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A justification for the likely presence of negative Fukui functions in molecules with small band gaps is given, and a computational study performed to check whether molecules with small band gaps have negative Fukui functions to a chemically significant extent is reported. While regions with negative Fukui functions were observed, significantly negative values for the atom-condensed Fukui functions were not observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In our quest to explore molecules with chemically significant regions where the Fukui function is negative, we explored reactions where the frontier orbital that indicates the sites for electrophilic attack is not the highest occupied molecular orbital. The highest occupied molecular orbital (HOMO) controls the location of the regions where the Fukui function is negative, supporting the postulate that negative values of the Fukui function are associated with orbital relaxation effects and nodal surfaces of the frontier orbitals. Significant negative values for the condensed Fukui function, however, were not observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The mechanism of a chemical reaction can be characterized in terms of chemical events that take place during the reaction. These events are bond weakening/breaking and/or bond strengthening/forming. The reaction electronic flux (REF), a concept that identifies and rationalizes the electronic activity taking place along the reaction coordinate, has emerged recently as a powerful tool for characterizing the mechanism of chemical reactions. A quantitative theory introducing new descriptors for characterizing reaction mechanisms is presented in detail and three illustrative examples are revisited. In nucleophilic substitution reactions the REF indicates that bond breaking or forming events may be leading the electronic activity whereas in the methanol decomposition reaction by copper oxide, the REF allows to discover that consecutive electronic reductions of copper together with bond breaking processes control the course of the reaction. [ABSTRACT FROM AUTHOR]