STUDY OF PYRAZINE FORMATION

The volatiles isolated from the reaction mixture of a D-glucose and ammonia model system were identified using the gas chromatographic retention indices and the gas chromatographic-mass spectrometric technique. The principal constituents of the dichloromethane extract of the above reaction mixture were imidazoles, pyrazines, and pyrroles. The identification of 5-imino-2-methyl-l-cyclopentenol is further evidence that 2-methyl-l-cyclopentenol-5-one could be a precursor of cyclopentapyrazines. The dehydrogenation of 2, 3, 5-trimethyl-5, 6-dihydropyrazine was conducted in ethanol-KOH solution under acidic and basic conditions. When the reaction mixture was treated with acid, 2, 5-dimethyl-, 2, 6-dimethyl-,2-ethyl-3, 6-dimethyl-, 2-ethyl-3, 5-dimethyl-, tetramethyl-, and 2-ethyl-2, 3, 5-trimethylpyrazine were obtained in addition to 2, 3, 5-trimethylpyrazine and unreacted dihydropyrazine. This indicated the presence of dihydropyrazine carbanions, which participated in introducing ethyl groups of solvent ethanol to pyrazine rings, in the reaction system. © 1979, American Chemical Society. All rights reserved.