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- Title
<sup>17</sup>O NMR studies of ortho-substituent effects in substituted phenyl tosylates.
- Authors
Nummert, Vilve; Mäemets, Vahur; Piirsalu, Mare; Koppel, Ilmar A.
- Abstract
17O NMR spectra for 35 ortho-, para-, and meta-substituted phenyl tosylates (phenyl 4-methylbenzenesulfonates), 4-CH3-C6H4SO2OC6H4-X, at natural abundance in acetonitrile at 50 °C were recorded. The 17O NMR chemical shifts, δ(17O), of the sulfonyl (SO2) and the single-bonded phenoxy (OPh) oxygens for para and meta derivatives correlated well with dual substituent parameter treatment using the Taft inductive, σI, and resonance, σºR, constants. The influence of ortho substituents on the sulfonyl oxygen and the single-bonded phenoxy oxygen chemical shifts, δ(17O), was found to be nicely described by the Charton equation: δ(17O)ortho = δ(17O)H + ρI σI + ρR σ°R + δEsB 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 (SO2) 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 ( δEsB > 0, EsB < 0) was detected. Copyright © 2012 John Wiley & Sons, Ltd.
- Publication
Magnetic Resonance in Chemistry, 2012, Vol 50, Issue 10, p696
- ISSN
0749-1581
- Publication type
Article
- DOI
10.1002/mrc.3864