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

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: (CDCl)-Cl-35=CHF, (CDCl)-Cl-37=CHF, (CHCl)-Cl-35=CDF, (CHCl)-Cl-37=CDF, (CDCl)-Cl-35-CDF, (CDCl)-Cl-37-CDF, (CHCl)-C-13-Cl-35-CHF, (CHCl)-Cl-35=(CHF)-C-13. Ground state rotational and quartic centrifugal distortion constants and diagonal elements of the nuclear quadrupole tensor (for both Cl-35 and Cl-37) 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.