Electron attachment to the N-substituted amino acids N-methylglycine and N-methylalanine: Effective cleavage of the N–Cα bond at sub-excitation energies

Dissociative electron attachment to gas phase N-methylglycine and N-methylalanine is studied by means of a crossed beams apparatus. Effective cleavage of the N–Cα bond is observed within a low energy resonance peaking at 1.8 eV in both compounds and observable via the appearance of the fragment CH2COOH− from N-methylglycine and CH(CH3)COOH− from N-methylalanine. In glycine and alanine cleavage of the N–Cα bond was only observed as a weak reaction in combination with hydrogen transfer. As for previously studied amino acids, the most dominant anionic fragment is due to the loss of hydrogen atom from the respective target molecule resulting in the formation of the closed shell dehydrogenated parent anion (M–H)−.