Trapping of the Intermediate Formed in the E1cB Hydrolysis of Some Alkyl and Aryl N-(4-Nitrophenyl) carbamates in a Hydroxy Functionalized Micelle

Abstract

The basic hydrolyses of some alkyl and aryl N-(4-nitrophenyl) carbamates in the presence of micelles of cetyl (2-hydroxyethyl) dimethylammonium bromide ( chedab )were studied. For compounds which react by the B_AC2 mechanism, verysimilar results were obtained in cetyltrimethylammonium bromide ( ctab ) and in chedab micelles.

However, for compounds which react by the E1cB mechanism, the intermediate p- nitrophenyl isocyanate was trapped by the hydroxy group of the functional micelle to form a new carbamate directly bound to the detergent molecules of the micelle. It was shown that this new carbamate decomposed by a B_AC2 mechanism.

p- Nitrophenyl isocyanate added to an alkaline solution of chedab gave N-(4-nitrophenyl)- carbamate ion. Thus, the isocyanate has to be generated within the micelle for trapping to occur. The rate of reaction of p-nitrophenyl isocyanate with OH^-/H₂O is faster than the rate of solubilization within the micelle.