Carbodiimide production from cyanamide by UV irradiation and thermal reaction on amorphous water ice

Cyanamide (NH2CN), an interstellar molecule, is a relevant molecule in prebiotic chemistry, because it can be converted into urea in liquid water. Carbodiimide (HNCNH) the most stable cyanamide isomer. is able to assemble amino acids into peptides. In this work, using FTIR spectroscopy, we show that carbodiimide can be formed from cyanamide at low temperature (10 K), by a photochemical process in argon matrix, in water matrix, or in solid film. We also report experimental evidence about the carbodiimide formation when cyanamide is condensed at low temperature (50-140 K) on an amorphous water ice surface, or when it is trapped in the water ice. The water ice acts as a catalyst. This isomerization reaction occurs at low temperature 14 (T < 100 K), which agrees with those expected in the interstellar clouds composed of dust grains in which water is the most predominant compound. Finally, the hydrolysis reaction of cyanamide or carbodiimide leading to urea or isourea formation is not observed under our experimental conditions.