Evaluation of various force constants for the disubstituted benzenes is difficult and for complex sulpha drug molecules, it is very difficult. This paper assumes a simple force field model for the sulpha drug molecule by treating it as a para-disubstituted benzene molecule. The four C-C, two C-H and one C-N and C-S stretching force constants have been derived from that model using the reported experimental vibrational frequencies connected to the model. The derived values of stretching force constants are in good agreement with the reported values.

Whitmer et al. (1978) proposed a simple force field method in evaluating the force field in aromatics. They correlated the bond orders obtained by Hückel Molecular Orbital (HMO) theory and empirical methods to the force constants and improved upon the sample set of force constants generally observed in aromatic compounds to reproduce the frequencies observed in individual molecules. This method involves a lot of calculations. Further, the labor involved in determining the bond orders was wasted as a very simple force field was assumed. The problem can be simplified if an orthonormal set of symmetry coordinates is selected such that after symmetrization, G- and F-matrices contain diagonal terms only. Then each of the standard secular equations involves one force constant only and the force constants can be determined from the observed frequencies.

Physics Journal, Electrical Transport Properties, Transmission Electron Microscopy, Magnetotransport Data, Antiferromagnetic Semiconductors, Chemical Precipitation Method, Nanocrystalline Manganites, Perovskite Structure, Citrate-gel Method, Polycrystalline Perovskite Material, Debye Scherrer Formula.