Effect of OHθand o-lodosobenzoate Ions on Dephosphorylation of Organo Phosphororus Ester in CTAX Micelle

This study deals with micellar effects on dephosphorylation of diphenyl-4- nitrophenylphosphate (DPNPPH), diphenyl-4-nitrophenylphosphinate (DPNPlN) and isopropylphenyl-4-nitrophenyl phosphinate (IPNPlN) mediated by or o-iodosobenzoate ion in aqueous and CTAX solutions. Dephosphorylation of DPNPPH, DPNPIN and IPNPIN mediated by or o-iodosobenzoate ion is relatively slow in aqueous solution. The reactions in CTAX micellar solutions are, however, much accelerated because CTAX micelles can accommodate both reactants in their Stem layer in which they can easily react, while hydrophilic and hydrophobic substrates are not mixed in water. Even though the concentrations $(>10^{-3}\;M)\;of\;OH^\Theta\;(or\;IB^\Theta)$ in CTAX solutions are much larger amounts than those of substrates, the rate constants of the dephosphorylations are largely influenced by the change of concentration of the ions, which means that the reactions are not followed by the pseudo first order kinetics. In comparison to effect of the counter ions of CTAX in the reactions, CTACI is more effective on the dephosphorylation of substrates than CTABr due to easier expelling of ion by ion from the micelle, because of easier solvation of ion by water molecules. The reactivity of IPNPlN with is lower than that of DPNPlN. The reason seems that the 'bulky' isopropyl group of IPNPIN hinders the attack of the nucleophiles.