Cyanopentadiyne, CH3C5N, also known as
methylcyanodiacetylene, has been detected first by:
L. E. Snyder, T. L. Wilson, C. Henkel, P. R. Jewell, and C. M. Walmsley,
Detection of Interstellar Methylcyanodiacetylene in the Dark Dust Cloud TMC 1
Bull. Am. Atron. Soc. 16, 959 (1984).
Only three lines were detected, of which one apparently was blended. Therefore, this detection was deemed tentative.
More recently, the 100 m GBT was used to detect the J =
12 11 to 16 15 transitions with
K = 0 and 1 between 18.6 and 24.9 GHz in emission,
also toward TMC-1, by
L. E. Snyder, J. M. Hollis, P. R. Jewell, F. J. Lovas, and A. Remijan,
Confirmation of Interstellar Methylcyanodiacetylene;
Astrophys. J. 647, 412417 (2006).