A safe and green benzylic radical bromination experiment

Abstract

Radical chemistry is an essential part of the organic chemistry curriculum. Free radical halogenation experiments provide an excellent opportunity to introduce important topics related to the outcome and mechanism of organic reactions. In this communication, a green photochemically activated benzylic bromination of p-toluic acid is described. In contrast with previous versions of this reaction, visible light provides the energy necessary to homolytically cleave the Br—Br bond and initiate the radical cascade. Thus, photochemical activation allows a safer, faster, and cheaper alternative to chemical free radical initiators. Furthermore, the reaction is conveniently performed in environmentally friendly acetonitrile, as a replacement for toxic and ozone-depleting chlorinated solvents, such as the usual carbon tetrachloride.