ISSN:
0749-1581
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
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 δSi 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.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260230512
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