Cyanopropyne, CH3C3N, also known as
methylcyanoacetylene or methylpropionitrile, has been detected
with the 45 m NRAO telescope in the J =
6 5 to 8 7 transitions with
K = 0 and 1 between 27.7 and 33.1 GHz
in emission toward TMC-1, by
N. W. Broten, J. M. MacLeod, L. W. Avery, W. M. Irvine, B. Höglund, P. Friberg, and Å. Hjalmarson,
Detection of Interstellar Methylcyanoacetylene
Astrophys. J. 276, L25L29 (1984).
In addition, the J = 5 4, K = 0 transition was barely detected.