HNCO

Isocyanic acid, abbreviated as HNCO, is the simplest member of the isocyanic acids and is a small, polar molecule. Its conventional skeletal structure is H–N=C=O, and the molecule exists in tautomeric equilibrium with cyanic acid (HOCN), with HNCO being the predominant form in most conditions.

HNCO has attracted attention for its presence in both terrestrial and extraterrestrial contexts. It has been detected in combustion and biomass-burning environments on Earth and also in the interstellar medium, where its rotational transitions are observed by radio telescopes. In space, HNCO is considered a useful tracer of nitrogen- and oxygen-bearing chemistry and is part of networks that describe molecular complexity in star-forming regions.

In terms of formation and reactions, HNCO can be produced industrially or in laboratory settings by processes such as the thermal decomposition of urea. It can also form through the oxidation of nitrogen-containing organics during high-temperature processes. In biological and chemical contexts, HNCO is reactive with amino groups and can carbamylate proteins and other biomolecules, contributing to toxicity and serving as a chemical hazard in some exposure scenarios.

Astrochemically, HNCO is of interest because it relates to cyanate chemistry and the growth of complex organic molecules in space. Proposed formation routes include both grain-surface chemistry and gas-phase reactions, with desorption from grains releasing HNCO into the gas phase under suitable conditions. Related species include the cyanate ion (OCN−) and the tautomeric form HOCN.

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