Hydrogen halide radical anions

Abstract

Exposure of Me₃NSO₃ doped with Me₃NHX (X = F, Cl, Br, or I) to ⁶⁰Co γ-rays at 77 K gives radicals whose e.s.r. spectra show hyperfine coupling to ¹H and X nuclei. These are identified as HX˙^– radical anions. The species HF˙^– has properties of normal traped hydrogen atoms, but the remainder are thought to be genuine radical anions with a σ* semi-occupied molecular orbital. The HCl˙^– and HBr˙^– radicals rotate about a specific axis normal to the σ bond at 77 K but the motion is quenched on further cooling. Possible mechanisms for the radiolytic processes are discussed. Other radicals detected during the course of the work include SO₃˙^–, Me₃N˙⁺, and H₂ĊNMe₂SO₃.