17 O NMR studies of ortho ‐substituent effects in substituted phenyl tosylates

17 O NMR spectra for 35 ortho ‐, para ‐, and meta ‐substituted phenyl tosylates (phenyl 4‐methylbenzenesulfonates), 4‐CH 3 ‐C 6 H 4 SO 2 OC 6 H 4 ‐X, at natural abundance in acetonitrile at 50 °C were recorded. The 17 O NMR chemical shifts, δ ( 17 O), of the sulfonyl (SO 2 ) and the single‐bonded phenoxy (OPh) oxygens for para and meta derivatives correlated well with dual substituent parameter treatment using the Taft inductive, σ I , and resonance, σ º R , constants. The influence of ortho substituents on the sulfonyl oxygen and the single‐bonded phenoxy oxygen chemical shifts, δ ( 17 O), was found to be nicely described by the Charton equation: δ ( 17 O) ortho = δ ( 17 O) H + ρ I σ I + ρ R σ ° R + δE s B when the data treatment was performed separately for electron‐donating + R substituents and electron‐attracting − R substituents. Electron‐attracting meta and para substituents in the phenyl moiety caused deshielding while the electron‐donating meta , para and ortho + R substituents produce shielding effects on the sulfonyl (SO 2 ) and single‐bonded phenoxy (OPh) oxygens. The influence of ortho inductive and resonance effects in the case of + R substituents was found to be approximately twice higher than the corresponding influence from the para position. Due to the steric effect of ortho substituents a decrease in shielding of the oxygens at the sulfonyl group ( δE s B > 0, E s B < 0) was detected. Copyright © 2012 John Wiley & Sons, Ltd.