Hindered Rotation II. The Hindered Rotation About the C–C Single Bond in Tetrachloroethane

Abstract

Because of the restriction to internal rotation, tetrachloroethane might consist of several rotational isomers: a cis‐(C_2v) form, a trans‐(C_2h) form, or forms intermediate to cis and trans with C₂ symmetry. From the Raman spectrum of C₂D₂Cl₄ and the spectrum of C₂H₂Cl₄ at different temperatures experimental evidence has been obtained which shows that the equilibrium mixture consists of two rotational isomers, the cis‐C_2v form and the C₂ form. The C_2v form was found to be the more stable, with a potential energy 1100 cal. per mole lower than the potential energy of the C₂ form.