A new topological index to elucidate apolar hydrocarbons.

A new topological charge-transfer index is applied to elucidate the polar character of hydrocarbons. The dipole moments calculated by algebraic and vector semisums of charge-transfer indices are defined in this work. The combination of the charge-transfer indices allows the estimation of the molecular dipole moments. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moment of a heterogeneous set of 57 polar and 53 apolar hydrocarbons. Linear and nonlinear correlation models are obtained. The new charge-transfer index, mu(vec), elucidates whether hydrocarbons are apolar, and improves the multivariable nonlinear regression equation for the dipole moment. When comparing with previous results, smaller superpositions of the corresponding pairs Gk, Jk are observed in our fits. This diminishes the risk of colinearity.