Radical addition and H abstraction reactions in C₂H₂, C₂H₄, and C₂H₆: A gateway for ethyl- and vinyl-bearing molecules in the interstellar medium

Context. Recent interstellar detections include a significant number of molecules containing vinyl (C 2 H 3 ) and ethyl 5 groups in their structure. For several these molecules, there is no clear experimental or theoretical evidence that supports formation from simpler precursors. Aims. We carried out systematic search viable reactions starting closed-shell hydrocarbons two carbon atoms (ethane, C 6 ; ethylene, 4 acetylene, ), with the goal determining chemical routes for on top dust grains. Methods. used density functional theory calculations combination semiclassical instantem to derive rate coefficients radical-neutral surface reactions. The effect was modeled through an implicit approach, profiting weak interaction between considered surfaces. Results. Our results show both OH radicals are key converting acetylene ethylene into more complex liable continue reacting form organic molecules. relevant reactions, example additions, present constants above 10 1 s ?1 likely competitive diffusion Similarly, atom addition very fast process, all cases, greatly enhanced by quantum tunneling. Hydrogen abstraction less relevant, but may play role specific cases involving radical. Reactions other NH CH have much impact chemistry ethyl- vinyl-bearing Conclusions. effective at low temperatures four , OH, OH) our proposed mechanism opens gate indicates potential prevalence OH-bearing grain. Following suggested reaction pathway, we explain many newly detected propose new detection. reinforce recent view importance radical chemistry.