Diphenyl carbonate → Oxalic acid, diphenyl ester

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Reaction Steps

400 parts of an aqueous solution of sodium hydrogencarbonate having a pH of 10 were added to 200 parts of diphenyl carbonate, obtained through the decarbonylation reaction of diphenyl oxalate using a hydrochloride of tetraphenyl phosphonium chloride as a catalyst, and the mixture was heated to 90° C. and stirred for 1 hour. To the obtained heavy solution (diphenyl carbonate layer) was further added 400 parts of distilled water, and the resulting mixture was heated to 90° C. and stirred for 1 hour. This additional washing step was repeated twice. The resulting heavy solution was purified by distillation in the same manner as in Example 3 at an yield of 90% to obtain diphenyl carbonate containing 1.9 ppm of hydrolyzable chlorine. An ester interchange reaction between this diphenyl carbonate and bisphenol A was carried out in the same manner as in Example 1 except that a disodium salt of bisphenol A was used in place of sodium hydroxide as an ester interchange catalyst in an amount of 1.2×10−5 mole, in terms of sodium, based on bisphenol A, to synthesize polycarbonate. A pellet of this polycarbonate was used for the measurement of its physical properties. The conditions and results are shown in Tables I-A and I-B below.

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