Microwave and high resolution infrared spectra of vinyl chloride, ab initio anharmonic force field and equilibrium structure

Abstract

The quadratic, cubic, and semi-diagonal quartic force field of vinyl chloride has been calculated at the MP2 level of theory employing a basis set of triple- ζ quality. The spectroscopic constants derived from this force field are compared with the experimental values. To make this comparison more complete, the rotational constants of the lowest excited state, v 9 = 1 at 395 cm −1 have been determined by microwave spectroscopy and the ν 12 band (around 618 cm −1) has been investigated by high-resolution infrared Fourier transform spectroscopy. The equilibrium structure has been derived from experimental ground state rotational constants and ab initio rovibrational interaction parameters. This semi-experimental structure is in excellent agreement with the ab initio structure calculated at the CCSD(T) level of theory using a basis set of quintuple- ζ quality and a core correlation correction. The experimental mass-dependent r m structures are also determined and their accuracy is discussed. The recommended equilibrium geometry is: r (C C) = 1.3262(10), r (C Cl) = 1.7263(10), r (C H g ) = 1.0784(10), r (C H c ) = 1.0795(10), r (C H t ) = 1.0797(10), ∠(CCCl) = 122.77(10)°, ∠(CCH g ) = 123.86(10)°, ∠(CCH c ) = 121.80(10)°, ∠(CCH t ) = 119.29(10)°.