Diphosgene converts to phosgene upon heating or upon catalysis with charcoal. It is thus useful for reactions traditionally relying on phosgene. For example, it convert amines into isocyanates, secondary amines into carbamoyl chlorides, carboxylic acids into acid chlorides, and formamides into isocyanides. Diphosgene serves as a source of two equivalents of phosgene:
With α-amino acids diphosgene gives the acid chloride-isocyanates, OCNCHRCOCl, or N-carboxy-amino acid anhydrides depending on the conditions.
It hydrolyzes to release HCl in humid air.
Diphosgene has supplanted phosgene in some large scale industrial reactions such as the production of (di-)isocyanates from of amines because it is safer to handle than phosgene.
Poisonous pen letters; Early warning: Pillar-boxes tops changed colour during WWII thanks to a special paint which could 'sense' toxic gas in the air. The black and white stripes aided visibility during the blackouts.
Jun 27, 2007; QUESTION When I was a lad during World War II in London, the tops of allthe pillar-boxes were painted in a different colour. I...