First detection of C₂H₅NCO in the ISM and search of other isocyanates towards the G+0.693-0.027 molecular cloud

Little is known about the chemistry of isocyanates (compounds with functional group R-N=C=O) in interstellar medium, as only four them have been detected so far: isocyanate radical (NCO), isocyanic acid (HNCO), N-protonated (H$_2$NCO$^+$) and methyl (CH$_3$NCO). The molecular cloud G+0.693-0.027, located Galactic Centre, represents an excellent candidate to search for new since it exhibits high abundances simplest ones, HNCO CH$_3$NCO. After CH$_3$NCO, next complex are ethyl (C$_2$H$_5$NCO) vinyl (C$_2$H$_3$NCO). Their detection ISM would enhance our understanding formation these compounds space. We C$_2$H$_5$NCO H$_2$NCO$^+$ towards G+0.693-0.027 (the former first time medium) (4.7$-$7.3)$\times$10$^{-11}$ (1.0$-$1.5)$\times$10$^{-11}$, respectively. A ratio CH$_3$NCO / = 8$\pm$1 obtained; therefore relative abundance determined HNCO:CH$_3$NCO:C$_2$H$_5$NCO 1:1/55:1/447, which implies a decrease by more than one order magnitude going progressively from C$_2$H$_5$NCO. This similar what has found e.g. alcohols thiols suggests that likely formed on surface dust grains. In addition, we obtained column density ratios NCO > 269, $\sim$ 2100 C$_2$H$_3$NCO C$_2$H$_5$NCO~<~4. comparison Methyl~/~Ethyl (-NCO), (-OH), formiates (HCOO-), nitriles (-CN) (-SH) performed shows ethyl-derivatives may be efficiently N-bearing molecules O- S-bearing molecules.