Theoretical Study of the Structure of 2-Methylpropionyl Chloride in the Ground Electronic State: Potential Energy Surface of Internal Rotation of Isopropyl and Tow Methyl Groups

The geometric structure and isomerization of the 2-methylpropionyl chloride molecule in the ground electronic state in gaseous phase was studied using Ab initio methods (RHF, DFT, MP2 and QCISD). The potential energy surface (PES) and regions corresponding to transitions between conformers by the rotation of the isopropyl and two methyl groups was examined in one-dimensional approximation. The influence of the atomic orbital basis set and the method on the accuracy of the calculation of PES characteristics was considered. The calculation of the energy differences of conformers (DE) using reasonable basis sets provides values in good agreement with experimental results. The values of the potential barriers to gauche → gauche and cis → gauche transitions, and also the barrier of isopropyl and two methyl groups were compared with the same values for similar molecules as 2-methylpropanol and 2-methylpropionyl fluoride. (author)