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Acetamide, a small organic compound containing a peptide bond, was observed in the interstellar medium, but reaction pathways leading to the formation of this prebiotic molecule remain uncertain. We investigated the possible formation of a peptide-like bond from the reaction between acetic acid (CH3-COOH) and methylamine (CH3-NH2) that were identified in the interstellar medium. From an experimental point of view, a quadrupole/octopole/quadrupole mass spectrometer was used in combination with synchrotron radiation as a tunable source of VUV photons for monitoring the reactivity of selected ions. Acetic acid was photoionized, and the reactivity of CH3COOH+• as well as COOH+ (produced from either acetic acid or formic acid) ions with neutral CH3NH2 was further studied. With no surprise, charge transfer, proton transfer, and concomitant dissociation processes were found to largely dominate the reactivity. However, a C(O)-N bond formation process between the two reactants was also evidenced, with a weak cross section reaction. From a theoretical point of view, results concerning reactivity and barrier heights were obtained using density functional theory, with the LC-ωPBE range-separated functional in combination with the 6-311++G(d,p) Pople basis set and are in perfect agreement with the experimental data.

Synopsis O2 + molecular ion is produced by photoionization close to threshold at SOLEIL, DESIRS beam line. By means of coincidence methods, ions are prepared in selected vibrational and electronic states (X, v=0,3,15 and a, v=3). Their reactivity with the propene in single collision regime is studied in the guided ion beam in-strument CERISES, adding ability to vary the collision energy. Absolute reaction cross section and branching ratio are recorded for the 5 most intense reactive channels, described as dissociative charge transfer. Contrasted effects of internal and collision energy are observed.

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The reactions of the CN − and C 3 N − anions with cyanoacetylene HC 3 N, of special interest for the chemistry of Titan’s upper atmosphere, have been investigated by means of FTICR mass-spectrometry. Primary ions, CN − and C 3 N − , have been produced by dissociative electron attachment (DEA) from BrCN and BrC 3 N, and prepared in a clean way before reaction. Total rate constants have been measured for both reactions at 300 K and are found to be as follows: (3.9 ± 0.5) × 10 −9 and (1.0 ± 0.2) × 10 −10 cm 3 s −1 for the reaction of HC 3 N with CN − and C 3 N − , respectively. For the CN − + HC 3 N reaction, proton transfer is found to be the only reactive channel within our detection limits. Proton transfer is also dominant for the C 3 N − + HC 3 N reaction but the resulting ionic product being identical to the primary ion C 3 N − , this process is transparent for the kinetics of the C 3 N − + HC 3 N reaction and the kinetic rate retrieved corresponds to a slow and competitive detachment pathway. Yet the nature and energetics of the neutral product(s) formed through this process remain unknown. Additional experiments using isotopic products have allowed to retrieve specific rate constants associated with the proton transfer channel in the C 3 15 N − + HC 3 N and C 3 N − + HC 3 15 N reactions and the measured rates are found to be significantly lower than for the CN − + HC 3 N system. This decrease and the evolution of reactivity when going from CN − to C 3 N − and the opening of a new detachment pathway are finally discussed.