of heat, the speedy browning of the liquid showed that a more vital action had taken place. The best results with this method were obtained by long boiling of the dinitrodibrombenzol with an aqueous solution of potassa. Owing, however, to the slight solubility of the nitro-compound in water, but a small amount of the phenol salt was formed. I then endeavored to utilize a reaction which I described, some time ago,* as taking place between dinitromonobrombenzol and potassium nitrite, when the two substances are heated under pressure in presence of dilute alcohol. The formation of dinitrophenol takes place easily: C ̧H ̧(NO,),Br+2KNO,=C,H,(NO,),OK+KBr+N,O,(?) The resulting oxide or oxides of nitrogen have here the beneficial effect of exerting an oxidizing action. The great objection to the use of an alkali in forming hydroxyl derivatives from nitro-halides, is the tendency it has to affect the nitrogroups converting them into azoxy-compounds. By the use of potassium nitrite all reducing action is avoided-in fact, prevented-by the presence of the nitrogen oxide. The oxides react also on the alcohol present, forming aldehyde. Some of the B-dinitroparadibrombenzol was dissolved in dilute alcohol, and an equal weight of KNO, added. On standing, the KNO, extracts the water from the dilute alcohol, forming an aqueous layer on which the alcoholic solution rests. By standing, even without warming, the line of contact between these layers solidifies to a crust of red needles. On boiling, however, the action is soon complete, and every trace of the B-isomer is converted into the phenol. The reaction is precisely analogous to the former : CH,(NO,),Br,+2KONO=C,H,(NO,),BrOK+KBr+N,O,(?) Some of the pure a was then treated in a similar manner, but did not suffer the slightest change. Some samples of KNO2 gave a slight coloration, but this was owing to the presence of free potassium hydrate. They gave no reaction after the potassium nitrite had been moistened with a few drops of dilute nitric acid. The oil that I take to be a gamma-isomer, also remained unaffected. This method enables me to overcome several hitherto almost insurmountable obstacles. The separation and purification of the beta from the alpha by crystallization is extremely difficult, and from the gamma almost impossible. By direct treatment with KNO,, of the mass obtained by nitrition of the dibrombenzol however, all the beta isomer can be extracted in the form of phenol salt, leaving only the alpha, a solid substance * This Journal, August, 1876. fusing at 159°, and the gamma, an oil, which I hope will prove easy of separation. It also forms an excellent test of the purity of the alpha-compound, since the color of the potassium beta-phenylate is so vivid, that if the alpha contains the slightest trace of the beta, it is shown by the formation of a red tint on boiling it with dilute alcohol and potassium nitrite. By treating the beta-compound in the same manner, evaporating to dryness and extracting with hot carbon disulphide, an admixture of the alpha and gamma modifications is easily revealed. In this manner, I have succeeded in proving that several specimens of what I thought to be pure alpha and beta, were not absolutely free from isomers, although the fusing points had long since ceased to show any appreciable variation. Finally this method promises a means of obtaining phenols by substitution of the halide in those nitro-halides which on treatment with an alkali suffer substitution of the nitro-group.* For if a reaction takes place it is only the halide which can be affected. Preparation.-150 grams of the raw product, obtained by nitrition of the paradibrombenzol, were treated in a flask with boiling absolute alcohol until all was in solution. The boiling liquid was diluted with hot water until the substance began to permanently separate. Alcohol was then added until solution had taken place, on which water was again added, the liquid being kept boiling all the time. In this manner, by successively adding water and alcohol, the volume of the liquid was brought up to about 1 liters. The object of this excessive dilution was to prevent the separation of the liquid into two layers from the removal of the water by the KNO2 The flask was taken off the sand bath, and 100 grms. of KNO, carefully added. It was then replaced, and the liquid allowed to boil violently. The formation of the phenol salt took place quickly. In about half an hour, during which water was occasionally added to replace the loss by evaporation, the reaction was completed. The contents of the flask were poured into a tall beaker holding about 1 liters of cold water, stirred, allowed to settle, and washed several times by decantation to remove the potassium bromide and unchanged potassium nitrite. The mass was brought on a filter and allowed to drain, after which it was. placed in a dish and heated in a water bath till all moisture was driven off. By repeated warming with carbon disulphide, all traces of the unchanged isomers were easily removed. The red salt was then purified by crystallization from dilute alcohol, dissolved in boiling water and carefully decolorized with di *As for instance the dinitro-chlorbenzol of Laubenheimer, Ber. d. d. chem. Ges., viii, 1929; ix, 768. lute* hydrochloric acid (1: 10), filtered, washed and purified by crystallization from dilute alcohol.† Analysis.-A combustion gave: 0-2852 grms. of substance yielded 0.2870 grms. of CO, and 0.0422 grms. of H2O. Properties.