Illustrated Glossary of Organic Chemistry

Dielectric constant (ε): A measure of a substance's ability to insulate charges from each other. Taken as a measure of solvent polarity, higher ε means higher polarity, and greater ability to stabilize charges. Not the same as dipole moment.

Water (ε = 80) High polarity Polar solvent		Dichloromethane (ε = 9.1) Low polarity Nonpolar solvent

Dielectric Constants of Common Solvents

Polar solvents (ε > 20)

Water ε = 80		Dimethylsulfoxide (DMSO) ε = 49		N,N-Dimethylformamide (DMF) ε = 37		Methanol ε = 33		Ethanol ε = 25		Acetone (propanone) ε = 21

Nonpolar solvents (ε < 20)

Dichloromethane ε = 9.1		Tetrahydrofuran (THF) ε = 7.6		Acetic acid (HOAc) ε = 6.2		Diethyl ether (ether) ε = 4.3		Hexane ε = 1.9