The detection of cyanodiacetylene (HC₅N) through observations of multiple rotational transitions was spread through a number of reports across the span of several years in a variety of interstellar objects. The initial 1976 report, by Avery et al., found the 4-3 line in Sgr B2 using the 46 m telescope at Algonquin Radio Observatory in Canada. Two more lines, 1-0 and 8-7, were reported later the same year by Broten et al., also in Sgr B2 but using the facility in Parkes, Australia. In 1977, Little et al. reported observing the 9-8 line in the Heiles2 dust cloud. The same line was subsequently observed by Winnewisser & Walmsley in IRC +10216 in 1978. A fifth line, for the 2-1 transition, was found in Sgr B2 and TMC-1 by Gardner & Winnewisser and published in late 1978. The 3-2 transition was observed by Rodriguez & Chaisson in 1980, while Jennings & Fox four consecutive transitions (7-6, 8-7, 9-8, 10-9) in 1982.

Cyanodiacetylene (or cyanobutadiyne or 2,4-pentadiynenitrile) has two CC triple bonds, making it the first member of the cyanopolyyne family. While species as large as HC₁₁N have been observed in space and HC₁₇N in the lab, they are very unstable and don't persist outside low pressure conditions.