THE PREPARATION OF SUCROSE MONOESTERS

Abstract

The Snell procedure for the preparation of sucrose monoesters of the higher saturated fatty acids by transesterification of sucrose and methyl esters in N,N-dimethylformamide was found to yield variable results due to the use of solid potassium carbonate as catalyst and to impurities in the solvent. A kinetic study of the reaction revealed that yields of sucrose ester and rates of reaction were reproducible when conditions for homogeneous catalysis were established. The reaction followed first-order kinetics in methyl ester and sucrate ion and the rate of reaction was essentially independent of the sucrose concentration, the molecular weight of the fatty acid, and the nature of the metal sucrate used to catalyze the reaction. The activation energy for the reaction was 9.9 kcal mole⁻¹. Equilibrium constants for the principal reactions were determined, and it was established that only the thermodynamic product prevailed at any time throughout the transesterification reaction. A preparative method for the synthesis of sucrose monoesters was developed that gave yields of sucrose ester, based on the amount of methyl ester which had reacted, which were essentially quantitative. The product contained about 20% of di-and 80% of mono-ester.