Rotational isomerism. Part XX. Relative conformational stabilities of some chlorofluoropropanes

Abstract

A combination of classical conformational-energy calculations and variable-temperature n.m.r. analysis was used to determine the relative conformational stabilities of CFCl₂·CHCl·CCl₃, CFCl₂·CHCl·CFCl₂. and CF₂Cl·CHCl·CFCl₂. The analysis of the variable-temperature data was carried out using a specially written least-mean-squares routine considering explicitly uncertainties in both the coupling constant and temperature measurements. Although 1.3-interactions play an important role in determining conformational stability in these systems, the attractive polar interactions between fluorine and carbon and hydrogen atoms are also found to play an important and sometimes dominant role.