An application of the semi-empirical CNDO/2 and INDO methods to calculate the molecular dipole moment of iodine compounds has been made with all-valence electron scheme. Equilibrium geometries are obtained using experimental bond lengths and the various semi-empirical parameters required inscf-mo scheme are obtained from atomic Hartree-Fock calculations and by comparison withab initio calculations. Bothsp andspd valence basis sets are used.

A theoretical study on the conformation of allyl halides from the calculation of nuclear spin-spin coupling constants by adopting the finite perturbation theory (FPT), is carried out in terms of the self-consistent, semi-empirical INDO (intermediate neglect of differential overlap) approximation of molecular orbital theory. Results of the calculations performed using ‘s’ and ‘p’ valence orbitals alone (‘sp’ basis) at INDO level approximation seem to replicate the experimental trend quite satisfactorily. Despite the overall agreement of the theoretical values with the experimental ones, the uncertainties in the INDO parametrization scheme lead to overestimation of certain coupling constants. The calculations also show that the orientation of the coupled protons with respect to the substituent halogen atom is an important factor to be considered.