Radical cations of organic carbonates, trimethyl borate and methyl nitrate. A radiation–electron spin resonance study

Abstract

Exposure of a range of dialkyl carbonates as dilute solutions in trichlorofluoromethane at 77 K gave rearranged cations in which hydrogen is transferred from carbon to the carbonyl oxygen. Similar species were obtained from the cyclic derivatives, ethylene and propylene carbonates. No evidence has been found for complex formation with solvent molecules such as occurs for methyl formate cations. For the dimethyl derivative the rearrangement appeared to occur even at ca. 4 K. For trimethyl borate a similar reaction occurred, giving either H₂ĊOB(OMe)([graphic omitted])⁺or H₂ĊOB(OMe)+ MeOH. However, methyl nitrate gave ^˙NO₂H⁺ radicals, thought to be derived from H₂ĊONO₂H⁺. These results are compared with those for ester and lactone cations and also with those for trimethyl phosphate and dimethyl sulphate cations.