How the addition of atomic hydrogen to a multiple bond can be catalyzed by water molecules.

Observational data show complex organic molecules in the interstellar medium (ISM). Hydrogenation of small unsaturated carbon double bond could be one way for molecular complexification. It is important to understand how such reactivity occurs in the very cold and low-pressure ISM.

The significant role of water in reactions occurring on the surface of interstellar ice grains: Hydrogenation of pure ketene HCCO ice hydrogenation of mixed HCCO/HO ice at 10 K.

Water ice plays an important role in reactions taking place on the surface of interstellar ice grains, ranging from catalytic effects that reduce reaction barrier heights to effects that stabilize the reaction products and intermediates formed, or that favor one reaction pathway over another, passing through water-involvement in the reaction to produce more complex molecules that cannot be formed without water or water-derived fragments H, O and OH. In this context, we have combined experimental and theoretical studies to investigate ketene (CHCO) + H solid-state reaction at 10 K in the presence and absence of water molecules under interstellar conditions, through H-bombardment of CHCO and CHCO/HO ices. We show in the present study that with or without water, the ketene molecule reacts with H atoms to form four reaction products, namely CO, HCO, CH and CHCHO.

Conformational preference analysis in CH using orbital forces and non-covalent interactions; comparison with related systems.

Dynamic Orbital Forces (DOF) and Non-Covalent Interactions (NCIs) are used to analyze the attractive/repulsive interactions responsible of the conformational preference of ethane and some related compounds. In ethane, it is found that the stabilization of the staggered conformation with respect to the adiabatic eclipsed one arises from both attractive and repulsive interactions in CH⋯CH. Attractive ones are predominant in a ratio 2 : 1, with an important role of a σ MO.

Formation of CO, CH, HCO and CHCHO through the HCCO + H surface reaction under interstellar conditions.

The reaction of ketene (HCCO) with hydrogen atoms has been studied under interstellar conditions through two different experimental methods, occurring on the surface and in the bulk of HCCO ice. We show that ketene interaction with H-atoms at 10 K leads mainly to four reaction products, carbon monoxide (CO), methane (CH), formaldehyde (HCO) and acetaldehyde (CHCHO). A part of these results shows a chemical link between a simple organic molecule such as HCCO and a complex one such as CHCHO, through H-addition reactions taking place in dense molecular clouds.

Orbital energies and nuclear forces in DFT: Interpretation and validation.

The bonding and antibonding character of individual molecular orbitals has been previously shown to be related to their orbital energy derivatives with respect to nuclear coordinates, known as dynamical orbital forces. Albeit usually derived from Koopmans' theorem, in this work we show a more general derivation from conceptual DFT, which justifies application in a broader context. The consistency of the approach is validated numerically for valence orbitals in Kohn-Sham DFT.