17O 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, σº(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.