THE NITRATION OF BENZENEAZOSALICYLIC ACID. 49 11.-The Nitration of Benzeneaxosalicy lic Acid. By J. T. HEWITT and J. J. Fox. ALTHOUGH nitro-derivatives of benzeneazosalicylic acid have already been described, the compounds have been produced by coupling a diazotised nitraniline with salicylic acid, and hence contained the nitro-group in the benzene nucleus. By this process, Meldola (Trans., 1885, 47, 666) obtained p-nitrobenzenertzosalicylic acid, and Gebek the corresponding mets-derivative (Annalen, 1888,251,188). Isomeric com- pounds containing a nitro-group in the salicylic acid residue have not hitherto been described, although from the results obtained on submit- ting benzeneazopheaol to the action of warm dilute nitric acid (Trans., 1900, 77, 99) it appeared very probable that a benzeneazo-o-nitro- salicylic acid should be formed by a similar nitration of benzeneazosali- cylic acid.As a matter of fact, benzeneazosalicylic acid furnishes VOL. LXXIX. E50 HEWITT AND FOX: THE NITRATION OP a nitro-derivative different from any of the nitrobenzeneazosalicylic acids, and the compound produced was found to be identical with a synthetical benzeneazonitrosalicylic acid, in which the nitro-group stood in the ortho-position relatively t o the hydroxyl group, On the other hand, benzeneazosalicylic acid nitrated in concentrated sulphuric acid solution furnished p-nitrobenzeneazosalicylic acid, the reaction therefore being quite analogous to that observed by Noelting (Ber., 1887, 20, 2997) in the case of benzeneazophenol. This observation furnishes an indirect proof that even the azosalicylic acids are con- verted into quinonehydrazones by strong acids, although no sa.lts with such acids have been isolated.CO,H Be~xeneaxo-o-nitrosaZ~c~Z~c Acid, C,H, =N: N-' 'OH - \-/ * NO2 Ten grams of benzeneazosalicylic acid were made into a paste with 45 C.C. of water and 20 C.C. of nitric acid (sp. gr. 1*36), and warmed gently to 65-70'. The thermometer suddenly rose to about 8 5 O , nitrous fumes were evolved, and a reddish, pasty mass resulted. This was quickly poured into water, cooled, and the flocculent precipitate collected and washed free from nitric acid with cold water. The sub- stance, after drying, was usually found t o weigh 58 to 6 grams, and to melt between 160' and 170'. After two recrystallisations from dilute alcohol, a substance melting constantly at 19'7' * was obtained. The substance separates in clusters of small, yellowish-red needles ; it is easily soluble in alcohol, acetone, or glacial acetic acid, whilst it is also fairly easily soluble in boiling water.The solubility in hydrocarbon solvents is, however, slight. On analysis, results were obtained show- ing that the substance, crystallised from dilute alcohol and air dried, contains one molecular proportion of water of crystallisation. 0.8456 lost 0.0498 on drying a t 1104 0.1100 gave 13.2 C.C. moist nitrogen at 19' and 756 mm. N= 13.72. H,O = 5.88. C,,H,O,N,,H,O requires H,O = 5-90 ; N = 13.80 per cent. The dried sub.stance was also analysed : 0.0807 gave 0,1619 CO, and 0.0225 H,O.0.1112 C = 54.72 ; H= 3-18. ,, 15.5 C.C. moist nitrogen at 23' and 746 mm. N = 15.31. In order to determine the constitution of the substance, various un- successful attempts were made to remove the carboxyl group. It was thought that prolonged heating with acetic anhydride might effect the * This melting point as well as the others given in this paper ar0 not corrected for the apparent coefficient of expansion of mercury. C,,H,O,N, requires C = 54.32 j H = 3.1 6 ; N = 14.66 per cent.BENZENEAZOSALICYLIC ACID. 51 elimination of carbon dioxide, whilst the hydroxyl group would be acetylated a t the same time. Instead of this, the carboxyl group was found to be very firmly attached, and this and the nitro-group being both in ortho-positions relatively t o the hydroxyl, protected the latter from acetylation.Heating in a reflux apparatus with benzoyl chloride led t o the production of tarry substances, from which no crystalline matter could be isolated. The process of heating the barium salt with an excess of caustic baryta was also a failure, explosion regularly occurring as soon as a temperature of 155' was reached. The substance had of necessity to be compared with a synthetical product obtained by coupling phenyldiazonium chloride with an alkaline solution of nitrosalicylic acid, [CO,H : OH : NO,= 1 : 2 : 31. The latter compound was obtained by nitration of salicylic acid in an acetic acid solution, and separated from the 1 : 2 : 5-isomeride by Hubner's method (Annulen, 1879, 195, 6), which depends on the sparing solubility of the barium salt of the 1 : 2 : 3-compound.The purity of the nitrosalicylic acid was checked by the melting point. I n coupling the nitrosalicylic acid with diazonium compounds, the same difficulty is experienced as in the case of o-nitrophenol, reaction taking place slowly and incompletely. Since the diazonium salt yields decomposition products difficult of removal, it is as well to use the nitrosalicylic acid in slight excess. The process consists in adding a well-cooled solution of phenyldiazonium chloride to an alkaline solution of nitrosalicylic acid, and allowing the interaction to proceed for three days in a cool place ; the solution is then filtered from de- posited matter and acidified. The precipitate contains the desired azo-compound mixed with a considerable excess of nitrosalicylic acid, To effect a separation, the mixed acids are dissolved in hot dilute ammonia solution and ammonium and barium chlorides added.Barium o-nitrosalicylate, although easily soluble in boiling water, is very spar- ingly-soluble in the cold, whilst the barium salt of the azo-acid dissolves very slightly