Solvent effects on the reaction rate depend on both the nature of the solvent and the type of reaction occurring, and thus can be challenging to apply systematically. It is helpful to consider previous work in this field in order to understand and ultimately generalize solvent effects. In Figure , it is assumed that the solvent does not participate in the reaction via atom bonding or transfer, and only provides electrostatic interactions which modify the solution phase energy of the reactants, transition state, and products. In reality, there are situations where the solvent does participate, thus changing the reaction mechanism; for example, Liang et al. show that water can assist a 1,2 hydrogen shift step in a cycloaddition mechanism to form heterocycles . While consideration of these alternative steps are important in determining overall reaction mechanism and kinetics, we will mainly consider those cases in which the solvent does not participate in the reaction, to simplify the goal of generalizing the effect solvation has on gas phase rates.