oa South African Journal of Chemistry - The Dependence of 1J(C, H) and 3J(C, H) on a Nitrogen Lone-pair and Carbonyl Group. Application to Diazepam
The relatively large difference in the directly bonded (C, H) coupling constants of the C(3) methylene group in diazepam can be attributed to the spatial relationship of the C(3)-H bonds and the C(2)=O group and N(4)-lone pair. INDO-FTP calculated <sup>1</sup>J(C-3, H) values reveal a linear relationship with the C(2)-C(3)-N(4)-C(5) dihedral angle, a non-linear relationship with the C-H bond length and small negative change depending on the N(1)-C(2)-C(3)-N(4) dihedral angle. The INDO-FTP calculated <sup>3</sup>J(C-5, H) values depend on the corresponding dihedral angle and the spatial relationships of the C=N double bond and the aryl group.
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