Isomer specific synthesis using the Suzuki-coupling. Polychlorinated terphenyls as standards for environmental analysis

Defined polychlorinated terphenyl (PCT) single congeners as reference standards are the prerequisite for the development of analytical methods for their determination and quantification in the environment. The selective synthesis of PCTs for environmental analytical purposes by application of the Suzuki-coupling reaction is described. Under easily modified standard reaction conditions of this coupling process the PCTs can be obtained by reaction of benzeneboronic acids with dibromobenzenes mostly in good yields, as described by the synthesis of following PCT congeners: p-PCT (3,3″,5,5″-tetrachloro-, 2,2″,4,4″-tetrachloro-, 2′,3,3″,5,5″-pentachloro-); m-PCT (3,3″,5,5″-tetrachloro-) and o-PCT (3,3″,5,5″-tetrachloro-). The terphenyl congeners were characterized by NMR (1H, 13C)- and FT-IR-spectroscopy. Their purity was checked by GC/MS analysis. The experimental and quantum-chemically calculated FT-IR-spectra were compared and it was shown, that the determination of the chlorine substitution pattern in the terphenyl congeners by their typical absorption spectra is possible.