The addition of cyanide ion to N-alkyl-3-carbamoylpyridinium ion in hexadecyltrimethylammonium bromide reversed micelles: the effects of alkyl chain length

Abstract

The addition of cyanide (CN^–) ion to N-alkyl-3-carbamoylpyridinium ion (alkyl derivatives) with various alkyl chains in water pools of the reversed micellar system, water/hexadecyltrimethylammonium bromide (HTAB)/chloroform–iso-octane (3 : 2, v/v) has been determined spectrophotometrically. The results of the reaction series are examined with respect to the molar ratio of water to HTAB, R, and the CN^– ion concentration in the water pool, [CN^–]_aq, in order to study the effect of the alkyl chain length of the alkyl derivatives on the addition reaction in HTAB reversed micelles. The rate constant, k_2w, and the equilibrium constant, K_w, are evaluated on the basis of the dispersed water pools in the micellar system as the space for reaction.

Based on the behaviour of k_2w and K_w with R, the present results are obtained. The addition reaction proceeds favourably with decreasing R and with increasing alkyl chain length of the alkyl derivatives. Furthermore, the reaction tends not to be affected significantly by water content in the reversed micelles with increasing alkyl chain length.

The effect of CN^– ion concentration in water pools on k_w and k_2w suggests that the reverse reaction for the longer alkyl derivatives is highly affected by CN^– ion concentration compared to that for the shorter alkyl derivatives.

The behaviour of k_2w and K_w with R and [CN^–]_aq is interpreted mainly on the basis of the different localizations of respective alkyl derivatives in the water pool.