External field effects and chemical reactivity

Sanfeld et al. (1990) have theoretically analysed the competition between chemical reactions at the surface and in the volume. They define a surface elasticity which is determined by the kinetics of all these processes and conclude that the effect of capillary forces may be considered as an external field acting on the reactive system. Their conception started from the principle of De Donder, as did our general description of relaxation in chemical reactions. To generalise relaxation phenomena at interfaces can be described as ordinary chemical reactions. In principle there is no distinction between the application of the laws to chemical kinetics in bulk phases and at interfaces. 

This chapter is intended to provide basic understanding and application of the effect of electric field on the reactivity descriptors. Section 25.2 will focus on the definitions of reactivity descriptors used to understand the chemical reactivity, along with the local hard-soft acid-base (HSAB) semiquantitative model for calculating interaction energy. In Section 25.3, we will discuss specifically the theory behind the effects of external electric field on reactivity descriptors. Some numerical results will be presented in Section 25.4. Along with that in Section 25.5, we would like to discuss the work describing the effect of other perturbation parameters. In Section 25.6, we would present our conclusions and prospects. 

The effect of external field on reactivity descriptors has been of recent interest. Since the basic reactivity descriptors are derivatives of energy and electron density with respect to the number of electrons, the effect of external field on these descriptors can be understood by the perturbative analysis of energy and electron density with respect to number of electrons and external field. Such an analysis has been done by Senet [22] and Fuentealba [23]. Senet discussed perturbation of these quantities with respect to general local external potential. It can be shown that since p(r) = 8E/8vexl, Fukui function can be seen either as a derivative of chemical potential... 

The asymmetry of distributions of positive and negative charges in a molecule can have important effects on its physical properties as well as on its chemical reactivity. This asymmetry can have two quite different origins, illustrated by the permanent and induced dipole moments. A molecule such as HF has a permanent dipole moment which results from the electronegativities of the H and F atoms but even a symmetrical molecule such as H2C=CH2 can acquire an induced dipole moment in an external electric field. 

---