Rate Constants for Reaction of 1,2-Dimethylimidazole With Benzyl Bromide in Ionic Liquids and Organic Solvents

Published

April 1, 2004

Author(s)

A Skrzypczak, Pedatsur Neta

Abstract

The rate constant for the Menschukin reaction of 1,2-dimethylimidazole (DMI) with benzyl bromide to produce 3-benzyl-1,2-dimethylimidazolium bromide was determined in a number of ionic liquids and molecular organic solvents. The rate constants in 12 ionic liquids are in the range of (1.0 to 3.2) x 10^-3 L mol^-1 s^-1 and vary with the solvent anion in the order (CF₃SO₂)₂N^- 6^- 4^-. Variations with the solvent cation (butylmethylimidazolium, octylmethylimidazolium, butyldimethylimidazolium, octyldimethylimidazolium, butylmethylpyrrolidinium, and hexyltributylammonium) are minimal. The rate constants in the ionic liquids are comparable to those in polar aprotic molecular solvents (acetonitrile, propylene carbonate) but much higher than those in weakly polar organic solvents and in alcohols. Corelation of the rate constants with the solvatochromic parameter E_T(30) is reasonable within each group of similar solvents but very poor when all the solvents are correlated together. Better correlation is obtained for the organic solvents by using a combination of two parameters, π (dipolarity/polarizibility) and α (hydrogen bond acidity), while additional parameters such as δ (cohesive energy density) do not provide any further improvement.

Citation

International Journal of Chemical Kinetics

Volume

36

Issue

No. 4

Pub Type

Journals

Keywords

ionic liquids, Menschukin reaction, quaternization reaction, rate constants, solvent polarity

Citation

Skrzypczak, A. and Neta, P. (2004), Rate Constants for Reaction of 1,2-Dimethylimidazole With Benzyl Bromide in Ionic Liquids and Organic Solvents, International Journal of Chemical Kinetics (Accessed April 19, 2024)