Collision theory for reactions in solution

Gas phase collision formulae (Section 4.1.2) can be used for many reactions in solution, i.e. for those involving uncharged species forming activated complexes with little or no charge separation. The theory of such reactions will not be considered further, and it will be assumed that the gas phase treatment is adequate. 

However, modifications are required for reactions involving ions and charged or charge-separated activated complexes (Problem 4.5(ii) and Tables 7.1 to 7.3). 

These effects of charge and solvent are quantified by an exponential energy term related to the electrostatic interactions between the ions. 

For this reason, transition state theory (see Section 7.3) is a more direct and straightforward way to give a theoretical discussion of the effect of charge and solvent on rates. 

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