Electron spin resonance spectra and structure of the radical cations of 1,3-dichloropropane and other dichloroalkanes

Abstract

Exposure of a dilute solution of 1,3-dichloropropane in Freon to X-rays at 77 K gave e.s.r. spectra composed of many lines, which are attributable to hyperfine coupling to two equivalent chlorine nuclei and two equivalent protons in the corresponding cation. Similar experiments with methylsubstituted compounds revealed that the two equivalent protons can be assigned to one of the, protons in each terminal methylene group. CNDO/2 calculations for the radical cation suggest that reasonable values for the coupling constants of these two protons are obtained for a specific nonplanar cyclic structure having a Cl–Cl three-electron bond (σ₁²σ₂¹). E.s.r. spectra were also studied for the radical cations of other dichloroalkanes, Cl(CH₂)_nCl. For n= 1, 2, 4, and 5, these also gave spectra indicating a SOMO on two equivalent chlorine nuclei.