Synthesis and Formation of Phosgene

It is rarely necessary, nowadays, to prepare phosgene in the laboratory since cylinders and lecture bottles are generally readily available (see Section 3.1.5.3). The purpose of this Chapter is threefold  

we have concentrated in this Chapter not only upon those reactions which constitute an efficient synthesis of phosgene or labelled phosgene, but also (owing to the exceptional toxicity of the compound) on those reactions which generate even comparatively low yields and which could be conceivably problematical in the chemical plant environment, and in both the organic and inorganic laboratory. 

Sources of industrial emission of phosgene have been described in Sections 3.3 and 3.6, and its environmental formation has been dealt with in Section 3.7. Useful reviews concerning the synthesis or formation of phosgene have appeared [578,781,996,1019,1378,1379,1464], and the manufacture and purification of phosgene is the subject of Chapter 4. 

The manufacture of any large-scale, industrially important compound is susceptible to changes in the availability of raw materials, the economic climate, legislative constraints, and the particular manufacturer s local considerations. There is little doubt, at the present time, that (under the vast majority of conditions) the synthesis of phosgene from carbon monoxide and dichlorine, catalysed by activated charcoal, constitutes the most favourable method in economic terms. 

However, those chemical manufacturers (particularly the smaller contract manufacturer) who may not be sited near to a CO (or Cl j) producing facility may need to have alternative means of generating phosgene at their disposai, for their various processes (see Section 3.1.6). Indeed, in view of the anticipated legislation in Europe, the U.S.A., and elsewhere to control, or prohibit, the transportation of phosgene, those processes which depend upon phosgene (where it is not locally available) could be severely prejudiced in the absence of such alternatives. 

---