Isocyanate

In organic chemistry, isocyanate is a functional group (a piece of a molecule) with the chemical formula −N=C=O: a nitrogen atom connected to the larger molecule, with a double bond to a carbon atom, which has its own double bond to an oxygen atom.^[1]

Methyl isocyanate (MIC) is the simplest organic isocyanate. This structural formula shows the chemical bonds between atoms.

Isocyanates are used to make polyurethanes, a type of plastic, and some pesticides. Notable isocyanates include methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and methyl isocyanate (MIC).^[2]

Production

In the chemical industry, isocyanates are made from phosgene and a primary amine (a chemical with a −NH₂ group), with hydrogen chloride as a byproduct. A simple example is the reaction of phosgene with methylamine to make methyl isocyanate:

COCl₂ + CH₃NH₂ → CH₃NCO + 2 HCl

This reaction is conducted in anhydrous conditions, meaning no water is present, because water can cause a runaway reaction with isocyanates. The water-isocyanate reaction is what caused the Bhopal disaster, the worst industrial accident in history.

Phosgene is a dangerous gas that needs special equipment to use safely. Oxalyl chloride is an alternative to phosgene used in research.^[3] Researchers are interested in other ways to make isocyanates without using chlorine compounds.^[2]