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]
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
[change | change source]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]
References
[change | change source]- ↑ International Union of Pure and Applied Chemistry. "Isocyanates". Compendium of Chemical Terminology Internet edition.
- ↑ 2.0 2.1 Guo, Zhuhua; Ding, Xiaoshu; Wang, Yanji (2024). "How to Get Isocyanate?". ACS Omega. 9 (10): 11168–11180. doi:10.1021/acsomega.3c10069. PMC 10938423. PMID 38496933.
- ↑ A. John Speziale and Lowell R. Smith (1966), "α-Chloroacetyl isocyanate", Org. Synth., 46: 16, doi:10.15227/orgsyn.046.0016