Stability of [MeBu3N][Tf2N] under gamma irradiation

Abstract

The stability of the ionic liquid [MeBu₃N][Tf₂N], dry or after contact with water (where [MeBu₃N]⁺ is the methyltributylammonium cation and [Tf₂N]⁻ is the bistriflimide anion), was studied under ¹³⁷Cs gamma irradiation in argon and in air. In a quantitative study with an absorbed dose of 2 MGy this ionic liquid was highly stable regardless of the radiolysis conditions. The radiolytic disappearance yields determined by ESI-MS were −0.38 and −0.25 µmol J⁻¹ for the cation and anion, respectively. ESI-MS, NMR, and liquid chromatography coupled with ESI-MS identified a large number of degradation products in very small quantities for the same dose. The cation radicals were formed by the loss of a Bu˙ group, the Me˙ group, or two H˙ atoms to form a double bond with the butyl chain. Radiolysis of the anion produced mainly F˙ and CF₃˙ radicals. The anion radicals recombined with the cation to form a wide range of secondary degradation products regardless of the radiolysis conditions.