The knowledge of synthetic routes of complex organic molecules is still far to be fully understood. The creation of reliable models is particularly challenging. Hollis et al.Hollis, J. M.; et al., 2006, ApJ 642, 933ointed out that the observations of molecular isomers provides an excellent tool to evaluate the hypothesis of the synthetic pathways. Formamide (HC(O)NH₂) is an abundant molecule in ISM detected in 1971 in SgrB2Rubin, R. H. ; et al., 1971, ApJ 169, L39 We decided to investigate two isomers of formamide some years ago: formaldoxime and nitrosomethane, like they are interesting ISM targets. Formaldoxime is a classic asymmetrical spinning top, its spectrum does not present any identification difficulties, it has been published recentlyZou L. ; et al., 2021, A&A 649, A60 Concerning nitrosomethane, the methyl top internal rotation should be taken into account, therefore the analysis is not obvious. We have been working on the project for several years. Analysis is performed using the version of RAM36 coded which includes the treatment of the nuclear quadrupole hyperfine structureIlyushin, V.V. et al, 2010, J. Mol. Spectrosc. 259, 26 Up to now the spectroscopic studies are only available up to 40 GHz Turner P. H. et al., 1978, J. Chem. Soc., Faraday Trans. 2 74, 533 We recently recorded the spectra in Lille from 225 to 660 GHz using the bolometric detection in order to improve the signal to noise ratio. The new spectroscopic results will be presented. Its presence in ISM will also be discussed. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

In the last years the number of multi-deuterated molecules detected in the Interstellar Medium (ISM) increased substantially. These molecules are found to be more abundant than expected when taking into account the ISM deuterium abundance (D/H = 2.0 ± 0.1 × 10⁻⁵, Drozdovskaya et al.Drozdovskaya, M. N., Coudert, L. H., Margulès, L., Coutens, A., Jorgensen, J. K., Manigand, S., 2022, A&A, in pressnd references therein). In order to better understand the nature of deuterium fractionation, and the interplay of the chemistry in the gas phase and on the surface of dust grains, chemical models need to be constrained by observations of singly- and multi-deuterated molecules. Doubly deuterated acetaldehyde (CD₂HCHO) has not been detected in the ISM yet as it has been studied in the laboratory only up to 40 GHz (Turner & CoxTurner, P. H., Cox, A. P., 1976, Chem. Phys. Lett., 42, 1 Turner et al.Turner, P. H., Cox, A. P., Hardy, J. A., 1981, J. Chem. Soc., 77, 1217-1231 and hence lacks an extensive spectroscopic study, in contrast with the singly-deuterated forms CH₂DCHO and CH₃CDO that were detected towards the protostellar core IRAS16293-2422B (Coudert et al.Coudert, L. H., Margulès, L., Vastel, C., Motiyenko, R., Caux, E., Guillemin, J.-C., 2019, A&A, 624, A70. In order to allow the first detection of CD₂HCHO in the ISM, and to understand its deuterium fractionation, we are studying the rotational spectrum of CD₂HCHO in the millimetre and sub-millimeter frequency range. This work should allow us to obtain an accurate spectral catalogue for CD₂HCHO, which we will use to search for this molecule in star-forming regions.

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Drozdovskaya, M. N., Coudert, L. H., Margulès, L., Coutens, A., Jorgensen, J. K., Manigand, S., 2022, A&A, in pressa Turner, P. H., Cox, A. P., 1976, Chem. Phys. Lett., 42, 1, Turner, P. H., Cox, A. P., Hardy, J. A., 1981, J. Chem. Soc., 77, 1217-1231) Coudert, L. H., Margulès, L., Vastel, C., Motiyenko, R., Caux, E., Guillemin, J.-C., 2019, A&A, 624, A70)

