrophenol in 100 C.C. of well- cooled methylated spirit containing 27 grams of powdered crystallised sodium acetate. The mixture was allowed to stand overnight and then the alcohol and unattacked o-nitrophenol were removed in a current of steam. The azonitrophenol was extracted from the tarry residue by ammonia, precipitated by hydrochloric acid and recrys- tallised from glacial acetic acid. The same substance was also obtained in good yield by gently warm- ing 10 grams of finely-powdered o-tolueneazophenol with a mixture of 20 C.C.of nitric acid (sp. gr. 1-36) and 60 C.C. of water. The reaction set in at about 40°, the thermometer then rapidly rising to 50'; water was added to reduce the temperature to below 40' and the mixture left for half an hour. The precipitate was collected, washed, and twice recrystallised from glacial acetic acid. The corrected melting point of the substance is 146O; a mixture of the two preparations showed no depression of melting point. 0.2560 gave 36.4 C.C. moist nitrogen at 1 5 O and 765 mm. N = 16.7. C13H,,0,N3 requires N = 16.3 per cent. The substance is very soluble in acetone or chloroform, fairly SO in acetic acid, benzene, carbon disulphide, or ethyl acetate, but only sparingly so in alcohol or light petroleum.The ace@ derivative, obtained by heating the azophenol (1 part) with fused sodium acetate (1 part) and acetic anhydride (24 parts) on the water-bath, forms golden-yellow needles after it has been recrys- tallised from acetic acid. N= 13.6. The yield was extremely small. 0.1380 gave 17.1 C.C. moist nitrogen at 26' and 754 mm. C1,H,,O,N, requires N = 14.1 per cent.THREE TOLUENEAZOPHENOLS. 157 The substance melts a t 108" and dissolves very easily in non- hydroxylic solvents with the exception of light petroleum. The benxoyl derivative, obtained by boiling the substance gently with an equal weight of benzoyl chloride for 1 hour, forms red, prismatic crystals on recrystallisation from benzene. It melted a t 1 18', soften- ing having previously taken place at about 105'.0.1300 gave 13.8 C.C. moist nitrogen at 22' and 760 mm. I n non-hydroxylic solvents, except light petrolenm, the substance dissolves easily although to a less extent than the acetate. The ethyl ether is obtained in very poor yield by the usual means. An idea of the incompleteness of the ethylation is furnished by the details of the following experiment. 0.15 gram of sodium was dis- solved in 10 c . ~ . of 98 per cent. ethyl alcohol, 1.7 gram of o-tolueneazo- o-nitrophenol was then added, and after allowing the mixture to stand for several hours to ensure complete conversion into the sodium salt, an excess (2 grams) of ethyl bromide was added. The tube was heated for 3 hours at 100-llO", and, after cooling, the contents were poured into dilute sodium hydroxide solution and the ethyl ether collected, well washed, and recrystallised from spirit.Only 0.17 gram was obtained, and the unattacked azophenol was easily recovered from the alkaline soIution by acidification.* Particular attention has been called to this resistance to alkylation, since the m- and p-tolueneazo-o-nitro- phenols give good yields of the ethyl ethers under similar conditions, N = 15.3. C,,H,,O,N, requires N = 14.7 per cent. N = 12.0. C,oH150,N, requires N = 12.06 per cent. 0.0962 gave 12.9 C.C. moist nitrogen at 21' and 764 mm. The ethyl ether forms orange needles, which melt at 83' ; it is fairly soluble in hot ethyl alcohol. m-5?oZueneaxo-o-nitrophenoZ [CH, : N, : NO, : OH = 3' : 1 : 3 : 41 was obtained by both methods, the two preparations individually and when mixed showing the same melting point.It is very necessary to have the m-tolueneazophenol in a state of purity before nitration, otherwise tarry mixtures are obtained from which the isolation of a pure sub- stance is dificult, although a fair separation may be effected by dissolving the crude preparation in hot dilute ammonia solution, allowing to cool, filtering, and precipitating the azonitrophenol from the filtrate by means of hydrochloric acid. After several recrystal- lisations, the substance separates from glacial acetic acid in nearly black, prismatic crystals melting at 12'7". By recrystallisation from light petroleum to which a little ethyl acetate has been added to increase the solubility, i t can be obtained, however, in fine, yellow * I n the particular experiment described above, 1.1 gram was thus recovered.158 HEWITT AND LINDFIELD: THE NITRATION OF THE needles melting at 128*5O. This alteration of melting point when a different solvent is used is not great, but shows that the removal of the last traces of impurity is no simple matter. 