Basic hydrolysis of carbamates in micellar environment

Abstract

The structure of carbamates have a great influence on the rate of the reaction of basic hydrolysis of carbamates at pH 11.2 and temperature 10 oC. The reaction will occur under this condition only when the structure of the carbamate can produce either cyclic of isocyanate intermediate. The carbamate derivatives Phenyl N-phenylcarbamate (I), Phenyl. N-methyl-N-phenyl carbamate (II), Phenyl N-(o-carboxyphenyl) carbamate (III), Phenyl N-(p-carboxyphenyl) carbamate (IV), Phenyl N-methyl-N-(o-carboxyphenyl) carbamate (V), and Phenyl N-methyl-N-(p-car-boxyphenyl) carbamate (VI) were studied. The compound No.II and VI can not be followed and in the aqueous solution, the reaction rate (km) is completely reverse, namely; V > I ≈IV > III But in the micellar environment the order of the reaction rate (km) is completely reverse, namely; III > IV > I > V The reaction in the micelle is follow Scheme 1. 1 M + S K (M8) The result of this experiment shows the catalytic effect of cationic micelles kw km Product Scheme 1 of cetyltrimethylammonium bromide (CTAB) by 6-570 times faster than without micelle. The kinetic ratios (km/kw) being all greater than one in all cases indicated that the reaction within the micelle is more predominant than outside the micelle. The location of the substrates also plays the importance roles in the micellar environment.