Premium
17 O NMR spectroscopy: Effect of substituents on chemical shifts for p ‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates
Author(s) -
Balakrishnan P.,
Baumstark A. L.,
Boykin D. W.
Publication year - 1984
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270221204
Subject(s) - cinnamates , chemistry , benzoates , cinnamic acid , substituent , benzoic acid , acetone , methyl benzoate , medicinal chemistry , chemical shift , organic chemistry , stereochemistry
The 17 O NMR spectra for a series of 17 O‐enriched p ‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates in acetone at 40°C are reported. The carboxylic acids showed one signal (benzoic 250.5 ppm, SCS range p ‐MeO to p ‐NO 2 = 10.5 ppm; cinnamic 254.1 ppm, SCS range p ‐MeO to p ‐NO 2 = 5.4 ppm). The esters showed two signals [methyl benzoate (CO) 341.3 ppm and (OCH 3 ) 128.0 ppm; methyl cinnamate (CO) 339.9 ppm and (OCH 3 ) 134.2 ppm]. The SCS ranges for the carbonyls of the esters were larger than those for the corresponding acids, while those for the OCH 3 groups of the esters were slightly smaller. The carbonyl data gave good correlations with σ + constants, while the OCH 3 data gave at best only a poor correlation with σ constants. Dual substituent parameter treatment improved the correlations for all the data using σ R+ constants. The ratios of ρ I to ρ R+ were similar for all the sets of data.