Formation of pyridines from thermal interaction of glutamine or glutamic acid with a mixture of alkadienals in aqueous and oil media

A mixture of alkadienals containing equimolar concentrations of (t,t)-2,4-heptadienal, (t,t)-2,4-nonadienal, and (t,t)-2,4-decadienal was heated at 180C with glutamine or glutamic acid in the ratio of individual 2,4-alkadienals to amino acid of 1:1:1:1 in aqueous and oil media where glutamine could generate free ammonia readily but glutamic acid could not. When the mixture of three alkadienals was reacted with glutamine, the total amounts of alkylpyridines were much higher in the oil systems even though some alkylpyridines, such as 3-butylpyridine, 3-pentylpyridine, and 4-pentylpyridine, could only be found in the aqueous systems. In the interaction of the mixture of three alkadienals with glutamic acid, only three 2-alkylpyridines including 2-ethylpyridine, 2-butylpyridine, and 2-pentylpyridine, which could be formed directly from the corresponding alkadienals, were produced under both conditions.