Reactions of alpha-nucleophiles with a model phosphate diester

Abstract

Substantial rate enhancements are observed for the reactions of -effect nucleophiles with 2,4dinitrophenyl ethyl phosphate diester 4. The effect is largest (ca. 4500-fold) for the hydroperoxide anion. However, the most reactive -effect nucleophile, and thus the most reactive nucleophile towards phosphate phosphorus at pHs near to or above its pK a of 13.74, is the hydroxylamine anion NH 2 O -. The kinetic reactivities of the -effect nucleophiles follow a Brnsted correlation, with a slope nuc = 0.410.03 greater than that (0.30) observed for non-effect nucleophiles, consistent with a thermodynamic origin for the effect.