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.

    5/16 (page 2526)
    In order therefore to throw some light on the nature of these colour changes, some of the above-mentioned bases and certain of their salts have been examined spectroscopically in chloroform solution. This solvent was chosen as both the bases and their salts are sufficiently soluble in it, and, although it has a certain amount of general absorption in the extreme ultra-violet region of the spectrum, it was thought that it would not interfere appreciably with the results. Moreover, the salts of the pyrazines have much less tendency to hydrolyse when dissolved in chloroform than in alcoholic solution.* The curves obtained from 2 :6-diphenylpyrazine, y^-dimethoxy- FiCr. 1. Oscillation frequencies. - 2 : 6-Diphenylpyrazine . 2 : 6-Diphenyl'pyrazine hydrochloride. -— 2 : 6- Diphenylpyrazine hydrobromicle. 2 : 6-diphenylpyrazine, and mm'ppf-tetYa,methoxy-2 : 6-diphenyl¬ pyrazine are shown in Figs. 1, 2, and 3 respectively. From these it is seen that each of the bases shows absorption in the ultra-violet part of the spectrum, and that salt-formation is accompanied by a considerable shift of the bands towards the red end, thus accounting for the development of colour on treatment with acids. In the case of 2: 6-diphenylpyrazine hydrochloride, which is practically colourless, the absorption bands still lie within the ultra-violet * Even when employing chloroform as a solvent for the salts it was necessary to have a certain excess of thejrespective acid in the solution.