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Int. J. Mol. Sci. 2000, 1(4), 84-91; doi:10.3390/ijms1040084
Article

A New Graphical Model for Proton NMR (De)shielding over a Carbon-Carbon Double Bond to Replace the Shielding Cone Model

*  and
Department of Chemistry, University of North Carolina at Wilmington, Wilmington, NC 28403-3297 USA
* Author to whom correspondence should be addressed.
Received: 5 June 2000 / Accepted: 25 August 2000 / Published: 14 November 2000
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Abstract

The long-held “shielding cone” model of the through-space NMR shielding effect of a carbon-carbon double bond predicts only the effect of the magnetic anisotropy of the double bond; it ignores other important contributors to the overall shielding. GIAO-SCF and GIAO-MP2 calculations have been performed on a simple model system, methane moved sequentially above ethene or 2-methylpropene. These calculations permit the net NMR shielding surface to be mapped. Based on those results, a new and very different graphical model for predicting the effect of a proton’s position relative to a carbon-carbon double bond on its chemical shift is presented.
Keywords: NMR; shielding cone; isotropic shielding; GIAO-SCF; GIAO-MP2; alkenes NMR; shielding cone; isotropic shielding; GIAO-SCF; GIAO-MP2; alkenes
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Martin, N.H.; Brown, J.D. A New Graphical Model for Proton NMR (De)shielding over a Carbon-Carbon Double Bond to Replace the Shielding Cone Model. Int. J. Mol. Sci. 2000, 1, 84-91.

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