On the alkylation of tributylphos-phinecobaloxime(s) by alkyl chlorides

The variation in the rate constants (k) for the alkylation of tributylphosp hinecobaloxime(s) by some alkyl chlorides (RCl) is explained in terms of th e equation: logk = rho(sigma*-nu) + logk(0), where sigma* is Taft's polar s ubstituent constant for an alkyl group R, nu a dummy variable defined to ha ve zero value for the R groups having sigma* < 0.405 and non-zero values ot herwise, rho the regression coefficient and the subscript 0 refers to the s ituation where (sigma* - nu) = 0. An analysis of the nature of nu reveals t he ambivalent nature of sigma* operative in the alkylation reaction - the f actor which favours the reaction also acts against it.