The conformations and electronic structures of 1, 3-difluoropropane have been investigated by ab intio and density functional methods. The GG conformer is the most stablle, and the AG conformer is the second. The gauche effect is evaluated from electrostatic interaction. The energies by the van der Waals' parameters of MM2 force field seem to be reasonable. The populations of conformations at HF/6-31G^* and HF/6-31+G^*^* levels are accorded with the experimental results for GG and AG conformers.

Key words: AB INITIO CALCULATION, ELECTRONIC STRUCTURE, CONFORMATION, PROPANE P, DIFLUOROMETHANE P, THEORETICAL CALCULATION