Linear correlation between effective charge and bond length sensitivity to electronic effects in phosphoryl, sulfonyl, and sulfuryl compounds

Abstract

This work presents a linear correlation between bond length sensitivity (Δr/ΔpKlg) and effective charge by comparing a series of the following ROX compounds bearing phosphoryl (XP) and sulfonyl and sulfuryl (XS) moieties: phosphate monoester dianions and monoanions, phosphate diesters, phosphate and phosphorothioate triesters, 4‐Me, 3‐NO2 and 2‐ or 4‐NO2 substituted aryl benzene sulfonates, sulfate monoesters, and a previously determined series of sulfamate and mesylate esters. In every series for ROX compounds, the shortest C―O bond corresponds to the longest O―X bond, showing a linear correlation with the pKlg of the ROH parent compound. The chemical reasons for the extent of bond elongation are discussed, and a linear correlation is found between O―X bond length sensitivity and effective charge. These data show that bond length elongation depends on its strength regarding the equilibrium related to the full bond cleavage. Effective charges for phosphorothioate triesters and sulfonates are estimated, and the effective charge for aryl sulfamate esters is determined on the basis of the available linear free energy relationship data. It is expected that the observations of this paper will illuminate the effect of the electronic demand on the O―X bond lengths during phosphoryl, sulfonyl, and sulfuryl group transfer. Copyright © 2013 John Wiley & Sons, Ltd.

Charge density distribution and theoretical analysis of low and high energy phosphate esters

“…A similar strong correlation was observed for experimentally determined P-O e and C-O e distances. 61 For this reason we discuss these parameters jointly.…”