Methanol was one of the earliest molecules to be detected by means of radio astronomy. A plethora of reports deserve mentioning here. Therefore, this documentation may well be incomplete for quite a while.
J. A. Ball, C. A. Gottlieb, A. E. Lilley, and H. E. Radford
gave an account of the
Detection of Methyl Alcohol in Sagittarius
Astrophys. J. 162, L203–L210 (1970).
They used the 140-foot Greenbank radio telescope for the 1₁₀ – 1₁₁ transition near 834 MHz to detect methanol in emission from Sagittarius (Sgr) A and B2.

C. A. Gottlieb, J. A. Ball, E. W. Gottlieb, and D. F. Dickinson
investigated
Interstellar Methyl Alcohol
Astrophys. J. 227, 422–432 (1979).
They used the 11 m Kitt Peak radio telescope to search for the J = 2 – 1 transitions of CH₃OH, ¹³CH₃OH, and CH₃OD in the 3 mm region toward several galactic sources. CH₃OH was detected toward 14 sources, at least the majority of these are hot-core sources. The identification of ¹³CH₃OH lines toward Sgr B2 may well be correct (the ¹²C to ¹³C ratio of somewhat less than 10 is probably affected by opacity of the CH₃OH lines), but the identification of CH₃OD toward the same source is definitively incorrect; see for example:
A. Belloche, H. S. P. Müller, R. T. Garrod, and K. M. Menten
Exploring Molecular Complexity with ALMA (EMoCA): Deuterated Complex Organic Molecules in Sagittarius B2(N2)
Astron. Astrophys. 587, Art. No. A91 (2016).

F. F. Gardner, J. B. Whiteoak, J. Reynolds, W. L. Peters, and T. B. H. Kuiper
announced the
First Detection of the ¹⁸O Isotope of Methanol
Mon. Not. R. Astron. Soc. 240, 35P–40P (1989).
The NASA's 70 m dish at Tidbinbilla was used to detect the J_K = 2₀ − 3₋₁ transition of CH₃¹⁸OH near 11.6 GHz toward Sgr B2. The derived ¹⁶O to ¹⁸O ratio of 210 ± 40 is in line with other results obtained toward the galactic center.

R. Mauersberger, C. Henkel, T. Jacq, C. M. Walmsley
detected
Deuterated Methanol in Orion
Astron. Astrophys. 194, L1−L4 (1988).
About one dozen transitions of CH₃OD were detected with good signal-to-noise ratios toward Orion KL between 110 and 230 GHz using the IRAM 30 m telescope.

T. Jacq, C. M. Walmsley, R. Mauersberger, T. Anderson, E. Herbst, F. C. De Lucia
gave an account of the
Detection of interstellar CH₂DOH
Astron. Astrophys. 271, 276–281 (1993).
The IRAM 30 m telescope was employed to detect six lines of CH₂DOH toward Orion-IRc2 between 90 and 230 GHz. Several CH₃OD transitions were observed newly around 136 GHz. The abundance of CH₂DOH was estimated to be slightly higher (by up to 50 %) than that of CH₃OD.

B. Parise, C. Ceccarelli, A. G. G. M. Tielens, E. Herbst, B. Lefloch, E. Caux, A. Castets, I. Mukhopadhyay, L. Pagani, and L. Loinard
announced the
Detection of Doubly-deuterated Methanol in the Solar-type Protostar IRAS 16293−2422
Astron. Astrophys. 393, L49–L53 (2002).
About a dozen lines of CHD₂OH were detected between 89 and 224 GHz with very modest to good signal-to-noise ratios employing the IRAM 30 m telescope. The CH₂DOH isotopolog has an abundance about five times higher. The comparisons to CH₃OH are incorrect because of severe opacity of these lines.

In addition,
B. Parise, C. Ceccarelli, A. G. G. M. Tielens, A. Castets, E. Caux, B. Lefloch, and S. Maret
were
Testing Grain Surface Chemistry: a Survey of Deuterated Formaldehyde and Methanol in Low-mass Class 0 Protostars
Astron. Astrophys. 453, 949–958 (2006).
CHD₂OH was also found toward the low-mass protostars IRAS 2, IRAS 4A, and IRAS 4B in the NGC 1333 molecular cloud.

B. Parise, A. Castets, E. Herbst, E. Caux, C. Ceccarelli, I. Mukhopadhyay, and A. G. G. M. Tielens
gave an account of the
First Detection of Triply-deuterated Methanol
Astron. Astrophys. 416, 159–163 (2004).
A dozen lines of CD₃OH were detected around 158 GHz toward IRAS 16293−2422 with very modest to reasonable signal-to-noise ratios employing the IRAM 30 m telescope. The column density of CH₃OH was derived from that of ¹³CH₃OH. The CH₃OH : CH₂DOH : CHD₂OH : CD₃OH ratios were about 126 : 38 : 7.7 : 1.

