A majority of chemical reactions are carried out in solution. The use of a solvent
as reaction medium makes it easy to control reaction conditions such as tempera￾ture, pressure, pH, rate of mass transfer, and concentration of reactant. Water is
the most popular solvent. However, by using appropriate non-aqueous solvents,
substances that are insoluble in water can be dissolved, substances that are un￾stable in water remain stable, and chemical reactions that are impossible in water
become possible. The reaction environments are markedly wider in non-aqueous
solvents than in water.