Infrared spectra of some isotopomers of methylamine and the methylammonium ion: a theoretical study

The normal mode frequencies of some isotopomers of methylamine and the methylammonium ion are examined theoretically using the GAUSSIAN 94 set of quantum chemistry codes. In particular, deuteration of the NH2 and NH3+ hydrogen atoms, as well as the deuteration of the CH3 hydrogen atoms, and total deuteration of both methylamine and the methylammonium ion are examined. Calculations are performed at the Hartree-Fock (HF) and second-order Moller-Plesset (MP2) levels of theory using a 6-311G** basis set. Correction factors for predominant vibrational motions at each level of theory are reported and compared for the eight molecular species that are considered. (C) 1998 Elsevier Science B.V.