Local softness and chemical reactivity in the molecules CO, SCN^- and H2CO

Fukui functions (softnesses) are calculated for three species - formaldehyde, the thiocyanate ion and carbon monoxide. The fukui function for a molecule has been defined as the derivative of electron density with respect to the change of number of electrons, keeping the positions of nuclei unchanged; this differentiation is performed by finite difference. Local softness and fukui function are proportional. The calculated results, expressed in terms of contour maps and condensed values of fukui functions, substantiate the previous argument that fukui functions serve as reactivity indices for chemical reactions. Particularly, it is confirmed that: (1) a nucleophilic reagent approaches the carbon atom in formaldehyde from the direction perpendicular to the molecular plane, while an electrophilic reagent approaches the oxygen atom in the molecular plane; (2) the sulphur end is softer than the nitrogen end in the thiocyanate ion; and (3) carbon monoxide behaves like a Lewis acid in bonding with transition metals. © 1988.

Duke Scholars

Author Weitao Yang Chemistry