Theoretical study of 2-selenophenecarboaldehyde in the gas and solution phases: Rotational barrier, energy difference and thermodynamic parameters

The syn- and anti-conformers of 2-selenophenecarboaldehyde have been studied in the gas and solution phases. A transition state has also been modelled for the syn-anti isomerisation. Computations in the gas phase have been done using different methods namely DFT/B3LYP, MP2 and CCSD(T) and the basis set used is 6-311++G(d,p). Solvent effects have been explored using the integral equation formalism in the Polarizable Continuum model and the DFT/B3LYP method. The optimised molecular structures and related parameters of these conformers are reported. The energy differences between the syn- and anti-con formers, associated rotational barrier and thermodynamic parameters have been derived from the computations. The infrared wavenumbers and Raman activities of these conformers are also reported with appropriate assignments. The results indicate that the structural parameters are not much different in the gas and solution phases. The syn conformer is more stable that the anti conformer both in the gas and solution phases with the rotational barrier being larger than the energy difference. Both of these energies increase slightly as the solvent becomes more polar. The results obtained are analysed and compared with the furan and thiophene analogues. (C) 2009 Elsevier B.V. All rights reserved.