The recent analysis of the composition of the frozen surface of comet 67P/Churyumov-Gerasimenko has revealed a significant number of complex organic molecules. Methyl isocyanate (CH 3 NCO) is one of the more abundant species detected on the comet surface. In this work we report extensive characterization of its rotational spectrum resulting in a list of 1269 confidently assigned laboratory lines and its detection in space towards the Orion clouds where 399 lines of the molecule have been unambiguously identified. We find that the limited mm-wave laboratory data reported prior to our work require some revision. The abundance of CH 3 NCO in Orion is only a factor of ten below those of HNCO and CH 3 CN. Unlike the molecular abundances in the coma of comets, which correlate with those of warm molecular clouds, molecular abundances in the gas phase in Orion are only weakly correlated with those measured on the comet surface. We also compare our abundances with those derived recently for this molecule towards Sgr B2 (Halfen et al. 2015, ApJ, 812, L5). A more accurate abundance of CH 3 NCO is provided for this cloud based on our extensive laboratory work.

New laboratory data of ethyl mercaptan, CH 3 CH 2 SH, in the millimeter and submillimeter-wave domains (up to 880 GHz) provided very precise values of the spectroscopic constants that allowed the detection of gauche-CH 3 CH 2 SH towards -2 -Orion KL. 77 unblended or slightly blended lines plus no missing transitions in the range 80 -280 GHz support this identification. A detection of methyl mercaptan, CH 3 SH, in the spectral survey of Orion KL is reported as well. Our column density results indicate that methyl mercaptan is ≃ 5 times more abundant than ethyl mercaptan in the hot core of Orion KL.1 This work was based on observations carried out with the IRAM 30-meter telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). 3 Hollis, J. M.; Remijan, A. J.; Jewell, P. R.; Lovas, F. J.; Corby, J. F.

We report on the tentative detection of trans ethyl methyl ether (tEME), t-CH 3 CH 2 OCH 3 , through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for gauche-trans-n-propanol, Gt-n-CH 3 CH 2 CH 2 OH, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30 m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are ≤(4.0 ± 0.8) × 10 15 cm −2 and ≤(1.0 ± 0.2) × 10 15 cm −2 for tEME and Gt-n-propanol, respectively. The rotational temperature is ∼100 K for both molecules. We also provide maps of CH 3 OCOH, CH 3 CH 2 OCOH, CH 3 OCH 3 , CH 3 OH, and CH 3 CH 2 OH to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio N(CH 3 OCH 3 )/N(tEME) ≥ 150 in the compact ridge of Orion.

Context. Peptide-like bond molecules, which can take part in the formation of proteins in a primitive Earth environment, have been detected only towards a few hot cores and hot corinos up to now. Aims. We present a study of HNCO, HC(O)NH2, CH3NCO, CH3C(O)NH2, CH3NHCHO, CH3CH2NCO, NH2C(O)NH2, NH2C(O)CN, and HOCH2C(O)NH2 towards the hot core G31.41+0.31. The aim of this work is to study these species together to allow a consistent study among them. Methods. We have used the spectrum obtained from the ALMA 3 mm spectral survey GUAPOS, with a spectral resolution of ~0.488 MHz (~1.3–1.7 km s−1) and an angular resolution of 1.′′2 × 1.′′2 (~4500 au), to derive column densities of all the molecular species presented in this work, together with 0.′′2 × 0.′′2 (~750 au) ALMA observations from another project to study the morphology of HNCO, HC(O)NH2, and CH3C(O)NH2. Results. We have detected HNCO, HC(O)NH2, CH3NCO, CH3C(O)NH2, and CH3NHCHO, but no CH3CH2NCO, NH2C(O)NH2, NH2C(O)CN, or HOCH2C(O)NH2. This is the first time that these molecules have been detected all together outside the Galactic centre. We have obtained molecular fractional abundances with respect to H2 from 10−7 down to a few 10−9 and abundances with respect to CH3OH from 10−3 to ~4 × 10−2, and their emission is found to be compact (~2′′, i.e. ~7500 au). From the comparison with other sources, we find that regions in an earlier stage of evolution, such as pre-stellar cores, show abundances at least two orders of magnitude lower than those in hot cores, hot corinos, or shocked regions. Moreover, molecular abundance ratios towards different sources are found to be consistent between them within ~1 order of magnitude, regardless of the physical properties (e.g. different masses and luminosities), or the source position throughout the Galaxy. Correlations have also been found between HNCO and HC(O)NH2 as well as CH3NCO and HNCO abundances, and for the first time between CH3NCO and HC(O)NH2, CH3C(O)NH2 and HNCO, and CH3C(O)NH2 and HC(O)NH2 abundances. These results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas phase through thermal desorption or shock-triggered desorption.