Abstract
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 1J(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 3J(C-5, H) values depend on the corresponding dihedral angle and the spatial relationships of the C=N double bond and the aryl group.
Key Words: (C, H) coupling constants, Nitrogen lone-pair, Carbonyl group, INDO-FPT calculations, Diazepam
South African Journal of Chemistry Vol.57 2004: 37-39