On the Detection of Methyl Cyanide, CH3CN, in Space

Methyl cyanide, CH3CN, also known as acetonitrile or cyanomethane, was among the molecules detected early by radioastronomical means. The J = 6 – 5 transitions with Ka = 0 to 5 were observed with the 36 foot NRAO antenna at 2.7 mm toward Sagittarius B; some lines were probably also detected toward Sgr A where the lines were much broader.
P. M. Solomon, K. B. Jefferts, A. A. Penzias, and R. W. Wilson,
Detection of Millimeter Emission Lines from Interstellar Methyl Cyanide
Astrophys. J. 168, L107–L110 (1971).

The molecule was also detected toward dark clouds:
H. E. Matthews and T. J. Sears,
Detection of the J = 1 – 0 transition of CH3CN
Astrophys. J. 267, L53–L57 (1983).

More recently, it was detected toward a low mass proto-star:
S. Cazaux, A. G. G. M. Tielens, C. Ceccarelli, A. Castets, V. Wakelam, E. Caux, B. Parise, D. Teyssier,
The Hot Core around the Low-mass Protostar IRAS 16293-2422: Scoundrels Rule!
Astrophys. J. 593, L51–L55 (2003).

CH313CN was probably detected because its lines are very close to those of the main isotopolog:
S. E. Cummins, S. Green, P. Thaddeus, and R. A. Linke,
The Kinetic Temperature and Density of the Sagittarius B2 Molecular Cloud from Observations of Methyl Cyanide
Astrophys. J. 266, 331–338 (1983);
both 13C species were detected by
E. C. Sutton, G. A. Blake, C. R. Masson, and T. G. Phillips,
Molecular Line Survey of Orion A from 215 to 247 GHz
Astrophys. J. Suppl. Ser. 58, 341–378 (1985).

CH2DCN was detected in several transitions at 2 and 1.3 mm with the IRAM 30 m telecope toward the IRc2 hot core of the Orion Molecular Cloud. The H/D ratio is roughly 0.01, suggesting considerable molecular deuterium enrichment even in hot cores.
M. Gerin, F. Combes, G. Wlodarczak, T. Jacq, M. Guélin, P. Encrenaz, and C. Laurent,
Interstellar Detection of Deuterated Methyl Cyanide
Astron. Astrophys. 259, L35–L38 (1992).

CH3C15N was detected first toward Sgr B2(N) in the course of a line survey around 1.3 mm with SEST by
A. Nummelin, P. Bergman, Å. Hjalmarson, P. Friberg, W. M. Irvine, T. J. Millar, M. Ohishi, and S. Saito,
A Three-Position Spectral Line Survey of Sagittarius B2 between 218 and 263 GHz. I. The Observational Data
Astrophys. J. Suppl. Ser. 117, 427–529 (1998).

CH3CN in its lowest v8 = 1 excited vibrational state was detected with the FCRAO near 111 GHz by
P. F. Goldsmith, R. Krotkov, R. L. Snell, R. D. Brown, and P. Godfrey,
Vibrationally excited CH3CN and HC3N in Orion
Astrophys. J. 274, 184–194 (1983).

Contributor(s): H. S. P. Müller 01, 2010