Bond Localization Effects

This arises because as the temperature in increased from ambient, the main initial effect is to loosen the hydrogen-bonded local stmcture that iitiribits reorientation. Flowever, at higher temperatures, the themial motion of the water molecules becomes so marked that cluster fomration becomes iitiiibited. 

With regard to the composition of the electrical effect, examination of the p values reported in Table XVII shows that in six of the sets which gave significant correlation, the localized effect is predominant (in these sets, either Pr < 50 or / is not significant). Thus it would appear that in so far as substituent effects are concerned, there are two major classes of electrophilic addition to the carbon-carbon double bond predominance of the localized effect or predominance of the delocalized effect. This behavior may well be accounted for in terms of the reaction mechanism. The rate-determining step in the electrophilic addition reaction is believed to be the formation of an intermediate which may be either bridged or a free carbonium ion. 

Figures 3a and 3a depict the weak bond of an O2 molecule with the lattice. It is formed by an electron being drawn from an ion of the lattice to an O2 molecule. Owing to the greater electron aflSnity of the O2 molecule, the electron may be considered completely transferred from the lattice to the molecule as a result, a molecular ion 02 is formed and a localized hole appears in the lattice attached to the ion Oi, The entire system (the adsorbed O2 molecule + adsorption center) acquires a noticeable dipole moment with negative pole directed outward, but remains electrically neutral as a whole. The bond is effected without the participation of a free lattice electron. The transition to a strong acceptor bond entails the localization of an electron, or, what amounts to the same thing, the delocalization of a hole. Such a strong acceptor bond is depicted in Figs. 3b and 3b. ...

Advances in spectroscopic and crystallographic techniques, and in computational methods, have allowed for detailed physical and theoretical analyses of the cycloproparenes. Central to a consideration of this interesting class of compounds is their role in debate over the Mills-Nixon effect—the concept of bond localization within the aromatic ring. 

The experimental crystal structure determination showed that this molecule has bond distances with unexpected values, which were not consistent with classically localized bond-valence forms in particular, the C-9=N-4 and C-12=N-6 bonds, which are both formally double bonds, and not of equal length. In addition, the N-l-N-2, N-3-N-4, and N-5-N-6 bonds were expected to be shorter than the C-N single bonds, C-l-N-3, C-2-N-3, and C-ll-N-5. In fact, none of the former three is shorter than any other of the latter three. They are shorter than the C-12-C-10 bond in the ring system. The bond distances in C-ll-S-l-C-1 fragment are normal for their types. These two C-S bonds have effectively ideal lengths and are in the normal range. 

Morita, T. Bond localization and the hyperconjugative effect in the aromatic car-bonium ions. I. Bull. Chem. Soc. Japan 32, 893 (1960a). 

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