ISOCYANIC ACID, Hydrogen isocyanate CHNO CAS NO.75-13-8

The primary use of methyl isocyanate (MIC, CAS no. 624-83-9) is as a chemical intermediate in the production of carbamate pesticides. MIC is also used to produce polyurethane foam and plastics (ATSDR, 2002). Isocyanic acid (ICA, Cas no. 75-13- 8) does not have commercial uses because of its instability. The potential for occupational exposure to ICA largely arises when it is generated as a thermal degradation product of other industrial processes. Ethyl isocyanate is a liquid used commercially to make pharmaceuticals and pesticides (NJDHSS, 2000). Phenyl isocyanate (PIC, CAS no. 103-71-9) is a trace constituent in commercial diphenyl methane diisocyanate products.

Isocyanic acid (ICA, Cas no. 75-13- 8) is a strong organic acid with a kPa of 3.5. ICA is a very reactive compound that can readily transform into other substances. It can lose a proton in an aqueous environment under certain conditions, particularly if a strong base is present, forming an isocyanate. ICA is a tautomer of the less stable, cyanic acid (CAS no. 420-05-3). These forms interchange by a tautomerisation reaction, involving the migration of a hydrogen atom or proton accompanied by a switch of a double bond. ICA is an unstable liquid above 0o C with a tendency to polymerise. The primary polymerisation product, which is also generated in the gas form, is cyanuric acid (CAS no. 108-80-5), a cyclic trimer. ICA is soluble in water, but disintegrates both via ionisation and by formation of ammonia and carbon dioxide.