Methylamine (CH₃NH₂) was among the molecules detected early by means of radio astronomy. Detected initially only toward the giant star-forming region Sagittarius B2 close to the Galactic center. Recently, vinylamine (C₂H₃NH₂) and ethylamine (C₂H₅NH₂) were detected securely and tentative, respectively, toward the cold Galactic center source G+0.693−0.03,S. Zeng et al., Astrophys. J. Lett. 920 (2021) L27.aking (CH₃)₂NH a prime target for searches in space. The microwave spectrum of dimethylamine was studied more than 50 years ago up to 45 GHz and J = 8.J. E. Wollrab and V. W. Laurie, J. Chem. Phys. 48 (1968) 5058.he spectrum displays an inversion splitting of the amino H atom of 2646 MHz, and the ¹⁴N hyperfine splitting was well resolved for transitions with J ≤ 1. The internal rotation splitting of the two equivalent methyl rotors was not resolved. Very recently, a Fourier transform microwave spectroscopic (FTMW) study (2 − 40 GHz) of secondary aminesK. J. Koziol, W. Stahl, H. V. L. Nguyen, Contribution WH19, 74th ISMS, June 21−25, 2021, Urbana-Champaign, IL, USAevealed a small internal rotation splitting of order of  ∼ 200 kHz in dimethylamine. We have studied the rotation-inversion spectrum of dimethylamine between 76 and 1091 GHz covering quantum numbers up to J = 60 and K_a = 21. Hyperfine splitting was resolved at least partly for many transitions and was treated in the analysis. The small internal rotation splitting was resolved in particular for transitions at lower frequencies or with lower quantum numbers, but was not considered thus far. The analysis was carried out with Pickett's spfit program. As the program is capable of treating internal rotation, we want to combine our data with the FTMW data.

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S. Zeng et al., Astrophys. J. Lett. 920 (2021) L27.m J. E. Wollrab and V. W. Laurie, J. Chem. Phys. 48 (1968) 5058.T K. J. Koziol, W. Stahl, H. V. L. Nguyen, Contribution WH19, 74th ISMS, June 21−25, 2021, Urbana-Champaign, IL, USAr

Cyanoacetaldehyde could be present in interstellar space or in planetary atmospheres, because of the facile hydrolysis of cyanoacetylene, which is prevalent in the interstellar medium, and found in comets and in Titan’s atmosphere. We already studied its rotation spectrum ten years agoMøllendal, H.; et al., 2012, J. Phys. Chem. A 116, 4047 The two lowest energy rotamers were studied, Rotamer I was found to be 2.9(8) kJ/mol more stable than II by relative intensity measurements. There was no major difficulties with assignment of the conformer II for the ground and the two lowest energy vibrational states. On the other hand, the analysis of the most stable conformer is not satisfactory. This is due to the existence of tunnelling effect between two equivalent configurations, which makes the analysis of the spectra tricky. The assignment is actually limited to data up to 80 GHz and with Ka < 3. It should be noted that the synthesis of cyanoacetaldehyde is not straightforward, and non negligeable amount of the precursor, isoxazole, is present in the final mixture. We re-examined the millimeter wave spectra (150-330 GHz) as our DDS spectrometer is now faster and particularly suitable for unstable species. We also have more experience with analyzing Coriolis interaction from tunnelling motion.Margulès, L.; et al., 2017, A&A 601, A50 The new spectroscopic results will be presented. Its presence in ISM will also be discussed. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

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Møllendal, H.; et al., 2012, J. Phys. Chem. A 116, 4047. Margulès, L.; et al., 2017, A&A 601, A50.

We presentWe are grateful for the support of the Deutsche Forschungsgemeinschaft and the Volkswagen foundation. The assistance of the Science and Technology Center in Ukraine is acknowledged (STCU partner project P756).he results of our new study of the torsion-rotation spectrum of the fully deuterated isotopolog of methanol (CD₃OD). The new measurements were carried out from the millimeter wave range (starting at 34.5 GHz) to the terahertz range (up to 1.1 THz) using spectrometers in Kharkiv and Köln. We extend the rotational quantum number coverage up to J_max = 50 in this work. The analysis is done using the rho axis method and the RAM36 program code, as in our earlier studies on CD₃OHV. V. Ilyushin et al., Astron. Astrophys. 658 (2022) A127nd CH₃OD. Our preliminary fits show that the v_t = 2 torsional state is affected by intervibrational interactions with non-torsional vibrational modes which propagate down through intertorsional interactions, similar to the cases of CD₃OH and CH₃OD. Taking into account the astrophysical significance of methanol and its isotopologs, we decided at this stage of the analysis to concentrate our fitting attempts on the ground and first excited torsional states of CD₃OD. We will present the status of our investigations.

