Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I. It is also a valued industrial reagent and building block in synthesis of pharmaceuticals and other organic compounds. In low concentrations, its odor resembles freshly cut hay or grass. Some soldiers during the First World War stated that it smelled faintly of mayblossom. In addition to its industrial production, small amounts occur naturally from the breakdown and the combustion of organochlorine compounds, such as those used in refrigeration systems. The name, sounding similar to "phosphine", does not mean it has any phosphorus.
Chloroform/oxygen mixtures are unreactive in the dark up to 290
C, suggesting catalyst-assisted air oxidation in our samples[ Kirk-Othmer Concise Encyclopedia of Chemical Technology]. Possible catalysts include surface iron(III) colorant of inadequately washed brown glass and the alkene preservative if peroxidized. While addition of trace iron(III) and air to chloroform of an older lot doubled the phosgene content overnight to 0.012%, this was more than 10-fold less than the rate observed after simple air exposure of the problematic chloroform, thereby indicating another catalyst.
Prudence suggests that alkene-preserved chloroform bottles be tested for phosgene. Filter paper strips, wetted with 5% diphenylamine, 5% dimethylaminobenzaldehyde, and then dried, turn yellow in phosgene vapor. The use of ethanol-preserved chloroform is desirable because ethanol, unlike alkenes, reacts quickly with phosgene. Furthermore, more ethanol than amylene is added commercially, providing extra protection against oxidation
Chloroform/oxygen mixtures are unreactive in the dark up to 290
C, suggesting catalyst-assisted air oxidation in our samples[ Kirk-Othmer Concise Encyclopedia of Chemical Technology]. Possible catalysts include surface iron(III) colorant of inadequately washed brown glass and the alkene preservative if peroxidized. While addition of trace iron(III) and air to chloroform of an older lot doubled the phosgene content overnight to 0.012%, this was more than 10-fold less than the rate observed after simple air exposure of the problematic chloroform, thereby indicating another catalyst.Prudence suggests that alkene-preserved chloroform bottles be tested for phosgene. Filter paper strips, wetted with 5% diphenylamine, 5% dimethylaminobenzaldehyde, and then dried, turn yellow in phosgene vapor. The use of ethanol-preserved chloroform is desirable because ethanol, unlike alkenes, reacts quickly with phosgene. Furthermore, more ethanol than amylene is added commercially, providing extra protection against oxidation
