Hydrogen isocyanide (HNC) was detected in 1972 via its J=1-0 rotational line at 90.7 GHz by
Snyder & Buhl and
Zuckerman et al. in W51 and
NGC 2264, respectively. While Snyder & Buhl assigned the
line to HNC, definitive experimental data to confirm the assigment was not available until the laboratory study of
Blackman et al. was published in 1976.
Subsequently, the three singly isotopically-subtituted forms were quickly found:
HN13C by Brown et al. in 1976,
DCN by Godfrey et al. in 1977, and
H15NC by Brown et al. also in 1977.
HNC was first detected in an extragalactic source, IC342, by
Henkel et al.
HNC has also been observed in a number of comets, beginning with the detection in
Irvine et al.
HNC is much less stable than
its isomer, hydrogen cyanide (HCN). HNC is often
far more abundant than it would be if interstellar clouds were in chemical equilibrium. But low temperatures and
pressures mean than dark clouds take a very
long time to reach equilibrium.