Abstract: Illustrated by the purification of diphenyl carbonate (DPC), diaryl carbonates are purified and freed of contaminants such as inorganic and organic chlorides, metal ions, iron components and color bodies. The process is a two-stage procedure starting with a water wash of the molten carbonate followed by distillation. Crude DPC is charged to the wash tank and is washed in the molten state three times. Fresh steam condensate is used for each wash which consists of a period of agitation followed by decantation then water removal. After the third wash, the molten DPC is transferred to a still for distillation. The rag layer which is formed at the water/DPC interface during washing is purged and not allowed to pass through to the still. A flash distillation is carried out under constant vacuum. Three overhead cuts are taken--lights, intermediate and product DPC depending on the temperature of the overhead vapor.

Abstract: A novel process is described for the preparation of dihydrooxadiazinones by cyclizing a hydrazone under basic conditions. The hydrazones are prepared by reaction of a carbazate with an acyl alcohol that is derived from the hydrolysis of an alpha bromo precursor.