Arylazoglyoxalinecarboxylic acids / by Robert George Fargher.

  • Fargher, Robert George.
Date:
1921.]
Catalogue details

Licence: Public Domain Mark

Credit: Arylazoglyoxalinecarboxylic acids / by Robert George Fargher. Source: Wellcome Collection.

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    and separated in clusters of minute needles melting at 161° (corr.). This proved to be the monoacetate of the base (Found: C = 52*l; H = 4*8; N = 14T. C15H13N4Br,C2H402 requires C = 52*4; H = 4'4; N = 14*4 per cent.). Ammonium oxalate yielded a grey precipitate, which darkened rapidly on warming the solution. Addition of excess of sulphuric acid to the concentrated solution of the hydro¬ chloride caused, on stirring, the separation of a sparingly soluble sulphate, which crystallised in minute, flattened prisms. Ammoniacal silver nitrate was reduced in the cold. After separation of the above hydrochloride, no further crystal¬ line material was obtained, as the solution decomposed rapidly on exposure. The residue, after removal of tin from the soluble stanni- chlorides, amounted to only 0‘5 gram, and consisted mainly of ammonium chloride, although a little p-bromoaniline (007 gram) was isolated and identified by means of the acetyl derivative. Reduction with sodium hyposulphite in alkaline solution gave 2?-bromoaniline in a yield amounting to 52 per cent, of the theoretical, but no other pure substance was isolated. The form¬ ation of small quantities of a blue dye similar to that obtained by the reduction of nitroglyoxaline was observed. A:--p-Bro'mobenzeneazo-2-meihylglyoxaline-b-carboxylic A cid. This substance was prepared in a similar manner to the 2-phenyl homologue. Starting with 7‘52 grams of 2-methylglyoxaline-4 :5- dicarboxylic acid, the precipitate which formed was collected (A) and the filtrate acidified with hydrochloric acid, when 2 grams of pale orange crystals were obtained. These dissolved somewhat sparingly in alcohol, and separated in glistening, orange needles. The precipitate (A) was suspended in water and acidified with hydrochloric acid, when it gave 7 grams of an orange powder, con¬ sisting of a mixture of the azo-compound and the unchanged acid. Separation was effected by extraction with, and crystallisation from, alcohol, in which the original acid is practically insoluble, when 5*4 grams of 2-methylglyoxalinedicarboxylic acid were recovered unchanged. In a later experiment, the reaction was allowed to proceed for several hours, but although the yield of the product was larger, it was much darker in colour and more difficult to purify. The ultimate filtrates from the recrystallisation from alcohol yielded a small proportion of a product approximating in composition to 4 :5-bis-p-bromobenzeneazo-2-methylglyoxaline, but owing to the ease with which resinification took place, it was not obtained pure.