CONVENIENT SELECTIVE MONOACYLATION OF 1,N-DIOLS CATALYZED BY ION-EXCHANGE RESINS

Several 1,n-diols, ranging from 1,2-ethanediol to 1,16-hexadecanediol, were selectively monoacylated by transesterification in ester/octane solvent mixtures catalyzed by strongly acidic ion-exchange resins. Thi s method of selective esterification is quite simple and practical. Th e selectivity for monoester formation and initial rates of monoester f ormation depended on the ester/octane ratio of the solvents. The reaso ns for the selectivity are as follows: (1) The sulfonic acid-type ion- exchange resins usually contain 50-80% water, and a strongly acidic aq ueous layer is formed on the surface of the resins. (2) A partition eq uilibrium between the aqueous layer and the aprotic ester/octane layer is setup, and diols have higher partition coefficients than the produ ct monoesters. (3) Acylation of the alcohols occurs in the aqueous lay er and/or at the interface between the aqueous and the nonaqueous liqu id layer. (4) The formed monoesters move away from the aqueous layer i nto the aprotic layer.