Mechanistic Studies of 2-(1-Hydroxyethyl)-2,4,5-trimethyl-3- oxazoline Formation under Low Temperature in 3-Hydroxy-2-butanone/Ammonium Acetate Model Systems
作者:Hui-Yin Fu、Chi-Tang Ho
DOI:10.1021/jf960734o
日期:1997.5.1
Volatile compounds formed from the reaction of 3-hydroxy-2-butanone/ammonium acetate at 25, 55 and 85 degrees C were investigated. Six compounds were characterized by gas chromatography-mass spectrometry (EI and CI). Among the volatile compounds identified, an interesting intermediate compound, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline, was found. N-15-Labeled ammonium acetate was used to confirm the structure of 2-(P-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline. The formation pathway of these volatile compounds was proposed. In these model systems, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline was formed at the reaction temperature below 25 degrees C. On the other hand, tetramethylpyrazine was the major component when the reaction temperature was higher than 85 degrees C. The amounts of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline and tetramethylpyrazine increased linearly with the increasing heating time at 55 degrees C. Protic solvents did not promote 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation but did favor the formation of tetramethylpyrazine. A kinetic study of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation was also performed, and the activation energy was found to be 16.5 kcal/mol.