The absorption spectra of some substituted pyrazines and their salts / by Frank Tutin and Frederic W. Caton.

  • Tutin, Frank.
Date:
[1910?]
Catalogue details

Licence: In copyright

Credit: The absorption spectra of some substituted pyrazines and their salts / by Frank Tutin and Frederic W. Caton. Source: Wellcome Collection.

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    CCLV11I.—The Absorption Spectra oj Some Substituted Pyrazines and their Salts. By Frank Tutin and Frederic William Caton. In the preceding paper, the preparation of 2 : 5- and 2 : 6-diphenyl- pyrazine, pp'-dimethoxy^: 5- and -2: 6-diphenylpyrazine, and mm'p'pr-ietr am ethoxy-2 : 5- and -2 : 6-diphenylpyrazine is described. During the course of this work, certain remarkable colour changes were observed on treating these bases with acids, which suggested to us that a fuller investigation of the subject might lead to interesting results. Thus, whilst the hydrochloride of 2: 6-di¬ phenylpyrazine appeared colourless, the corresponding salts of the analogous pp'-dimethoxy- and ram'pp'-tetramethoxy-bases were bright yellow and orange-coloured respectively. Furthermore, on adding sulphuric acid to a chloroform solution of pp'-dimethoxy- 2 : 5-diphenylpyrazine, a yellow liquid which exhibited an intense, green fluorescence was first produced, whilst on the addition of an excess of the acid a very deep violet-coloured solution resulted. The further investigation of the bases in question rendered it evident that pyrazine derivatives, which have hitherto been stated to be monoacidic bases, in reality yield two series of salts, the di-acid salts being in all cases much more highly coloured than the corresponding derivatives containing but one equivalent of acid. The depth of colour of corresponding salts of analogous bases was found to increase with the accumulation of methoxyl groups, and to be somewhat greater in compounds of the 2 : 5-series than in the corresponding members of the 2 : 6 series. The colours of the salts obtained will be seen on reference to the following table:
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