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We are grateful for the support of the Deutsche Forschungsgemeinschaft and the Volkswagen foundation. The assistance of the Science and Technology Center in Ukraine is acknowledged (STCU partner project P756).t V. V. Ilyushin et al., Astron. Astrophys. 658 (2022) A127a

Methanol (CH₃OH) is known to be an important precursor of various interstellar complex organic molecules. As a monodeuterated methanol, CH₂DOH is one of the most abundant isotopologues of CH₃OH which is often used to study the deuterium fractionation of CH₃OH in interstellar medium.e.g., Jørgensen et al. 2018, A&A, 620, A170.ne of the problems regarding CH₂DOH is that its emission lines are sometimes optically thick, and thus the derivation of its abundance is very difficult and frequently unreliable. Observations of its presumably optically thin ¹³C substituted species, ¹³CH₂DOH, would give us an opportunity to overcome this issue. In this study, the rotational transitions of ¹³CH₂DOH have been measured in the millimeter wave region between 216 GHz and 264 GHz with an emission type millimeter and submillimeter-wave spectrometer, SUMIRE,Watanabe et al. 2021, PASJ, 72, 372.y using a deuterium and ¹³C enriched samples.Ohno, Oyama et al, submitted to ApJ.he absolute intensities for the a-type transitions are within 10% from their theoretical values except for perturbed lines, whereas large differences are seen in the b-type transitions. Our experimental results will contribute to identify ¹³CH₂DOH in observational spectra from respective astronomical environments, and thereby allow us to study the deuterium fractionation of CH₃OH in various sources with accurate determination of the CH₂DOH abundance.

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e.g., Jørgensen et al. 2018, A&A, 620, A170.O Watanabe et al. 2021, PASJ, 72, 372.b Ohno, Oyama et al, submitted to ApJ.T

Imines are believed to be important prebiotic molecules that lead to the synthesis of amino acids in the interstellar medium (ISM). However, only four aldimine molecules, methanimine (CH₂=NH), ethanimine (CH₃CH=NH), cyanomethanimine (NCCH=NH), and propargylimine (HCCCH=NH), have been detected so far in the ISM, resulting in a poor understanding of their interstellar chemistry. The lack of high resolution spectroscopy data, which are partially caused by the chemical instability of imines under terrestrial conditions, hinders the search for other imines. Calculations suggested that 2-propanimine ((CH₃)₂C=NH) is the most stable isomer in the group of 3-carbon imine with a molecular formula of C₃H₇N. Following the lowest energy principle, it is a good target for astronomical search. If found, it would also be the first ketenimine detected in space. The rotational spectrum of 2-propanimine is not available currently, because of its chemical instability under room temperature. In addition, the two methyl internal rotors in 2-propanimine also complicate its rotational spectrum due to internal rotation, and make the spectral assignment and analysis non-trivial. In this work, we successfully measured and assigned the millimeter-wave spectrum of 2-propanimine between 50 and 500 GHz using a cryogenic preserved fresh sample from dedicated chemical synthesis. The spectroscopic results and the search for 2-propanimine in imaging spectral line surveys of SgrB2(N) and IRAS16293-2422 performed with ALMA will be presented. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. L. Zou thanks the financial support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant agreement (H2020-MSCA-IF-2019, Project no. 894508).

Propene is among the largest saturated or nearly saturated hydrocarbons that have been detected not only toward TMC-1N. Marcelino et al., ApJ 665 (2007) L127. but also in the warmer environment of the solar-type protostellar system IRAS 16293-2422S. Manigand et al., A&A 645 (2021) A53. Isobutene, also known as 2-methylpropene, (CH₃)₂C=CH₂, is thus a promising candidate to be searched for in space.
Its rotational spectrum was studied in the microwave region to some extentH. S. Gutowsky et al., J. Mol. Spec. 147 (1991) 91-99 and references therein. In this work, we have extended the measurement up to 370 GHz employing the Cologne (Sub-)Millimeter spectrometer. The molecule has two equivalent methyl rotors. The barrier height of the tops is high enough that the internal rotation splittings could either not be resolved or occur as symmetrical triplets. A few quartets are also assigned, where splittings are up to  ∼ 10 MHz. The analysis has been carried out with the ERHAM program P. Groner, J. Chem. Phys. 107 (1997) 4483-4498.sing the previous data as well. We have accessed transitions up to J = 60 and K_c = 41, greatly improving the spectroscopic parameters for this molecule and thus paving the way to search for it in space.

