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