April 2004

Isocyanic Acid

The detection of isocyanic acid (HNCO) in the interstellar medium was first reported in 1972 by Snyder & Buhl. It has since been observed in extragalactic sources. In comets, it was first observed in Hyakutake and then in Hale-Bopp.

HNCO has a dipole moment comparable to that of water. It is a strong organic acid with a pKa value of about 3.5. As such, it can lose a proton in an aqueous environment under certain conditions, particularly if a strong base is present. In this case, OCN is formed.

HNCO is the smallest molecule containing the four primary biogenic elements. There are three other, less stable isomers of HNCO. The detection of the next most stable form, cyanic acid (HOCN), was reported in 2009 by Brünken et al. and subsequently confirmed in 2010.

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