Diphosgene toxicity

Trichloromethyl chloroformate (diphosgene) is used as a safe substitute for highly toxic phosgene gas. The latter is generated in situ by addition of catalytic amounts of tertiary amines or amides, or active carbon. Diphosgene also disproportionates to 2 equivalents of phosgene on heating above 250°C. 

The traditional use of phosgene in Scheme 4 can be avoided by substituting it with the less toxic triphosgene, which gives comparable yields of the M-car-boxyanhydrides. Diphosgene may also be used to form the NCA, but the reaction requires the use of charcoal and is not as reliable. Free amino acids have also been converted to their corresponding NCAs by the use of benzyl chloroforma-te with thionyl chloride. 

Green Cross Gases. This includes substances with a high vapour tension and great toxic power on the respiratory tract phosgene, trichloromethyl chloroformate (diphosgene), chloro-picrin, etc. 

It is, therefore, about five times more toxic than chlorine, but only aiwut half as toxic as phosgene and diphosgene, so that, while it was great improvement over < hlorine when first us d, it was soon displaced by diphosgene and chlorpicrin when these more powerful compounds were introduced. 

The toxicity of diphosgene Is about the same as that of phosgene. In fact, it is probable that the toxicity of diphosgene is not a specific proi>erty of that compound, but is derived from the phosgene molecules into which it decomposes in the tissues of the body. 

As noted by S. Damie (Ref.34), the toxicity of both diphosgene and triphosgene is exactly the same of phosgene since both decompose on heating and upon reaction with any nucleophile. Even a trace of moisture leads to formation of phosgene. 

Diphosgene is listed as highly toxic in the United States and as very toxic in the European Union. The primary routes of entry for diphosgene are through... 

Inhalation is the major route of exposure. Diphosgene is extremely damaging to mucous membranes, eyes, skin, and the respiratory tract, and may cause minor irritation to severe tissue damage and death. Toxicity effects vary with the concentration of vapor and the length of exposure. Signs and symptoms of toxicity may be immediate or delayed. The delayed (up to 6h) acute respiratory distress syndrome is characteristic of chocking agent inhalation. 

K-Stoff was introduced by the Germans in June 1915 as a more lethal replacement for chlorine. A low-boiling liquid (boiling point 1°C), it was loaded into artillery shells, hence was more convenient to use in combat, and could be delivered independent of the prevailing wind direction. It was manufactured as a mixture of chloromethyl chloroformate and dichloromethyl chloroformate, variously reported to be 70/30 and 90/10, respectively. It is about twice as toxic as chlorine. K-Stoff was itself soon replaced by the more lethal phosgene and diphosgene. The latter are of comparable toxicities, about six times more toxic than chlorine, and soon became the most heavily used nonpersistent lethal agents of the war ... 

Diphosgene (Trichloromethyl chloroformate), CICOOCCI0, Mol. wt. 197.85, b.p. 128°, 49°/50 mm. toxic, asphyxiating gas used in the first world war as a poison gas. This reagent is generally prepared by chlorination hv) of methyl formate or methyl chloroformate. 

Diisocyanates are usually synthesized by phosgenation of the corresponding diamines. A tabulation of diisocyanates synthesized up to 1972 with pertinent methods of synthesis is available (11). Instead of the toxic phosgene gas, the liquid trichloromethyl chloroformate (diphosgene) (12) or the solid bistrichloromethyl carbonate (triphosgene) (13) can be used in the laboratory (see PHOSGENE). Also, oligomeric t-butylcarbonates are used to convert diamines into diisocyanates (14). 

Like phosgene, total numbers of casualties firom diphosgene in World War I were relatively few compared to mustard, but it was one of the most deadly CW agents used in shells during the war. There is also another analogue, triphosgene, that possesses the toxic and physical properties of diphosgene, but information on its actual use is scarce. 

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