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N. Marcelino et al., ApJ 665 (2007) L127., S. Manigand et al., A&A 645 (2021) A53.. H. S. Gutowsky et al., J. Mol. Spec. 147 (1991) 91-99 and references therein.. P. Groner, J. Chem. Phys. 107 (1997) 4483-4498.u

Glycolic acid (HOCH₂CO₂H) is a promising candidate for interstellar detection because it is the next step in molecular complexity from known interstellar species such as formic acid and methyl formate. Glycolic acid has also been confirmed as a product of the UV photolysis of simple (H₂O:CO:NH₃) interstellar ice analogues. Glycolic acid has two conformers: The SSC, or syn-syn-cis, conformer is the most stable species, followed by the trans conformer ATT, anti-trans-trans. Previous rotational spectral study of glycolic acid reported lines in the range of 113 – 318 GHz. We have extended the spectra of both the SSC and ATT conformers from 318 GHz to 1 THz using long-pathlength direct absorption flow cell spectroscopy. Here we will report on the spectroscopic results and the associated analysis for glycolic acid.

Interstellar detections of isocyanic acidSnyder, L. E. & Buhl, D. 1972, ApJ, 177, 619. methyl isocyanateHalfen, D. T., Ilyushin, V. V., & Ziurys, L. M. 2015, ApJ, 812, L5. Cernicharo, J., Kisiel, Z., Tercero, B., et al. 2016, A&A, 587, L4. and very recently also ethyl isocyanateRodríguez-Almeida, L. F., Rivilla, V. M., Jiménez-Serra, I., et al. 2021, A&A, 654, L1.pen the question of the possible detection of the related molecule vinyl isocyanate in the interstellar medium. Similarly, astronomical observations of keteneTurner, B. E. 1977, ApJ, 213, L75.laces vinyl ketene among the species of potential interstellar relevance. In the present work, both vinyl species were generated by thermolysis of suitable precursors at 500^°C and their room-temperature rotational spectra were recorded between 218 and 330 GHz using the Prague millimeter wave spectrometerKania, P., Stríteská, L., Simecková, M., & S. Urban. 2006, J. Mol. Struct., 795, 209. The spectroscopic measurements and analyses presented here will allow to search for both molecules in the millimeter wave surveys of interstellar sources such as those recorded by Atacama Large Millimeter/submillimeter Array.
Acknowledgments: L.K., J.K., K.V., K.L., and P.K. acknowledge the financial fundings from the Czech Science Foundation (GACR, grant No. 19-25116Y) and the Ministry of Education, Youth and Sports of the Czech Republic (MSMT, grant No. 8J21FR006). J.C.G. thanks the Barrande project No. 46662VH and the Centre National d'Etudes Spatiales (CNES) for a grant BC U32-4500065585.

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Snyder, L. E. & Buhl, D. 1972, ApJ, 177, 619., Halfen, D. T., Ilyushin, V. V., & Ziurys, L. M. 2015, ApJ, 812, L5. Cernicharo, J., Kisiel, Z., Tercero, B., et al. 2016, A&A, 587, L4., Rodríguez-Almeida, L. F., Rivilla, V. M., Jiménez-Serra, I., et al. 2021, A&A, 654, L1.o Turner, B. E. 1977, ApJ, 213, L75.p Kania, P., Stríteská, L., Simecková, M., & S. Urban. 2006, J. Mol. Struct., 795, 209..

Large organic molecules of extraordinary complexity have recently been found in diverse regions of the interstellar medium (ISM). In this context, we aim to provide accurate frequencies of the ground vibrational state of two key aliphatic aldehydes, n-butyraldehyde, and its branched-chain isomer i-butyraldehyde. We employed a frequency modulated millimeter-wave absorption spectrometer to measure the rotational features of n- and i-butyraldehyde; several thousands of transitions belonging to the lower-energy conformers have been assigned up to 325 GHz. A precise set of the relevant rotational spectroscopic constants have been determined for each structure as a first step to identifying both molecules in the ISM. We then used the spectral line survey named Re-Exploring Molecular Complexity with ALMA (REMoCA), performed toward the star-forming region Sgr B2(N) with ALMA to search for n- and i-butyraldehyde. We also searched for both aldehydes toward the molecular cloud G+0.693-0.027 with IRAM 30m and Yebes 40m observations. We report the nondetection of these isomers toward both astronomical sources. Our astronomical results indicate a leap around one order of magnitude in the aldehyde’s abundance while increasing the level of complexity.