Cryochemistry. Esterification in frozen dioxane solution

The freezing effect on esterification of acids of different polarity has be en investigated in dioxane solution and compared with the results obtained in liquid phase. The methyl eater of benzoic, salicylic, 3,5-dinitrobenzoic and maleic acid, respectively, has been synthetized by DCC-activated coupl ing and DMAP-catalysis. The results have been evaluated by RP-HPLC analysis . The freezing of the dioxane solutions resulted a significant increase of yield of methyl benzoate, however, ester formation of the other acids becam e nearly similar in liquid and frozen conditions. The role of freezing and polarity of the acids in the ester yield is discussed.