General procedure for the synthesis of 4-bromo-4'-propylbiphenyl from 4-n-propylbiphenyl: To a reaction flask was added 1 equiv. of 4-n-propylbiphenyl (Compound 5), methylene chloride (the fifth organic solvent), and 0.2 equiv. of ferric chloride, wherein the ratio of methylene chloride to 4-n-propylbiphenyl by weight was 5:1. The mixture was stirred thoroughly, 1.15 equiv. of liquid bromine was added slowly, and the reaction temperature was The reaction temperature was maintained at 25 °C and the reaction time was 18 hours. Upon completion of the reaction, the reaction was quenched by the addition of 15% aqueous sodium hydroxide, stirred and left to separate. The organic phase was washed twice with water to remove the aqueous phase. Subsequently, the organic phase was dried to give the crude product 4-bromo-4'-propylbiphenyl (compound 6). The crude product was pulped in methanol, filtered and dried to give 4-bromo-4'-propylbiphenyl (compound 6) as a white solid in 77% yield.