V. V. Ilyushin, H. S. P. Müller, J. K. Jørgensen, S. Bauerecker, C. Maul, R. Porohovoi, E. A. Alekseev, O. Dorovskaya, F. Lewen, S. Schlemmer, and R. M. Lees
carried out an
Investigation of the Rotational Spectrum of CD₃OD and an Astronomical Search toward IRAS 16293–2422
Astron. Astrophys. 677, Art. No. A49 (2023).
The authors found some evidence for the presence of this isotopolog in PILS data toward this low-mass protostar. About seven lines are not blended to only partially blended; the signal-to-noise ratio of some lines is only modest. The derived abundance of 0.02 % with respect to the main isotopolog may be reasonable compared to 0.33 % obtained for CD₃OH described below. Nevertheless, the identification should be viewed as very tentative because of the limited amount of lines and the complexity found in deueration ratios. Identifications of CH₂DOD and also CHD₂OD should be more promising.

H. S. P. Müller, V. V. Ilyushin, A. Belloche, F. Lewen, and S. Schlemmer
reported on an
Investigation of the Rotational Spectrum of CH₃¹⁷OH and its Tentative Detection toward Sagittarius B2(N)
Astron. Astrophys. 688, Art. No. A201 (2023).
The authors report a tentative detection of this isotopolog in the ReExploring Molecular Complexity with ALMA survey at 3 mm. Only one unblended and one partially blended line were identified, many more were severely bleded or too weak. The derived CH₃¹⁸OH to CH₃¹⁷OH ratio of ~3.3 is along ¹⁸O to ¹⁷O ratios found for other molecules in the Galactic Center as is the CH₃¹⁶OH to CH₃¹⁸OH ratio of 240.

F. J. Lovas, R. D. Suenram, L. E. Snyder, J. M. Hollis, and R. M. Lees
reported on the
Detection of the Torsionally Excited State of Methanol in Orion A
Astrophys. J. 253, 149–153 (1982).
Three lines partaining to four transitions of torsionally excited methanol were detected with the 11 m Kitt Peak radio telescope at 3 mm.

V. V. Ilyushin, H. S. P. Müller, J. K. Jørgensen, S. Bauerecker, C. Maul, Y. Bakhmat, E. A. Alekseev, O. Dorovskaya, S. Vlasenko, F. Lewen, S. Schlemmer, K. Berezkin, and R. M. Lees
investigated the
Rotational and Rovibrational Spectroscopy of CD₃OH with an Account of CD₃OH toward IRAS 16293−2422
Astron. Astrophys. 658, Art. No. A127 (2022).
Using the Protostellar Interferometric Line Survey (PILS) carried out with ALMA, several lines of torsionally excited CD₃OH were detected between 329 and 363 GHz; nine unblended or only slightly blended lines of this vibrationally excited state were shown in a figure around 350.6 GHz. The rotational temperature was ~225 K, and the CH₃OH to CD₃OH ratio was about 300. Lines of torsionally excited deuterated methanol will be more prominent for ¹²C isotopologs containing fewer D atoms.

V. V. Ilyushin, H. S. P. Müller, M. N. Drozdovskaya, J. K. Jørgensen, S. Bauerecker, C. Maul, R. Porohovoi, E. A. Alekseev, O. Dorovskaya, O. Zakharenko, F. Lewen, S. Schlemmer, L.-H. Xu, and R. M. Lees reported on the
Rotational Spectroscopy of CH₃OD with a reanalysis of CH₃OD toward IRAS 16293–2422
Astron. Astrophys. 687, Art. No. A220 (2024).
Unsurprisingly, the authors detected in their PILS data also many lines of CH₃OD in v_t = 1. These lines were instrumental in determing the rotational temperature of ~190 K, which is in accord with ~225 K mentioned in the previous paragraph, but considerably lower than the estimated ~300 K earlier. Adopting earlier values, the amount of CH₃OD is ~0.32 % that of CH₃OH, and the CH₂DOH to CH₃OD ratio is ~22.5, which translates into a deuteration ratio per H atom of ~7.5.

H. S. P. Müller, V. V. Ilyushin, A. Belloche, F. Lewen, and S. Schlemmer
reported on an
Investigation of the Rotational Spectrum of CH₃¹⁷OH and its Tentative Detection toward Sagittarius B2(N)
Astron. Astrophys. 688, Art. No. A201 (2023).
The authors report a tentative detection of torsionally excited CH₃¹⁸OH in the ReExploring Molecular Complexity with ALMA survey at 3 mm besides several a clear identification of this isotopolog in its ground torsional state.

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Contributor(s): H. S. P. Müller; 04, 2022; 08, 2024

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