Conformational behaviors of 2, 5-dimethoxy-2,5-dimethyl-1,4-dithiane (compound 1) and
2,5-dimethyl-2,5-bis (methylthio)-1,4-dithiane (compound 2) were investigated by computational
methods including B3LYP/6-311+G** and M06-2X/6-311+G** levels of theory and NBO analysis.
The stereoelectronic effect of axial, axial (ax, ax) and equatorial, equatorial (eq, eq) conformations
was studied using NBO analysis. Using NBO analysis, the values of the stereoelectronic effects were
calculated through the energy of stability associated with the electron transfers of compounds 1 and
2. The results showed that the eq, eq conformations of the studied compounds were more stable than
their corresponding ax, ax conformations, and LP2X→σS1-C2 and LP2S→σ*C2-X electron transfers
play important roles in the conformational behavior of the studied compounds. The main purpose
of the present work was to study the effects of stereoelectronic interactions and steric on the
conformational superiority of the di-methoxy (compound 1) and di-thiomethyl compounds (compound
2). Thus, the values of resonance stability energy, non-diagonal elements, and orbital populations
were investigated. Also, active electrophilic and nucleophilic centers were identified using
fronting orbitals analysis obtained by DFT methods. The electrostatic potential maps of the title
compounds were investigated at the B3LYP/6-311+G* level of theory. All of the NMR parameters
and geometrical properties of both compounds were determined in this study.