The study of proton shift behavior in nine families of disubstituted benzenes has provided quantitative correlations of internal and meta shifts among all families. The equations of correlation are useful in the prediction of shifts to an error of 0.015 ppm. The studies demonstrate shift additivity for the 4-substituted halobenzenes and suggest a chain rule relationship for substituent effects in those compounds. For that reason, previous theories of substituent interactions involving inductive and resonance contributors appear incorrect when applied to proton shift data. In decreasing order of up field shift at the ortho protons the substituents studied include N(CH3)2, NH2, OCH3, OH, F, CH3, CH2CH3, H, Cl, C(CH3)3, Br, CN, COOCH3, COOH, COCI, NO2. © 1973, American Chemical Society. All rights reserved.
D. W. Beistel et al., "The Internal Chemical Shift. A Key To Bonding In Aromatic Molecules. I. Internal Shift Correlations," Journal of the American Chemical Society, vol. 95, no. 17, pp. 5455 - 5460, American Chemical Society, Aug 1973.
The definitive version is available at https://doi.org/10.1021/ja00798a004
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01 Aug 1973