Intrinsic barrier polarizability

CH=NH,118 CH=S,118 CH=OH,120 and N02H.117 The most comprehensive study which also incorporates results form earlier work is that by Bernasconi and Wenzel118 the present discussion is largely based on this paper and on references 113, 117, and 120. A major conclusion is that even though the intrinsic barriers of these gas phase reactions depend on the same factors as solution phase proton transfers such as resonance, polar, and polarizability effects, the relative importance of these factors is quite different in the gas phase, and electrostatic effects involving the proton-in-flight constitute an important additional factor. 

One application of PI-QTST to PT has been to study a model A-H-A PT solute in a polar solvent [77]. This computational study provided a detailed examination of the specific features of PT, including the competition between proton tunneling and solvent activation, the influence from intramolecular vibrational modulation of the PT barrier, and the role of electronic polarizability of both the solute and the solvent. Changes in the total quantum activation free energy, and hence the reaction probability, due to these different effects were calculated (cf. Fig. 18). By virtue of these studies, it was found that to fully understand the rate of a given PT reaction, one must deal with a number of complex, nonlinear interactions. Examples of such interactions include the nonlinear dependence of the solute dipole on the position of the proton, the coupling of the solute dipole to both the proton coordinate and to other vibrational modes, and the intrinsically nonlinear interactions arising from both solute and solvent polarizability effects. Perhaps the most important conclusion... 

---