Solvent-free synthesis of molecular bromine and its application for in situ bromination of aromatic compounds

Synthesis of molecular bromine in solvent-free reaction was studied using two different reaction mixtures. The first mixture consisted of solid KNO3 and gaseous HBr, while the second setup used solid NaBr, KNOB and gaseous HCl. Bromine formation was determined through bromination reaction of acetanilide, added into the reaction mixture, and monitored by the gas chromatography mass spectrometry (GC-MS). It was found that this solvent-free oxidative bromination technique could also be used for bromination of several other activated aromatic compounds but bromination of deactivated aromatics under the same condition was not successful, pointing to the need for a catalyst. The developed solvent-free bromination method for aromatics has several benefits as there is no need for heating, the oxidizing agent is mild, and product purification procedure is simple. All mentioned features make this process quite perspective for synthetic applications.