Catalytic hydrochlorination of acetylene on PdCl2/C supported catalysts: Kinetic isotopic effect of HCl/DCl, stereoselectivity, and mechanism

Abstract

Two routes of catalytic hydrochlorination of acetylene were found by the isotopic label method for systems with supported palladium K₂PdCl₄/C and Н₂PdCl₄/C catalysts: with formation of the products of syn- and anti-addition of the H(D)Cl molecule to the triple bond of acetylene. Two isotopic effects that differ in magnitude were determined for these systems from the reaction kinetics and the ratio of the yields of the nondeuterated and monodeuterated isotopomers of the product, which are due to the participation of the H(D)Cl molecule in the two reaction stages: limiting chloropalladation and rapid protodemetallation. The effective activation energies and kinetic isotope effects coincided within the experimental errors, which suggests that the reaction mechanisms are similar and the active centers of the catalysts in systems with K₂PdCl₄/C and Н₂PdCl₄/C are of the same nature.