The mechanic study of the Pd-catalyzed synthesis of diphenylcarbonate with heteropolyacid as a cocatalyst

The reaction to synthesize diphenyl carbonate (DPC) by an oxidative carbonylation of phenol with CO and O2 has been found to proceed through the second-order of phenol concentration. The activation energy Ea, ΔS and ΔH are 27.0 kcal mol−1, −6.43 cal mol−1 and 26.3 kcal mol−1, respectively. The kinetic and additive data obtained agree with the proposed mechanism as follows: Pd(OAc)2 reacts with an ammonium phenoxy salt to give AcOPdOPh which then reacts with CO to form AcOPdCOOPh. This species leads to PhOPdCOOPh which undergoes reductive elimination to give DPC and Pd(0). This Pd(0) is reoxidized to Pd(II) by the help of a heteropolyacid very effectively.