Reactions of hydrogen atoms with solid, thin films of acetone and 2-propanol at 13 K

In the interstellar clouds, a number of oxygen-containing organic compounds such as alcohols and carbonium compounds have been observed. In order to i nvestigate the role of grain processes for the formation and destruction of these compounds, thin films of acetone and 2-propanol deposited on the cop per metal surface at 13 K were reacted with cold gas-phase H atoms (similar to 27 K). The major products from acetone were found to be methane and alc ohols (smaller than propanol). 2-propanol was not detected as a reaction pr oduct. This indicates that the disproportionation reaction is the major pro cess, but that the recombination one is minor in the reaction of H with the intermediate (CH3)(2)COH radical. The reaction of H with 2-propanol led to the formation of methane, alcohols, and acetone as major products. The dep endences of the film thickness, reaction time, and reaction temperature on the product yields were measured. It is suggested that the diffusion length of the H atoms in the 2-propanol film is longer than that in the acetone h im, and consequently greater product yields were obtained for 2-propanol th an for acetone with thicker sample films. The temperature-independent produ ct yields in the range of 13-80 K invoke the tunneling processes in the rea ctions.