Chloroform is polar with a dipole moment of 1.02 as compared to carbon tetrachloride with is nonpolar having a dipole moment of 0 [1].
The polarity of a solvent is highly dependent on its dielectric constant with high dielectric constants correlating with polar solvents and low dielectric constants correlating with nonpolar solvents [2]. In many cases a polar molecule with a large dipole moment will have a large dielectric constant and act as a polar solvent. In the case of chloroform, however, its bulky chloride groups lead to a low dielectric constant and its nonpolar solvent properties. For comparison, water has a dielectric constant of 78 and chloroform has a dielectric constant of 5 [2].
References:
[1] Connell, WD. Basic Concepts of Environmental Chemistry. CRC Press, 2005
[2] Anslyn and Dougherty. Modern Physical Organic Chemistry. University Science Books, 2006
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