Abstract:
It is demonstrated that the variation of the gas-phase basicities of amines can be analyzed by using two parameters: one global and one local (that is, site-dependent). Two global quantities (the average "effective" electronegativity and the geometric average of the isolated-atom electronegativities) and two local quantities (the fukui function and the residual charges) are tested. A two-parameter linear model containing one global and one local quantity produces satisfactory correlations with the experimental gas-phase basicities. It is shown how to express the fukui function, which reflects the site reactivity in density functional theory (f(r⇒) = [∂ρ(r→)/∂N]ν(7), in terms of the variation of the Mulliken gross charges (qi) of an atom in a molecule, which is accompanied with a change in the total number of electrons (N) in this molecule: fi+ = qi(N + 1) - qi(N); fi- = qi(N) - qi(N-1) and f1° = 1/2[qi(N + 1) - qi(N - 1)]. © 1986 American Chemical Society.
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