Sources of Phosgene

Emissions of phosgene most commonly arise as a result of its release during manufacture and use, its formation from the decomposition of chlorinated hydrocarbons, and its formation from the photochemical oxidation of air-borne chlorinated organic materials, particularly the C, and C chloroalkanes, and chloroethenes. The location and estimation of air emissions from sources of phosgene have been described by the US Environmental Protection Agency [2088b], Catastrophic emissions and accidental spills and leaks are discussed in Section 3.6. 

Chloride [117371-69-4]. Phosgene-in-a-can C11H10CI2N2O M 257.118 Prod, of reaction of excess pyridine with phosgene. Useful source of phosgene. Light yellow solid. Mp 84-87° dec. Thermally stable, liberates phosgene in soln. King, J.A. et al, J. Org. Chem., 1988, 53, 6145 (synth, ir, pmr, cmr)... 

An excess of phosgene is used during the initial reaction of amine and phosgene to retard the formation of substituted ureas. Ureas are undesirable because they serve as a source for secondary product formation which adversely affects isocyanate stabiUty and performance. By-products, such as biurets (23) and triurets (24), are formed via the reaction of the labile hydrogens of the urea with excess isocyanate. Isocyanurates (25, R = phenyl, toluyl) may subsequendy be formed from the urea oligomers via ring closure. 

Diphenyl carbonate, an alternative source of the carbonate group to phosgene, may be obtained by reacting phenol with phosgene in acqueous caustic soda solution, the reaction being accelerated by tertiary amines. The diphenyl carbonate can be purified by redistillation. 

Potential sources of carbon monoxide hazards include metal-refining processes, in which it is formed as a byproduct and used as a fuel (LEL 12.5%), and running vehicle engines (particularly petrol-driven) or gas-fired heaters in poorly ventilated confined spaces. It is also a feedstock in the manufacture of a variety of chemicals, e.g. methanol, acetic acid, phosgene and oxo-alcohols. 

The oxazolidinediones 94 are crystalline, stable solids that are a convenient source of dipeptides when heated in THF with amino adds. The compounds are prepared fiom N-protected amino adds and phosgene or triphosgene <99JOC2S32>. The diiral oxazolidinediones 95 act as Friedel-Crafts reagents with aromatic hydrocarbons and aluminium chloride, giving the ketones 96 in moderate yield but with high ee <99S423>. ... 

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