The preparation of 4,4'-Oxydiphthalic anhydride(1823-59-2) is as follows:Chlorophthalic anhydride (30g, 160mmol), tetraphenyl phosphonium bromide (0.3g, 0.7mmol), and 2,5-dichlorobenzoic acid (0.08g, 0.4mmol) were heated to approximately 220℃. Potassium carbonate (7.95g, 58mmol) was added over 45 minutes. The reaction was sampled after addition of the potassium carbonate and showed a 24.9% conversion to 4,4'-oxydiphthalic anhydride. The reaction was heated for an additional 45 minutes. The reaction mixture was diluted with 1,2,4-trichlorobenzene (90g) and filtered. The 4,4'-oxydiphthalic anhydride was allowed to crystallize and was collected, washed with 1,2,4-trichlorobenzene followed by hexane, and dried in an air circulating oven at 120℃. to give crude 4,4'-oxydiphthalic anhydride, 12.9g.