even in boiling water, The precipitate obtained con- sists essentially, therefore, of barium benzeneazo-o-nitrosalicylate, and if the acid is liberated from the salt and the process of purification by means of the barium salts repeated, it is obt'ained in such a condition that when mixed with the product of direct nitration no depression of melting point is observed. I n addition to this direct proof of the constitution of the azo-acid, it may be mentioned that by reduction of an alkaline solution with hydrogen sulphide, aniline as one of the fission products may be detected with the greatest certainty by the ordinary reactions (volatility with steam, isonitrile reaction, bleaching powder test, and production of tlibromoaniline).We have been unable to isolate the E 252 HEWITT AND FOX: THE NITRATION OF diaminosalicylic acid, which must form the other fission product, on account of its ready oxidisability. Benzeneazo-o-nitrosalicylic acid dissolves in concentrated sulphuric acid with a far yellower shade than benzeneazosalicylic acid ; possibly the nitro- and carboxyl groups in the ortho-position relatively to the hydroxyl exert a sufficient attraction on the hydrogen of the hydroxyl to prevent isomerisation of the compound to the quinone- hydrazone form.This subject will, it is hoped, be further examined ; if it were found that nitration in concentrated sulphuric acid solu- tion led to the production of p-nit;robenzeneazo-o-nitrosalicylic acid, it would at least be rendered probable that isomerisation had taken place. A solution of the acid in ammonia or fixed alkalis is red in colour. The ammonium salt was found to furnish the following precipi- tates : Xilver Nitrate.-Concentrated solutions give an orange precipitate somewhat soluble in water and easily soluble in ammonia. Lead Acetate.-Yellowish-red precipitate insoluble in hot water. Mercuric Chloride.-A yellow precipitate, somewhat soluble in a large quantity of water. Stannous Chloride.-A yellow precipitate even in dilute solutions. This dissolves on warming, and does not appear to come down again on cooling, Excess of sodium hydroxide gives a deep red solution turned to a light red shade by excess of dilute hydrochloric acid.Ferrous Su&hate.-A chocolate-coloured precipitate,:turning greenish- brown on warming, The liquid becomes at the same time deep red. Ferric Cldoride.-A dark red solution and precipitate. Cobalt Nitrate.-A yellow precipitate soluble in hot water. Nickel SuZplmte.-A dirty yellow precipitate soluble in hot water. Magnesium Cl&wide.-An orange precipitate slightly soluble in hot water. Barium and Calcium ChZorides.-Orange precipitates, soluble in a large quantity of boiling water. Dyeing experiments were also made, Wool mordanted with iron gives a rich brown, with alumina a bright yellow, and with potassium dichromate, a dull yellow shade.The methyl ester was prepared from 2 grams of the acid, 10-12 grams of methyl alcohol, and 1 C.C. of sulphuric acid. The mixture was warmed in a reflux apparatus for 5 hours, poured into water aFter the greater portion of the alcohol had been distilled off, and the pre- cipitate collected, washed, and recrystallised from spirit. The substance forms small, brown needles melting at 132-134".BENZENEAZOSALICYLIC ACID. 53 0.0827 gave 0-1675 CO, and 0.0294 H,O. 0.1080 ,, 12.6 C.C. moist nitrogen a t 18' and 760 mm. N = 1.348. 0.1094 ,, 13.2 C.C. ,, 18' ,, 759 mm. N=13.92. The ethyl ester was prepared in a similar manner from the acid, sul- It forms very small, N = 12-91.C = 55-23 ; H = 3.95. $ 9 C,,H,,O,N, requires C = 55.77 ; H = 3.68 ; N = 13.96 per cent. phuric acid, and 95 per cent. ethyl alcohol. yellow needles melting at 128-129'. 0.1290 gave 14.7 C.C. moist nitrogen a t 22' and 760 mm. p-Nitrobenaeneazosalicylic cccid has already been described by Meldola (Trans., 1885, 47, 666). It may be obtained by gradually adding 2.1 grams of powdered pobassium nitrate, in small portions a t a time, to a solution of 5 grams of benzeneazosalicylic acid in 100 C.C. of concentrated sulphuric acid. Care should be taken that the tem- perature does not rise above 20' during the operation ; the mixture is then allowed to stand in the cold for 48 hours, after which it is poured into a large volume of water, collected, washed free from acid, and dried.The substance is already practically pure and the yield nearly theoretical. On recrystallisation, it was obtained as brilliant red needles. Meldola states that the melting point of the substance cannot be observed on account of blackening taking place above 225'. Our specimen, as well as one obtained from diazotised p-nitraniline and salicylic acid, did not blacken until a considerably higher tem- perature was reached, and by immersing the melting point tubes in sulphuric acid previously heated to 245--250', both specimens were observed to melt a t 253-254' (uncorr.), decomposition and blackening then taking place. The two preparations when mixed showed no de- pression of melting point. 0.1124 gave 14.7 C.C. moist nitrogen at 16' and 750 mm. N = 15.04. C,,H,O,N, requires N = 14.66 per cent. The ethyl ester of this acid was prepared from both specimens in the usual manner. Each preparation melted at 220-225', a certain amount of decomposition taking place. 0.1165 gave 14.3 C.C. moist nitrogen a t 23' and 759 mm. N = 13.82. C,,H,,O,N, requires N = 13-33 per cent. Both the m- and p-nitrobenzeneazosalicylic acids resist the action of dilute nitric acid to a greater degree than the unsubstituted acid. At- tempts at nitration, even at loo', led t o the recovery of nearly the whole of the original acids in an unchanged condition. C,,HI30,N, requires N = 13.33 per cent. On analysis : EAST LONDON TECHNICAL COLLEGE.