The electrostatic term in molecular mechanics: 1-chloro-4,4-difluorocyclohexane and the cyclic ethylene ketal of 4-chlorocyclohexanone

Abstract

The performance of the controversial point—dipole formula (“Jeans equation”) is examined through molecular mechanics calculations on two molecules that contain dipolar bonds, 8-chloro-1,4-dioxaspiro [4.5] decane and 1-chloro-4,4-difluorocyclohexane. A general analysis is given of the total point—dipole interaction within a molecule, in terms of the separate dipole—dipole interactions. It is concluded that the set of bond moments in a polar moiety should not be replaced in computations by the overall group moment, as is sometimes considered. It is also stressed that the difference in electrostatic energy between conformations does not account necessarily for the total energy difference: differences in steric strain should not be ignored.