DOI:10.1002/(SICI)1097-461X(1997)62:5<477::AID-QUA4>3.0.CO;2-T

Atomic charges derived from different methods. A comparative study applied to SO2 heterocycles.

Atomic charges were calculated at ab initio level using different methods of charge determination to compare them and estimate their utility in the electronic description of heterocycles containing the SO₂ moiety. Those procedures implemented on the Gaussian92 program were included [Mulliken population analysis, Weinhold-Reed natural population analysis (NPA) and CHELPG]. The first two are based on the molecular orbitals while in the third one the charges are derived by fitting the electrostatic potential. Two sets of compounds were chosen to represent the different characteristics of the SO₂ heterocycles studied: simpler five-member heterocycles and SO₂ small derivatives. These molecules were optimized at the HF/6-31G^* level and their energy evaluated by a punctual calculation MP2/6-31G^*//HF/6-31G^*. The dipole moments for these molecules were obtained by using all the methods previously mentioned and compared with the SCF, MP2, and experimental dipole moments. The influence on the charges of some atoms by changing the electronegativity of neighboring atoms has also been investigated for these compounds. The results obtained show that the best methods to describe the electronic distribution of the oxathiole studied are Mulliken and CHELPG at the MP2 level of calculation. The charge distributions obtained with these two methods for these particular heterocycles are discussed.