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An equation utilizing empirically derived substituent constants for the prediction of vicinal coupling constants in substituted ethanes
Author(s) -
Colucci William J.,
Jungk Steven J.,
Gandour Richard D.
Publication year - 1985
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260230512
Subject(s) - vicinal , substituent , chemistry , torsion (gastropod) , coupling constant , dihedral angle , computational chemistry , crystallography , hydrogen bond , stereochemistry , molecule , organic chemistry , quantum mechanics , physics , medicine , surgery
A simple equation has been developed for the prediction of vicinal coupling constants in HCCH fragments:\documentclass{article}\pagestyle{empty}\begin{document}$$ ^{\rm 3} J{\rm (\theta)} = {\rm}A + B{\rm cos \theta} + C{\rm cos 2\theta} + {\rm cos \theta [(}\Delta {\rm S}_{\rm 1} + \Delta {\rm S}_{\rm 4} {\rm) cos (\theta} - {\rm 120)} + {\rm (}\Delta {\rm S}_{\rm 2} + \Delta {\rm S}_{\rm 3} {\rm) cos (\theta} + {\rm 120)]} $$\end{document}The equation is a cosine series in θ, the torsion angle between vicinal hydrogens. The feature which distinguishes this equation from similar equations is the inclusion of δ S i terms, which describe the magnitude of each substituent's effect. These substituent constants have been defined from experimental data. An orientation effect which is dependent on the torsion angle(s) between substituent(s) and a vicinal hydrogen is included. Substituent constants have been defined for 39 groups, of which 15 have been experimentally determined herein. The parameters for the equation have been defined from 49 torsion angles in 19 conformationally rigid compounds. The torsion angles have been determined from x‐ray crystal structure data and molecular mechanics calculations. The multiplicity of structures used to determine the substituent constants should allow for the application of this equation to a wide variety of structures.