Specific Electron Ionization-Induced Fragmentation of Secondary Alcohol Methoxyacetates

Abstract

The electron ionization-induced fragmentations of methoxyacetates derived from various secondary aliphatic alcohols have been studied with the aid of deuteration experiments, high-resolution measurements and metastable ion analysis. It was shown that the formation of the methoxyacetic acid cation-radical or protonated methoxyacetic acid as well as α-cleavages near to the acyloxy group (processes which are characteristic for many esters) do not occur for these compounds. Unexpectedly, the elimination of methoxyacetic acid or the methoxyacetoxy radical from the molecular ions appeared to proceed to a nearly equal extent. The spectra of methoxyacetates of 2-, 3- and 4-alkanols contain peaks at m/z 89, 103 and 117 (and M −71), respectively, of a moderate intensity. Their origin was proved to be due to α-cleavages near to the methoxyacetoxy group followed by skeletal rearrangement and elimination of CO to form resonance-stabilized ions (R–CH=O⁺–CH₂–O–CH₃↔R–CH₂–O⁺=CH–O–CH₃).