HEWITT : PREPARATION OF BENZENEAZO-O-NITROPHENOL. 99 X. -Preparation of Benxeneazo-o-nitrophenol. By J. T. HEWITT. BENZENEAZO-O-NITROPHENOL being required for some work on which the author of the present communication is engaged, an attempt was made to prepare it in a more satisfactory manner than according to Noelting’s process, which consists in adding a solution of a phenyl- diazonium salt to an alkaline solution of o-nitrophenol (Bey., 1887, 20, 2997). Diazotisecl amines combine but slowly with o-nitro- phenol, and during the process considerable decomposition sets in, the yield being small. Direct nitration of benzeneazophenol gave p-nitro- benzeneazophenol (Noelting, Zoc. cit.), the method consisting in carrying out the nitration in a strong sulphuric acid solution. It seemed possible, however, by altering the conditions of the experiment, that substitution might take place in the phenol nucleus, and that if so, the desired o-nitro-compound would be obtained, as it was very improbable that the nitro-group should enter in the meta- position, whilst the para-position is already occupied by the azo-group, The desired result mas obtained, the necessary conditions being that the nitric acid is sufficiently dilute and the temperature carefully regulated.* * E. Tauber (Ber., 1893, 26, 1872) has described the nitration of phenolazo. benzenesulphonic acid in strong sulphuric acid, and obtained a nitro-derivative100 HEWlT'r : PREPARATION OF BENZENEAZO-0-NITROPHENOL. 10 grams of benzeneazophenol (powdered) are stirred up and thoroughly moistened with a cold mixture of 20 C.C.nitric acid of sp. gr. 1.36 and 60 C.C. mrtter. The mixture is then carefully warmed on the water-bath, the temperature being gradually raised t o about 40° (the temperature of the water-bath should not be above 45'). After about 20 minutes, a smell resembling that of o-nitrophenol is noticeable, the mass becomes thicker, and eventuiillg bubbles of gas make their appearance. At this stage, when the contents of the beaker have become a stiff paste, in which the thermometer will stand upright, they are added to an excess OC cold water, and the insoluble part collected rapidly with the aid of .a pump and well washed. After drying at looo, the weight of yellow precipitate is generally 74 grams, and the melting point about 122' (not quite sharp).Noelting gives 126' as the melting point of benzeneazo-o-nitrophenol ; after three recrystsllisations from benzene, the melting point of the above product was found to be constant at 126.5' (128.5' corrected ; the remaining melting points in this paper are all corrected for the apparent expansion of the mercury of the thermometer). The com- position of the substance was controlled by an analysis. 0.1200 gave 0.2572 GO, and 0.0390 H,O. 0*1377 ,, 21.0 C.C. moist nitrogen at 16'and 762 mm. N= 17.76. C,,H90,N, requires C = 59.21 ; H = 3.73 ; N = 17.32 per cent. If considerable quantities are desired, benzeneazophenol may be nitrated in much greater amount than 10 grams at a time, and after checking its melting point, the product can be used for most purposes without recrystallisation.As benzeneazo-o-nitrophenol could be obtained in considerable quantities, it was considered desirable t o characterise the compound more closely than had hitherto been done. The substance crystallises in small light yellow needles, gives a pale yellow powder, and forms yellow solutions in organic solvents. In strong sulphuric acid, it dissolves with a red colour, and the careful addition of water to the solution at first precipitates a red sulphate which, however, very readily gives the yellow nitrophenol on further addition of water. Whether the precipitate so obtained is a hydrate or the free azophenol, has not so far been determined. Farmer and Hantzsch state in a recent paper (Ber., 1899,32, 3098) t h a t this azophenol (or, U=58*46 ; H=3*61. with the nitro-group in the ortho-position relatively to the hydroxyl. He expressly mentions in his paper that he has chosen such a sulphonio acid derivative as otherwise the nitro-group would enter the benzene, and not the phenol, nucleus.The course of the substitution really depends on whether an azophenol reacts as such, or as a salt of a mineral acid.in their nomenclature, Nitrochinoln-PhenyZhydl.azofi) gives neither hydrate nor hydrochloride. The existence of the sulphate shows, however, that the azophenol is capable of forming salts with strong acids. Solutions of the azophenol in fixed alkalis and ammonia are of a distinct red shade, in fact, the difference of colour between the free phenol and its alkaline salts strongly recalls the relationship in colour between o-nitrophenol and its alkali salts.The sodium salt separates in red needles on concentration, and in neutral solution gives, with solutions of metallic salts, the following precipitates. Silver Nitl.de.