-This compound is identical with the dinitrobromphenol obtained by Körnert from nitrition of bromphenol. It forms when crystallized from water or alcohol, long, flat, very thin and strongly glittering needles, fusing at 71°. Körner found 78°. On careful heating it volatilizes unchanged. Exposed to the air it soon turns reddish, undoubtedly, as Körner suggested, from the presence of ammonia. Heated under water, it fuses to a yellow oil. It has strong tinctorial powers, dying the skin yellow. In all these properties my observations agree entirely with those of Körner. By heating with concentrated sulphuric acid, decomposition sets in, and a gas is liberated which smells like nitrous acid, while a (sulpho?) acid giving a barium-salt soluble in water, is obtained. When heated on a platinum foil, it burns brightly with a luminous yellow, smoky flame. Thrown on a red-hot platinum foil it puffs. On heating the phenol with fuming nitric acid a violent action took place. The resulting liquid on evaporation furnish an abundant quantity of picric acid. There are already several instances known where picric acid is formed by the substitution of a halide by the nitro-group. A directly analogous case is quoted by Post+ who mentions. that picric acid is formed by nitrition of the phenol isomeric to this (dinitrobromphenol fusing at 117°). This proves conclusively then, that, when a halide is expelled by direct treatment with nitric acid, we are not in a condition to assume that the entering nitro-group takes the same relative position as the antecedent halide; for, as in the case above shown, both the dinitrobromphenols give picric acid on nitrition. * In many cases the addition of concentrated hydrochloric acid to a hot, concentrated solution of a nitro-phenol salt, will entirely decompose the phenol. If I am not mistaken, this fact has already been noticed, but I cannot recall the reference. This compound is also formed when ẞ-dinitroparabromaniline is heated with a solution of potassium hydrate. Ber. d. d. Chem. Ges., vii, 334. Armstrong, Ber. d. d. Chem. Ges., vi, 649. AM. JOUR. SCI.-THIRD SERIES, VOL. XVI, No. 91.-JULY, 1878. It is not a little peculiar that nitric acid should drive the bromine atom out of dinitrobromphenol, forming picric acid; for picric acid when treated with bromine, yields* dinitrobromphenol. Solubility. Difficultly soluble in boiling water. Apparently less easily soluble in boiling dilute hydrochloric and nitric acids. Easily soluble in boiling dilute sulphuric acid. In hot alcohol and acetic acid (glacial) very easily soluble. In carbon disulphide, less easily. In hot aniline it is very easily dissolved, giving a red solution. Silver Beta-dinitroparabromphenylate. Preparation. The salt was made by mixing aqueous solutions of silver nitrate and ammonium dinitrobromphenylate. It is dif ficultly soluble in boiling water, but much more easily in alcohol. Analysis. NO, 0-4903 grams of substance yielded 0·1884 grams of AgCl. Properties. Splendid glittering red needles, having a brilliant green reflex. When dry the salt puffs on heating. If thrown on a hot surface, it explodes. Potassium Beta-dinitroparabromphenylate. I have already described the formation of this salt. It is somewhat difficultly soluble in boiling water. It forms long glittering and red needles, having a greenish reflex. This is the only salt that Körner prepared. He considers the play of colors to be like that of murexide. Barium Beta-dinitroparabromphenylate. Preparation.-Barium carbonate was boiled with a dilute alcoholic solution of the phenol until all carbonic anhydride was expelled. The residue was extracted with boiling water, filtered and allowed to crystallize. Analysis. (CH,(NO,),BrO),Ba=C,,H,K,01,Br,Ba 4 12 0.3824 grams of substance gave 0.1331 grams of BaSO, Properties. Saffron-yellow needles. Moderately soluble in hot water or alcohol. When heated in a mattrass, it explodes, covering the sides with carbon. * Armstrong, Ber. d. d. Chem. Ges., vi, 650. Ammonium Beta-dinitroparabromphenylate. Preparation. By action of ammonia on an alcoholic solution of the phenol. Analysis.— CH2(NO),BrONH=CH,N,O,Br 0-52 grams of substance gave 04 grams of PtCl,, 2AmCl. Properties.-Bright red silky needles. Soluble in boiling water and alcohol. When heated in a mattrass to 140°, it is volatile, forming a red sublimate which can be driven about by cautious heating. On higher heating it is dissociated into ammonia and phenol. A partial recombination takes place on cooling. Copper Beta-dinitroparabromphenylate. Preparation. It was obtained by action of a slight excess of well-washed CuCO, on the phenol in boiling dilute alcoholic solution. The resulting mass was dissolved in glacial acetic acid. The salt was thereby decomposed, cupric acetate and free phenol being formed. On diluting the blue solution carefully with water, a point was reached where the color changed to brown. The solution was then allowed to stand. After a short time the substance began to separate in crystals.* Properties. The salt crystallizes in short, brown glittering needles. It is insoluble in water and alcohol. Moderately soluble in boiling acetic acid. The best way to obtain it in solution, is to dissolve it in glacial acetic acid, and dilute with water until the blue color changes to brown. None of these salts contain water of crystallization and differ here from the salts of the isomeric dinitrobromphenol of Armstrong. When I found that this phenol could be so easily obtained, I hoped that by action of phosphorous pentabromide, it could be converted back into B-dinitroparadibrombenzol. All attempts in this direction have as yet failed. The larger part of the phenol remains unchanged on treatment with the bromide, while some of it is entirely decomposed. New Brunswick, N. J., April 1st, 1878. * It would be interesting to determine exactly at what point of dilution the acetic acid becomes equal to the phenol in its attraction to the copper. |