Polar effects positive charge

Electronic point defects, displaced electrons, almost always exist in connection with atomic point defects. A purely electronic defect, the so-called self-trapped electron trapped by induced polarization in a solid, has been suggested by Landau 29) but never found. If an incoming quantum imparts enough energy to an electron of one of the atoms of a solid, the electron will be freed from the atom and can wander through the solid. If it is not to be recaptured by the radiation-produced positive ion, it must be trapped at some other point in the solid, one with an effective positive charge. This will almost always be an atomic defect, specifically a negative ion vacancy or an impurity of suitable electron affinity relative to that of the host solid. When an electron is thus removed from an atom, the vacancy in the electronic structure is termed a positive hole. Such a hole has mobility like that of an electron... 

A ferroelectric crystal is one that has an electric dipole moment even in the absence of an external electric held. This arises because the centre of positive charge in the crystal does not coincide with the centre of negative charge. The phenomenon was discovered in 1920 by J. Valasek in Rochelle salt, which is the H-bonded hydrated d-tartrate NaKC4H406.4H 0. In such compounds the dielectric constant can rise to enormous values of lO or more due to presence of a stable permanent electric polarization. Before considering the effect further, it will be helpful to recall various dehnitions and SI units ... 

When a positively charged substituent such as the trimethylam-monio group is anywhere on the ring, but most effectively when it is ortho to the leaving group, it can favorably affect the entropy of activation with anionic nucleophiles and accelerate reaction. A recent example of reagent-substituent interaction is the electrophilic substitution of 2-carboxybiphenyl, nitration (non-polar solvent) of which occurs only at the 2 -position and not the 4 -position and has been postulated to be due to the interaction of the nitronium ion with the carboxyl group. 

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