-Light orange precipitate, practically insoluble, even in boiling water. Nagnesium Chloride. -Orange precipitate, dissolves somewhat in boiling water, and separates in groups of small needles on cooling. Zinc #ulphata.-Bright yellow precipitate, becoming crystalline on warming, slightly soluble in boiling water. Cadmium SuZ'hute.-Orange precipitate, very slightly soluble. Mercuric ChZo&de.-Yellow precipitate, appreciably soluble in boil- Calcium CIJoride.-Orange red precipitate, very slightly soluble in Strontium Chloride.-Similar precipitate to that with calcium Buvium Chloride.-Scarlet precipitate, very sparingly soluble in Lead A cetate.-Orange precipitate, insoluble.Copper 8uZphute.-Dirty orange precipitate, insoluble. Cobalt Nitrate or Nickd Chloride.-Reddish-brown precipitate. Manganese SuZphate.-Orange precipitate, somewhat soluble in Stunnous ChZovide.-Bright sulphur-yellow precipitate. I l ' e . n . 0 ~ ~ SuZphate.-Dark brown precipitate, soon turning green. Ferric ChZoride.-Bright sulphur-yellow precipitate. Aluminium SuZphute.-Bright yellow precipitate. Chrome AZum.-Yellow precipitate, not quite so clear in shade as that with aluminium. It is somewhat striking that the colours of the precipitates should vary so much. The very slight solubility of the barium salt contrasts strongly with that of the barium salts of benzeneazophenols containing the substituents in the benzene nucleus, which may be recrystallised easily from boiling water and are obtained as orange needles contain- ing 4H,O.The acetyl derivative, C,H,*N :N*C6H,(N0,)*O*CO*CH,, is easily VOL. LXXVII. I ing water. boiling water, chloride, but somewhat redder in shade. boiling water, from which it separates in very slender, long needles. boiling water.102 HEWITT : PREPARATION OF BENZ ENEAZO-0-NITROPHENOL, obtained by warming 2 parts of the azophenol, 2 parts of fused powdered sodium acetate, and 5 parts of acetic anhydride for 1 hour on the water-bath. It separates in a Bocculent state on pouring into water, and may be obtained as yellowish-brown prisms by recrystal- lisation from glacial acetic acid or benzene.It melts at 120.5O. 0.1237 gave 0-2644 CO, and 0.0428 H,O. C = 58-29 ; H = 3.85. 0.1103 ,, 14.5 C.C. moist nitrogen at 21" and 756 mm. N = 14.89. C1,HllO,N, requires C = 58-90 ; H = 3.89 ; N = 14.77 per cent. The acetyl derivative is easily soluble in acetone, ethyl acetate, or pyridine, less so in chloroform or benzene ; methylated spirit dissolves it sparingly in the cold, but fairly readily on warming, as does amyl alcohol. It is sparingly soluble in ether and insoluble in light petroleum. The benzoyl derivative,C,H,*N:N*C,H,(NO,)*O* CO* C,H,, is obtained when equal weights of the azophenol and benzoyl chloride are boiled gently for 1 hour. After pouring the product into water and leaving it until it has solidified, it is powdered, warmed with a little alcohol, and washed with repeated small quantities of cold alcohol on the pump.It separates from benzene in small, yellow crystals, melts a t 132O, is easily soluble in hot benzene, acetone, or chloroform, sparingly so i n alcohol or light petroleum, and is only dissolved in very small quantities by ether. N = 13.07. 0,1127 gave 12.4 C.C. moist nitrogen a t 13" and 764 mm. C19H,,04N, requires N = 12-72 per cent. The difference in the behaviour of benzeneazophenol on nitration, when the operation is effected with dilute acid or in concentrated sulphuric acid solution, might be explained if benzeneazophenol had the constitution, C,-H,*N:N* C,H,*OH, usually assigned to it. Phenofs undergo substitution much more readily than benzene derivatives, in which no hydroxyl or amino-groups are present, and hence nitration might be expected t o occur in the phenol nucleus.On the other hand, when nitration takes place in a sulphonic acid solution, a salt of the azophenol with a mineral acid is being nitrated, and if to these salts a formula is assigned, such as that which Hantzsch (Ber., 1899, 32, 3091) gives to the hydrochloride, the result is also easily explicable. Quinones are substituted with comparative difficulty, amines, on the contrary, with ease, an ortho- or a pars-deriva tive being produced. Hantzsch, however, assigns a similarLEAN : TETRAHYDROFURFURAN-2 : 5-DICARBOXYLIC ACID. 103 quinonoid structure to the free azophenols, and this seems to be hardly reconcilable with the experiments just described. It may be pointed out that the colour of the free azophenols much more closely corre- sponds to that of their ethers and esters, which undoubtedly possess the azo-structure, than to that of their salts with mineral acids for which the structure of quinone-hydrazone derivatives is probable, The author desires to thank Messrs. Clncher and Likiernik for help afforded in this work. EAKr LONDON TECHNICAL COLLEGE,