| Abstract
| - Both theoretical and experimental studies are reported for the gas-phase reactions of protonatedhydroxylamine with acetic and propanoic acids which yield protonated glycine and alanine, GlyH+ andAlaH+, respectively. The key step for these reactions is an insertion of the amino group into a C−H bond.For the formation of AlaH+, the reaction barrier for insertion into a Cβ−H bond is ca. 5 kcal·mol-1 lowerthan that for the insertion into a Cα−H bond; the product β-AlaH+ is ca. 6 kcal mol-1 lower in energy thanα-AlaH+. Thus, both kinetics and thermodynamics favor formation of the β-form. The energetic preferencefor the β-form is due to more efficient hydrogen bonding between the amino group and the carbonyl oxygenin the limiting transition structure and in the β-AlaH+ product. These theoretical results are in excellentaccord with selected ion flow tube measurements of the gas-phase synthesis which show striking specificityfor the β-isomer according to multi-collision-induced dissociation of the AlaH+ product ion. The results suggestthat Gly and β-Ala found in carbonaceous chondrite meteorites are products of interstellar chemistry.
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