Chemical reactivity criterion local

These equivalent relations for the mixed Fukui functions represent the local criterion of selection of the chemical reactivity in a system where also the spin effects are considered. 

If one takes the bond length pattern (Table 4.1) as a topological criterion for radialene-Uke character, one may find it to some extent in the geometry of coran-nulene (154). This is supported by calculations of the molecular electrostatic potential, which show five minima at the bonds exocychc to the central ring and another five at the peripheral double bonds of the six-membered rings [115]. These structural features, with rather localized double bonds, are also reflected in fullerene Cgg, which consists of three corannulene substructures. Notably, the chemical reactivity of Cgg is dominated by addition reactions at a 6-6 bond (connecting two six-membered rings) [116], and it fits into this picture that the first addition of dichlorocarbene to corannulene also occurs at a radial (6-6) C=C bond [117]. 

Keywords Bond information probes Bond localization Chemical bonds Chemical reactivity Contra-gradience criterion Covalent/ionic bond components Direct/indirect bond multiplicities Entropic bond indices Fisher information Information theory Molecular information channels Orbital... 

Whereas strained ring systems are usually reactive and often unstable, molecules which satisfy the criteria for aromaticity exhibit enhanced stability. As is evident from the structural formula of 1, the cycloproparenes set these features in juxtaposition as they are strained molecules in which a single carbon atom is fused across adjacent centres of an aromatic system. The interest of the experimentalist in strained molecules has been matched by the theoretician in the search for suitable models for developing the concepts of chemical bonding and aromaticity. The cycloproparenes have been particularly important in this regard as they meet the criterion for partial aromatic bond localization and consequent bond length alternation in the aromatic ring as proposed by Mills and Nixon in 1930, viz. la vs lb. The cation 5, anion 6 and radical 7 derived from 1, and also the ketone 8 and exocyclic methylene derivative 9, are of interest in this respect. 

In these cases, the chlorobenzenes act as electron acceptors while the benzidine molecule behaves as an electron donor. The effect of chlorine substitution on the aromaticity of the planar benzene ring of the chlorobenzene derivatives is assessed from the nucleus independent chemical shift (NICS) criterion proposed by Schleyer et al. [338]. Among the various global and local molecular descriptors, electrophilicity (m) is found to be the most appropriate reactivity parameter regarding toxicity... 

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