The propene molecule C3H6, aka propylene,
has been identified in spectra recorded toward TMC-1 by
N. Marcelino, J. Cernicharo, M. Agúndez, E. Roueff, M. Gerin, J. Martín-Pintado, R. Mauersberger, and C. Thum,
Discovery of Interstellar Propylene (CH2CHCH3): Missing Links in Interstellar Gas-Phase Chemistry
Astrophys. J. 665, L127L130 (2007).
Six rotational transitions each split into two A and E components due to the CH3 interal rotation were observed plus one A component for which the E line is overlapped. The observation of this molecule in TMC-1 was rather surprising because apparently noone in the community considered such an almost saturated molecule to be likely in this source especially because of thus far missing routes to this molecule. Even more remarkable is the detection because of the high abundance; a column density of 4 × 1013 cm-2 was derived; comparable to the abundance of c-C3H2.
M. Agúndez, J. Cernicharo, and M. Guélin
reported the detection of propene by the two methyl internal rotor states of the 505 404 transition near 86.65 GHz with the IRAM 30 m telescope toward 4 out of 5 dark clouds (Lupus-1a, L1495B, L1521F, and Serpens South 1a) in their report on
Discovery of Interstellar Ketenyl (HCCO), a Surprisingly Abundant Radical
Astron. Astrophys. 577, Art. No. L5 (2015).
Emission of up to three more rotational transitions were also detected.