Glycine radicals in the gas phase†‡

Abstract

2-Glycyl radical (1), 2-glycyl methyl ester (2), and 2-glycyl N-methylamide radicals (3) were generated in the gas phase by collisional neutralization of the corresponding cations and studied by neutralization–reionization (NR) mass spectrometry and ab initio and density functional theory calculations. Stable fractions were found for 1–3 that did not dissociate on the 4 µs timescale of the experiment. The major unimolecular dissociations observed were cleavages of the CO–X bonds (X = OH, OCH₃, and NHCH₃) to form aminoketene, and cleavages of the C–CO bond to form aminocarbene, which gave rise to prominent fragments in the NR mass spectra. In addition, hydrogen rearrangements occurred in 1–3 and an unusual methyl migration took place in 3. G2(MP2) bond dissociation energies are reported for 1 and 1⁺. Combined B3LYP and PMP2/6-311+G(2df,p) calculations were used to provide bond dissociation energies for 2, 2⁺, 3 and 3⁺.