Analysis of Conformations of Six-, Seven-,and Eightmembered Sulfur-Containing Heterocycles by Ab initio calculations

Ab initio Hartree_Fock calculations at the HF/6-31G*level of theory for geometry optimization and the MP2/6-31G*//HF/6-31G* and B3LYP/6-311G(2df,p)//HF/6-31G* levels for a single point total energy calculation are reported for the important energy minimum conformations of trans and cis forms of 2,3- diacetyl-1,4-dithiane (1), 2,3- diacetyl-1,4-dithiepane(2), and 2,3- diacetyl-1,4-dithiocan (3). According to the HF/6- 31G*calculations the trans di-equatorial of 2 and 3 are the most stable conformers but the cis isomer of 1 is more stable than the others.