Acyl migration in glycerides. I. A bimolecular resonant ion complex as intermediate in acyl migration of monoglycerides

Abstract

Acyl migration and the rate of racemization of D- and L-monostearin and the rate of conversion of 2-monostearin into DL-isomer catalyzed by hydrogen chloride under anhydrous conditions have been studied. It was found that the rate of racemization and the rate of conversion differ considerably under identical conditions. The rate of racemization and the rate of conversion of these three isomers into DL-monostearin increases as follows: D-monostearin, L-monostearin and 2-monostearin. 2-Monostearin is one of the most unstable isomers and is completely convertible into DL-isomer (100%). The rate of the racemization of D- and L-monostearin to DL-isomer coincides perfectly with the rate of the conversion of these two isomers into bismonostearin ethers. D-monostearin is inherently more than twice as stable as L-isomer. All four isomers were converted into bismonostearin ethers. The synthesis of the bismonostearin ethers is described. The formation of a bimolecular resonant ion complex as an intermediate in acyl migration is suggested.