NITRATION OF ALKYLBENZENES CATALYZED BY MERCURY(II), THALLIUM(III) AND LEAD(IV)

The nitration of alkylbenzenes, catalysed by mercury(II), has been stu died in a range of solvents. Using toluene as a model, catalysis, acco mpanied by a corresponding change in isomer ratio, is observed in a ni tric acid-acetic acid system and also when dilute nitric acid is emplo yed as the solvent. The results are consistent with a mercuration-nitr osodemercuration sequence occurring on the aromatic ring. Under more f orcing nitrating conditions catalysis is not observed. With other alky lbenzenes there is little evidence of catalysis though a complication, with compounds possessing benzylic hydrogen atoms, is that reaction o ccurs on the side chain. This may remove nitrosating species from the system. Thallium(IV) and lead(Iv), which are isoelectronic with mercur y(II), catalyse nitration without affecting the isomer distribution.