Abstract The phenomena of bond alternation and bond equalisation in conjugated hydrocarbons are studied using dynamic orbital forces (DOF) which provide an index of intrinsic CC binding, with its sigma and pi components. Some linear polyenes, polyynes and cumulenes have been analysed. Dealing with linear polyenes and polyynes, it is shown that sigma bonds can be considered as weak “inverted” ones in formally multiple bonds and strong “superdirect” ones in formally single ones. This alternance in sigma bonding part…

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.

Abstract 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. Yet, there is water ice in the ISM, either as grain or as mantle around grains. Therefore, the addition of atomic hydrogen on double‐bonded carbon in a series of seven molecules have been studied and it was found that water cat…

Context . Formamide is one of the possible precursors of life because it has a bond analogous to the peptide bond. Aims . In this work, we examine the reaction pathways that lead from HCN or HNC and OH to formamide. Both HCN and HNC are present in the interstellar medium, while OH could be present in interstellar water ice, which under the effect of cosmic rays, partially decomposes into H and OH. Methods . We carried out first principles calculations. We represented the solid state either by a model of clusters o…

The reaction of ketene (H 2 CCO) with hydrogen atoms has been studied under interstellar conditions through two different experimental methods, occurring on the surface and in the bulk of H 2 CCO ice.