Mechanism of the Ullmann condensation

It has been found that the condensation rate of 1-amino-4-bromoanthraquinone-2-sulphonic acid ( I ) with 1,3-diaminobenzene-4-sulphonic acid ( II ) giving 1-amino-4-(3'-amino-4'-sulphoanilino)anthraquinone-2-sulphonic acid ( III ) in media of NaHCO 3 -CO 2 and NaHCO 3 -Na 2 CO 3 with catalysis by CuI obeys the kinetic relation *u = k [I][II][Cu + ][CO 2- 3 ], being controlled by the kinetic relation *u = k [I][II][Cu + ] 2 [PO 3- 4 ] in media of NaH 2 PO 4 -Na 2 HPO 4 buffers. The suggested reaction mechanism presumes formation of a bifunctional catalyst CuCO - 3 or Cu 2 PO - 4 which splits off the proton and bromide anion from the reaction intermediate in the rate-limiting step.