Mass spectra of esters of α-hydroxy and α-methoxy acids

The most abundant fragment produced by electron bombardment of esters of the type R¹R²C(OR³)CO₂R⁴ is the R¹R²C = documentclass{article}pagestyle{empty}begin{document}$ mathop {rm O}limits^{{rm + } cdot } $end{document}R³ ion. Methyl glycollate (R¹ = R² = R³ = H, R⁴ = Me) eliminates the HCO˙ radical by a complex rearrangement involving the methylenic hydrogen atoms. The methyl and ethyl esters of methoxyacetic acid (R¹ = R² = H, R³ = Me, R⁴ = Me or Et) eliminate formaldehyde by the McLafferty rearrangement.