0.1926 gave 26.0 C.C.moist nitrogen at 15O and 760 mm. N = 16.0. Cl3H,,O,N, requires N = 16.3 per cent. Attempts which were made to introduce acetyl or benzoyl groups in place of the hydrogen of the phenolic hydroxyl group proved abortive, although the 0- and p-isomerides acetylate and benzoylate easily and normally. By long-continued boiling with acetic anhydride and fused sodium acetate, or with benzoyl chloride, oily products were obtained which dissolved in alkali.Even when the azophenol was boiled for 10 minutes with four times its weight of benzoyl chloride, and then allowed to stand in the cold for 3 days, it was found that the crystals which had been deposited from the solution consisted of unaltered szophenol. The great resistance to ncylation is remarkable and de- serves further attention ; perhaps future work may give some clue to the cause. Alkylation by means of sodium ethoxide and ethyl bromide is, how- ever, readily effected. The ethyl ether was prepared similarly to that of o-tolueneazo-o-nitro- phenol, and a good yield obtained ; it separates from alcohol in small, brown crystals which melt at 92'. 0.1065 gave 13-4 C.C. moist nitrogen at 17" and 764 mm.N = 14.7. C,,H,,O,N, requires N = 14.7 per cent. p-17oZueneazo.o-nitrophsnol [CH, : N, : NO, : OH = 4' : 1 : 3 : 41 is pro- duced by nitration a t about 40°, and, with care, very nearly theoretical yields may be obtained. In one case, 20 grams of ptolueneazophenol yielded 23 grams of dried, crude nitro-compound, which, after recrys- tallisation from glacial acetic acid, furnished 19 grams of substance melting at 147'. In this case, the constitution of the substacce was also settIed by comparison with a spocimen obtained by coupling benzenediazonium chloride with o-nitrophenol. The substance, which forms brown leaflets, is very soluble in benzene, chloroform, or carbon disulphide, and fairly so in acetic acid, acetone, ethyl alcohol, ether, or ethyl acetate, but almost insoluble in light petroleum.0.1360 gave 0.3035 CO, and 090640 H,O. 0.1248 ,, .17*3 C.C. moist nitrogen a t 15' and 768 mm. N= 16.4. The acetyl derivative, which was obtained in the usual way, crystal- lises from acetic acid in small, brown prisms melting at 94'. 0.1173 gave 14.0 C.C. moist nitrogen at 15' and 7'72 mm. N = 14% C = 60.2 ; H = 5.2. C,,H,,O,N, requires C = 60.6 ; H = 4.3 ; N = 16.3 per cent. C,,Hl,O4N3 requires N = 14.1 per cent.THREE TOLUENEAZOPHENOLS. 159 Benzeneazo-o-nitrophenol . . o-Tolueneazo-o-nitrophenol. p-Tolueneazo-o-nitrophenol. m-Tolueneazo-o-nitrophenol The benxoyl derivative was prepared by boiling the azophenol with three times its weightfof benzoylpchloride for 1 hour. After recrystalli- sation from a large quantity of spirit, the corrected melting point was found to be 129O.0.0829 gave 8.9 C.C. moist nitrogen at 29' and 756 mm. N = 11.6. C20H1,04N3 requires N = 12.06 per cent. The substance, which forms small, yellow plates, is easily soluble in. solvents of non-hydroxylic character, with the usual exception of light petroleum; it is fairly soluble in acetic acid, but, on the other hand, is only sparingly dissolved by alcohols. The ethyl ether was obtained by the usual method; it separated from alcohol as brownish needles melting at 1lSO.j 0.1405 gave 18.2 C.C. moist nitrogen a t 16' and 766 mm. N= 15.1. C,,HI,O,N, requires N = 14.7 per cent. Benxeneaeo-o-nityophenyl ethyl ethey was prepared for purposes of comparison by heating benzeneazo-o-nitrophenol with sodium ethoxide and ethyl bromide. After the usual purification and recrystallisation from spirit, small, brownish needles (frequently arranged in radiating groups) melting a t 93' were obtained ; the yield was good. 0,1168 gave 16.0 C.C. moist nitrogen at 24Oand 753 mm. N = 15%. Cl4HI3O3N3 requires N = 15.5 per cent. The substance dissolves sparingly in cold ethyl alcohol, fairly easily in benzene or carbon disulphide, and readily in acetone. The melting points of the substances described in this paper, and also those of the corresponding derivatives of benzeneazo-o-nitrophenol, are given in the following table : 93" 120.5" 132" ::68 "" 1 83 1 108 118 128 -5 92 1 - 129 147 1 116 - I 94 I Phenol. 1 Ethyl ether. 1 Acetate. 1 Benzoate. I-! I I EAST LONDON TECHNICAL COLLEGE.