Reactions between Neutral Molecules and Ions

Numerous organic reactions are of the ion-dipole type, as, for example, the Sn2 reactions given in Eqs. (5-17) and (5-18) in Section 5.3.1. Considering the reaction between an ion A of charge za and a neutral, dipolar molecule B of dipole moment according to + B (AB) C + D, Laidler and Eyring [2, 251] obtained Eq. (5-92) for the rate constant in a medium of zero ionic strength  

A somewhat different equation relating the rate constant to the relative permittivity for a reaction A -I- B C - - D, in which the electrostatic 

For a reaction between two dipoles having no net charge, the second term disappears, and the solvent effect is given entirely by the last term Eq. (5-93) then equals Eq. (5-88) in Section 5.4.3. For a reaction between an ion and a dipole (or between two charged dipoles) both terms must be included. The simplest case is for the reaction of a monovalent, structureless ion A of charge za = 0) with a neutral molecule B 

Another derivation of the reiative permittivity dependence of in k has been made by Amis [12, 21, 244] using a Coulomb energy approach for the ion-dipole interaction. Considering the mutual potential energy between an ion A of charge za e and a dipole B of dipole moment at a distance tab leads eventually to Eq. (5-95)  

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Quantitative Theories of Solvent Effects on Reaction Rates 233 5.4.4 Reactions between Neutral Molecules and Ions... 

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