end products and recycled into the process, with any remaining phosgene decomposed in water using activated carbon as the catalyst. Industrial uses Phosgene is used in industry for the production of aromatic di-isocyanates like toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI), which are precursors for production of polyurethanes. It is also used to form polycarbonates, via a reaction with bisphenol A. More than 90% of the worldwide produced phosgene is used in these processes, with the biggest production units located in the United States (Texas and Louisiana), Germany, Shanghai, Japan, and South Korea. The most important producers are Dow Chemical, Covestro, and BASF. Phosgene is used in the production of aliphatic diisocyanates such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), which are precursors for the production of advanced coatings. Phosgene is also used to produce monoisocyanates, used as pesticide precursors (e.g. methyl isocyanate (MIC). Laboratory uses In the research laboratory, due to safety concerns phosgene nowadays finds limited use in organic synthesis. A variety of substitutes have been developed, notably trichloromethyl chloroformate ("diphosgene"), a liquid at room temperature, and bis(trichloromethyl) carbonate ("triphosgene"), a crystalline substance. Aside from the widely used reactions described above, phosgene is also used to produce acyl chlorides from carboxylic acids: RCO2H + COCl2 → RC(O)Cl + HCl + CO2 For this application, thionyl chloride is commonly used instead of phosgene in academic settings. Phosgene is used to produce chloroformates such as benzyl chloroformate: ROH + COCl2 → ROC(O)Cl + HCl In these syntheses, phosgene is used in excess to prevent formation of the corresponding carbonate ester. With amino acids, phosgene (or its trimer) reacts to give amino acid N-carboxyanhydrides. More generally, phosgene acts to link two nucleophiles by a carbonyl group. For this purpose, alternatives to phosgene such as carbonyldiimidazole (CDI) are safer. CDI itself is prepared by reacting phosgene with imidazole. Phosgene is stored in metal cylinders. In the US, the cylinder valve outlet is a tapered thread known as "CGA 160" that is used only for phosgene. Other reactions Phosgene reacts with water to release hydrogen chloride and carbon dioxide: COCl2 + H2O → CO2 + 2 HCl Analogously, upon contact with ammonia, it converts to urea: COCl2 + 4 NH3 → CO(NH2)2 + 2 NH4Cl Halide exchange with nitrogen trifluoride and aluminium tribromide gives COF2 and COBr2, respectively. Chemical warfare It is listed on Schedule 3 of the Chemical Weapons Convention: