Non-Bonding Electron Polarization

According to Anderson [29], bond order loss causes a localization of electrons. The bond contraction raises the local density of electrons in the core bands and electrons shared in the bonds. The core band will shift accordingly as the potential well deepens (called entrapment, T). The densification and entrapment of the core and bonding electrons in turn polarize the non-bonding electrons, raising their energy closer to Ejs. The polarize electrons will split and screen the potential. 

This sequential happening of bond contraction, densification, entrapment, and polarization (bonding-non-bonding electron repulsion and strong correlation) may elaborate the Strong locahzation of Anderson for systems with bond order loss [2]. 

At the terminating end of a solid, the characteristics of the non-bonding states become even more pronounced. Polarization occurs to the lone electrons, if exist, by the densely trapped bonding and core electrons of the undercoordinated atoms, as illustrated in Fig. 11.5. 

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Local densification and quantum entrapment of energy and electrons take places, of which the extent increases with the lowering of atomic CN. Polarization happens to the non-bonding electrons (non-bonding electron polarization, NEP) by the densely entrapped core and bonding electrons, which exemplifies Anderson s localization due to bond order deficiency. 

Non-Bonding Electron Polarization 11.3.1 Attributes of Non-Bonding Electrons... 

Size emergency Emerging properties that the bulk parent never demonstrate (non-bonding electron polarization) ... 

Broken-bond-induced local strain and the associated quantum entrapment and non-bonding electron polarization dictate skin and defect mechanics. 

Cooperative relaxation of the H-bond in length and energy and the associated binding electron entrapment and non-bonding electron polarization determine the... 

Correlation of Detectable Quantities 33.3.1 Non-Bonding Electron Polarization... 

In this model, one considers the acetals to be composed of polarizable dipolar moieties that can be stabilized by electron transfer from an electron-rich moiety (non-bonding electron on oxygen low ionisation energy) to adjacent polar and polarizable moieties (high electron affinity). A strong overlap between n(O) and cr c 0 orbitals optimizes this electronic transfer. As these orbitals are not spherical, n(0)/ct c o overlap depends on... 

There is no direct experimental evidence to show the importance of the secondary electronic effects in the ester function except for the relative stability of the Z over the form. However, the relative stability of the different forms of dialkoxycarbonium ions can be explained by considering these electronic effects. Since dialkoxycarbonium ions are alkylated derivatives of esters, the result can be used as evidence to support the importance of the secondary electronic effects in the ester function. It is known from X-ray evidence and supported by calculations (8, 9) that dialkoxycarbonium ions like esters are planar and that they can exist theoretically in three different forms, the ZZ ( 0), the EZ (VO, and the EE (12) forms. The two oxygens of 10 each have one non-bonded electron pair antiperiplanar to a polar C-0 bond, 0 has one, whereas 2 has none. Thus, 10, 11, and 12 have respectively two, one and zero secondary electronic effects, and on that basis, their relative stability should follow in this order. In the ZZ form ( ] 0), there is a severe steric repulsion between the two R groups thus, with the exception of cases where the two R groups are part of a ring, this form must be eliminated. The EZ form (VO must therefore represent the most stable form of dialkoxycarbonium ions. 

The above results are consistent with a molecular model of adsorption that assumes liaison of substituent Z of Z(CH2) H sorbates with the phenyl group of poly(Sty-co-DVB) absorbents. When Z is a halogen atom, this liaison is postulated to involve the non-bonded electrons on Z with the pi-electrons of a phenyl group as indicated in Fig. 37a (when the adsorbed molecule is represented by ZCRR R") and in Fig. 37b (when ZCRR R" is Z(CH2)nH). The order observed for a0 (Eq. 30) as a function of Z is consistent with the assumption that the inherent dynamic adsorption density of such molecules on the adsorption site (in this case the phenyl groups of the polymer) varies with the polarity and polarizability of substituent Z, and inversely with the bulkiness of that substituent. 

The total electron density of a molecule is also not very sensitive to the neglect of bond interaction. Hence, the polarity of molecules can be reasonably interpreted in terms of localized bond functions. For example, except for the polarization effects mentioned before (page 173), the molecular dipole moment of NH3 can be interpreted in terms of the localized NH functions describing polar bonds plus the contribution of a non-bonding electron pair occupying a hybrid orbital of N ... 

The reactivity of carboxylic acids and their derivatives is a result of polar bonds, non-bonding electron pairs and the carbon-oxygen double bond. The C=0 can attract both nucleophiles and electrophiles. 

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