Dipole Moment and Restricted Rotation in Some Chlorinated Hydrocarbons

Measurements of the variation of gas phase dipole moment with temperature of six chlorinated hydrocarbons are described. 1,2-dichloropropane, and, to a very small extent, 2,3-dichloropropene and 1,1,2-trichloroethane display a dependence of dipole moment on temperature. 1,4-dichlorobutane and the two isomers of 1,3-dichloropropene have dipole moments constant over the temperature range investigated. The results are analyzed both by adopting simple parametric functions to represent the potential hindering intramolecular rotation, and by computations of intramolecular energies.