Basicity of amides in water and in aqueous micellar solutions of SDS. Their influence on micellar structure

Abstract

The acidity constants of the protonated forms of some amides, including formamide, N-methylformamide, N,N-dimethyl-formamide, N-methylacetamide and N,N-dimethylacetamide, have been determined in water and in aqueous micellar solutions of sodium dodecyl sulfate (SDS). The influence of these amides on the acid hydrolysis of 1-phenylethylnitrite was studied by UV absorption spectroscopy. The observed inhibition, in water as well as in an aqueous micellar medium, in the reaction rate by the presence of amides has been quantitatively interpreted by considering the action of amides as weak bases. Solvent effects at high amide concentrations were also considered. The experimental kinetic data obtained in the presence of SDS were analysed using the simple pseudophase ion-exchange model and taking into account the effects of amides on the structure of micelles.