Rotational study on the van der Waals complex 1-chloro-1,1-difluoroethane-argon.

The rotational spectrum of the van der Waals complex formed between 1-chloro-1,1-difluoroethane and argon has been investigated by using a pulsed jet Fourier transform microwave spectrometer. Only one set of rotational transitions belonging to the lowest energy conformer has been observed and assigned, although theoretical calculations suggest six stable conformers that might be observed. The observed conformer, according to the experimental evidence from two isotopologues (35 Cl and37 Cl), adopts a configuration in which the argon atom is located, close to the CF2 Cl top, between the CCF and CCCl planes (the dihedral angle ∠ArCCCl is 65.2°). The distance between argon atom and the center of mass of CH3 CF2 Cl is 3.949(2) Å. The dissociation energy, with pseudo diatomic approximation, is evaluated to be 2.4kJmol-1 .