Properties of Alkylpyrazines

Electric dipole moments of methylpyrazines have been reported methylpyrazine, 0.74D (663) 2,5-dimethylpyrazine, 0.0 and 2,6-dimethylpyrazine, 0.53, 0.6, and 0.66(659,663,664). 

2-Methylpyrazine in the presence of excess potassium amide at — 40° undergoes deprotonation to give the charge delocalized anion (10) (665). 

Methylpyrazine is methylated with methyl iodide in dimethyl sulfoxide at room temperature to give l-methyl-3-methylpyrazinium iodide and i-methyl-2-methyl-pyrazinium iodide, in a ratio of 3.9 I. The rate of methylation relative to pyrazine was 2.06 (666). The reaction of 2,5-dimethylpyrazine with iodo- or bromoacetic acid to give the 1,2,5-trimethylpyrazinium salt has been investigated (3). A kinetic study of the reaction of sodium hydroxide on quaternary pyrazinium salts (667, 668) has been made using a conductivity method to follow the progress of the reaction (11=5 12). In the case of 1,2,5-trimethylpyrazinium hydroxide, equilibrium lies toward (11), which slowly disappears, presumably forming the ether (13) (668). When 1,2,5-trimethylpyrazinium bromide was heated in a sealed tube trimethyl- and tetramethylpyrazine were produced (660). 

Comparison between the photoelectron spectra of pyrazine, 2,6-dimethylpyrazine, and tetramethylpyrazine suggests a different behavior toward electrophilic attack on tetramethylpyrazine compared to the others (585). 

Irradiation of 2-methylpyrazine and 2,5- and 2,6-dimethylpyrazine at 254 nm has been shown to give various methyl- and dimethylpyrimidines (632). Pyrolyses and thermal stabilities of 2,5-dialkylpyrazines have been examined (688a). 

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Masuda H. and Mihara S. (1988) Olfactive properties of alkylpyrazines and 3-substituted 2-alkylpyrazines. J. Agric. Food Chem. 36, 584. 

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