Molecular structure of both trans and cis conformers of XC(O)OY (X, Y=F and Cl) molecules were determined employing ab initio molecular orbital technique and density functional theory (DFT) method. Different vibrational correction schemes were applied to correct the bond lengths obtained from the ab initio methods. BLYP and B3LYP methods of DFT were used to optimize the molecules. The atomic basis sets 6-311++G (2d,2p) and 6-311++G(3df,3pd) were used for the above methods. Potential energy surface scan was performed for the FC(O)OF molecule at HF/6-31G*, MP2/6-31G*, BLYP/6-311++G(2d,2p) and B3LYP/6-311++G(2d,2p) levels of theory, and interconversion barrier from cis to trans was calculated and these values were found to be 40.06, 42.72, 47.02 and 54.01kJ/mol respectively and for the same, the experimental value was found to be 35kJ/mol. The ΔE (E cis −E trans ) values were computed at HF-SCF, electron correlated and DFT methods. The various basis sets from a very small size to a very large size i.e., basis sets were used for the ΔE calculation. Nowek et al. have also reported the ΔE values both at ab initio and DFT methods for the FC(O)OF molecule. The complete spectrum of ΔE values of the FC(O)OF molecule is now available and it is a suitable testing bed for experiment and theory. The higher basis set of BLYP level of theory reverses the order of conformation. The ΔE values for the FC(O)OF, ClC(O)OF and ClC(O)OCl molecules were obtained at HF, MP2, BLYP and B3LYP levels of theory. The values of BLYP level of theory is not found to be close to the other theoretical values. The DFT parameters such as chemical hardness and chemical potential were used to discuss the conformational stability of the molecule. The Fourier decomposition for the rotational potential energy of the FC(O)OF molecule are studied.