High‐yield production of p‐diethynylbenzene through consecutive bromination/dehydrobromination in a microreactor system

Abstract Polyarylacetylene resins have received great attention due to their outstanding heat resistance, while the absence of an efficient method to produce their monomer, p ‐diethynylbenzene ( p ‐DEB), has discouraged their commercial development. Industrial production of p ‐DEB consists of bromination and dehydrobromination in a semi‐batch reactor, state of the art yield from which is only 70%–75%. Herein, a combined effort of byproduct characterization and density functional theory calculations revealed that side reactions mainly consisted of aromatic substitution which would be promoted by thermal runaway derived from exothermic bromination due to higher activation energy of side reactions. From these considerations, we developed a microreactor system to enhance heat transfer thereby mitigating byproduct formation, from which a p ‐DEB yield of 99.2% could be achieved. Moreover, the high heat removal efficiency avoided the use of slow feeding and reactant dilution required in semi‐batch operation, thereby shortening the reaction time to 14 s while generating more concentrated product.