Formation and Reaction of Br2-Radicals in the Ionic Liquid Methyltributylammonium Gis(trifluoromethylsufonyl)imide and in Other Solvents

Published

November 1, 2002

Author(s)

J Grodkowski, Pedatsur Neta

Abstract

Reaction of solvated electrons with BrCh₂Ch₂Br produces Br^- and CH₂CH₂Br, which decomposes rapidly into CH₂=CH₂ and Br with Br₂ ^-. The stability of Br₂ ^- is much greater in the ionic liquid and in acetonitrile than in water or alcohols. The rate constant for oxidation of chlorpromazine by Br₂ ^- radicals decreases upon changing the solvent from water (nearly equal to} 6 x 10⁹ L mol^-1 s^-1) to methanol (2.8 X 10⁹ L mol^-1 S^-1), ethanol (1.2 x 10⁹ L mol^-1 s^-1), 2 propanol (1.2 x 10⁹ L mol^-1 s^-1), N-propanol (7.5 x 10⁸ L mol^-1 s^-1), tert-butyl alcohol (3.0 x 10⁸ L mol^-1 s^-1), acetonitrile (2.0 x 10⁷ L mol^-1), N, N-dimethylformamide (5.3 x 10⁶ L mol^-1 s^-1), the ionic liquid methyltributylammonium bis(trifluoromethylsulfonyl)imide (1,1 x 10⁶ L mol^-1 s^-1), and hexamethylphosphoramide (less then} 8 x 10⁴ L mol^-1 s^-1). The rate constants show poor correlation with typical solvent polarity parameters but reasonable correlations with hydrogen bond donor acidity and with anion-solvation tendency parameters. From the good correlation with the free energy of transfer of Br^- ions from water to the various solvents it is suggested that the change in the energy of solvation of Br^- in the different solvent is the main factor that affects the rate constant of the reaction through its effect on the reduction potential of Br₂ ^- and the driving force of the reaction.

Citation

Journal of Physical Chemistry A

Volume

106

Issue

No. 46

Pub Type

Journals

Keywords

electron transfer, ionic liquids, pulse radiolysis, reaction kinetics, solvent effect

Citation

Grodkowski, J. and Neta, P. (2002), Formation and Reaction of Br₂^-Radicals in the Ionic Liquid Methyltributylammonium Gis(trifluoromethylsufonyl)imide and in Other Solvents, Journal of Physical Chemistry A (Accessed December 6, 2024)