Solvent effects model

Development of Quantum Mechanical Solvent Effect Models—Microscopic Electrostatic Contributions. 

Solvents affect free-radical polymerization reactions in a number of different ways. Solvent can influence any of the elementary steps in the chain reaction process either chemically or physically. Some of these solvent effects are substantial, for instance, the influence of solvents on the gel effect and on the polymerization of acidic or basic monomers. In the specific case of copolymerization then solvents can influence transfer and propagation reactions via a number of different mechanisms. For some systems, such as styrene-acrylonitrile or styrene-maleic anhydride, the selection of an appropriate copolymerization model is still a matter of contention and it is likely that complicated copolymerization models, incorporating a number of different phenomena, are required to explain all experimental data. In any case, it does not appear that a single solvent effects model is capable of explaining the effect of solvents in all copolymerization systems, and model discrimination should thus be performed on a case-by-case basis. 

Gogonea V (1996) An approach to solvent effect modelling by the combined scaled-particle theory and dielectric continuum-medium method, Ph.D. thesis, Toyohashi University of Technology, Japan... 

Similarly to the use of other physico-chemical parameters in characterizing the solvent effect, models based on an electrostatic approach have been produced for the description of the solvent dependence of the absorption spectrum these models describe the shifts of the absorption bands in terms of the relative permittivity and refractive index of the solvent [Oo 54, Ba 54], These have fairly limited validity, however, since specific coordinative interactions cannot be neglected when considering the factors that determine the stabilities of solvates. 

Cl/ PHBA carboxyl/ and PNP C4 are reproduced qualitatively by the continuum solvent effect model/ while those for corresponding para carbons( BA C4/ PHBA C4/ and PNP Cl ) are not. The main reason for... 

The trends of the a-CD complexation-induced shifts for the ptotonated carbons, i.e., C2 auid C3, of each guest compoiind, are also not always reproducible by the continuum solvent effect model. Since the hydrogen atoms bonded to these carbons ceui contact with a-CD s H-3 euid H-5 located inside the cavity in the complexed state, the steric shielding effect must also be considered for the explanation of the C-13 shifts of these carbons. 

This form of the model is for monomer—solvent complexes generally. Under the MCD model, the complexing agent C is the other monomer (Mj). As with all of the solvent effects models, variations are possible by making a different assumption as to which units can affect radical reactivity. 

However in most of the cases, mainly in polar systems, the interactions with the surroundings are not negligible. There are a wide variety of theoretical methods for taking into account the effect of environment, ranging from various solvent effect models to pseudopotential-like approaches. One cannot overview all of them, but a few selected examples will be shown in the following. 

ON THE DEVELOPMENT OF SOLVENT EFFECT MODELS METHOD DEVELOPMENT AND INITIAL APPLICATIONS ... 

---