Solvent types

Solvents are generally categorized into one of three categories:

  • Protic solvents contain an OH, NH or other labile hydrogen (H+ proton)
  • Aprotic solvents do not contain any labile protons
  • Polar solvents have large dipole moments (aka partial charges). They contain bonds between atoms with large differences in electronegativity, like oxygen and hydrogen.

Solvents are chosen carefully for their compatibility with specific reactions. For example, polar solvents are able to dissolve many reagents easily, but can have high boiling points, making them trickier to remove from reaction products.

Protic solvents are able to stabilize charged intermediates but their ability to hydrogen bond with charged species can solvate or create a solvent shell around reactive species, hindering the rate of some reactions. Aprotic solvents are a good choice when designing a reaction where the rate-determining step relies on the interaction of highly charged reactive species.