A theoretical study of the molecular structure and vibrational spectra of methyl cyanate and its sulfur and selenium analogues

Ab initio electronic structure calculations at the MP2, Becke3LYP, and CCSD levels in conjunction with 6-311++G(d,p) basis set are used for determinin g the structure of equilibrium and the top-of-barrier methyl conformers of CH3-XCN (X = O,S,Se) molecules, Energy minimum structures for all substitue nts correspond to the staggered and top-of-barrier structures to the eclips ed conformations, each having C(s)point-group symmetry. Ar the MP2 and Beck e3LYP levels vibrational analysis was performed. For methyl cyanate and met hyl thiocyanate, the theoretical IR spectra are compared with the experimen tally obtained values. For the structural and vibrational parameters, there is excellent agreement between the theoretical and the available experimen tal data. (C) 2000 Elsevier Science B.V. All rights reserved.