PHOSPHATE CLEAVAGE BY ORGANOIODINANE OXYANION ANALOGS OF O-IODOSOBENZOATE - EXPERIMENTAL AND COMPUTATIONAL STUDIES

1,3-Dihydro-1-oxido-3-methyl-1, 2,3-benziodoxaphosphole 3-oxide (4) an d 1-H-1-oxido-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide (5) were use d to cleave p-nitrophenyl diphenyl phosphate (PNPDPP) (2) in aqueous m icellar cetyltrimethylammonium chloride (CTACI) in phosphate buffer at pH 8. The maximum pseudo-first-order cleavage rate constants (with 1. 0 x 10(-4)M 4 or 5 and 1.0 x 10(-5) M 2) were 0.0016 s(-1) for 4 ([CTA C1] = 0.01M) and 0.0013 s(-1) for 5 ([CTAC1] = 0.001M). Reagents 4 and 5 were, respectively, 44 and 57 times less reactive toward PNPDPP tha n iodosobenzoate (1) under comparable conditions. Ab initio electronic structure calculations were carried out on 1, 4 and 5 and their proto nated forms. Calculated structural parameters were compared with cryst allographic data where possible, The computed atomic net charge on the oxide oxygens of 1, 4 and 5 was found to track the reactivity toward PNPDPP.