Infrared spectra of two isotopomers of isopropylphosphine: A theoretical study

The normal mode frequencies and the corresponding vibrational assignments of the s-trans and gauche conformers of isopropylphosphine-d0 and isopropylphosphine-PP-d2 are examined theoretically using the Gaussian 94 set of quantum chemistry codes at the MP2/6-311G** and DFT/B3LYP/6-311G** levels of theory. By comparison to experimental normal mode frequencies deduced by Durig and Cox [J. R. Durig and A. W. Cox, Jr., J. Chem. Phys. 80, 2493 (1976)] correction factors for predominant vibrational motions are reported and compared. Energetic differences as well as thermodynamic function differences between the s-trans- and gauche-conformers are considered. It is found at the MP2 and DFT levels of theory that the gauche conformer is more stable by 0.54 kJ/mol and 0.28 kJ/mol, respectively.