Authentication of 5-bromo-3-chloro-1,2-dimethoxybenzene by NMR and GC-MS. This compound was synthesized from 4-bromo-2-chloro-6-fluoroanisole via aromatic nucleophilic substitution in the presence of sodium methoxide and is a precursor for the preparation of 3,3'-dichloro-4,5-dimethoxy-biphenyl, a derivative of PCB 11 (3,3'-dichlorobiphenyl).