Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior

Brian Maurice Lynch

doi:10.1139/v77-075

journal article Feb 01, 1977

Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior

Brian Maurice Lynch

Canadian Journal of Chemistry Vol. 55 No. 3 pp. 541-547 · Canadian Science Publishing

View at Publisher Save 10.1139/v77-075

Abstract

The carbon-13 chemical shifts for 214 distinct sites (the 4-carbons) in 24 sets of 1-X,4-Y-disubstituted benzenes and for 270 distinct sites (the 1- and 2-carbons) in 16 of these sets are reproduced with excellent precision (correlation coefficients 0.99 or greater) either by linear proportionality relationships with the appropriate substituent chemical shift (scs) in a mono-substituted benzene (for the 4-carbons), or by simple additivity relationships with the scs (for the 1- and 2-carbons).Inconsistencies are pointed out in a theoretical rationalization of 4-carbon shifts used in discussing the non-additivity of these shifts in terms of a DSP approach, whereas the above one-parameter approach yields sets of proportionality constants (slopes of scs relative to Y = H) following systematic trends which are interpreted as results of changes in the excitation energy term at carbon-4 dependent upon the ionization potential of the group Y. There is no significant association between the scs slopes and sets of calculated CNDO/2 electron densities for these para-disubstituted benzenes.

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Published: Feb 01, 1977
Vol/Issue: 55(3)
Pages: 541-547
License: View

Authors

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Brian Maurice Lynch

Cite This Article

Brian Maurice Lynch (1977). Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior. Canadian Journal of Chemistry, 55(3), 541-547. https://doi.org/10.1139/v77-075

Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior

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