ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 41, Number 6
JKCSEZ 41(6)
December 20, 1997 

The rate constants(kOH) for the alkaline hydrolysis of the 4-substituted phenyl ethyl benzylphosphonates were determined in various buffer solutions by UV-Vis spectrophotometer. The activation entropies of the title reactions show negative values and this result is not consistent with a dissociative mechanism (EA) for which a positive or slightly negative value of the entropy of activation should be expected. An associative mechanism(AE) is favorable because the negligible negative charge is generated on the leaving group in the rate determining step from a good Hammett relationship(ρ=1.89). By the results of a kinetic study, we conclude that a dissociative mechanism is not proceeded in the title reactions.