Molecular structure of cis-1-chloro-2-fluoroethylene from ab initio calculations and microwave spectroscopy

Abstract

The molecular structure of cis-1-chloro-2-fluoroethylene has been investigated both theoretically and experimentally. As far as ab initio computations are concerned, the equilibrium geometry has been evaluated using the coupled-cluster approach [CCSD(T)] and basis sets of triple and quadruple zeta quality. Accurate results are presented. A recommended equilibrium geometry, obtained by adding ad hoc corrections, is also given. The centimetre and millimetre-wave spectra of the following 8 isotopomers have been observed: CD³⁵ClCHF, CD³⁷ClCHF, CH³⁵ClCDF, CH³⁷ClCDF, CD³⁵ClCDF, CD³⁷ClCDF, ¹³CH³⁵ClCHF, CH³⁵Cl¹³CHF. Ground state rotational and quartic centrifugal distortion constants and diagonal elements of the nuclear quadrupole tensor (for both ³⁵Cl and ³⁷Cl) have been accurately determined. The structure of cis-1-chloro-2-fluoroethylene has been experimentally determined for the first time by isotopic substitution, employing three independent methods. A comparison between the experimental and theoretical geometry is also presented.