Synthesis and Characterization of Stable Isotope Labeled 3,3',4,4'-Tetrachlorobiphenyl-D₆

A new synthetic method of the stable isotope labeled 3,3',4,4'-tetrachlorobiphenyl-D₆ was investigated. The synthesis of 3,3',4,4'-tetrachlorobiphenyl-D₆ is based on 1,2-dichlorobenzene-D₄ as the labeling precursor through three steps of catalyzed borylation, iodination, Suzuki coupling reaction. According to the amount of 1,2-dichlorobenzene-D₄, the yield of 3,3',4,4'-tetrachlorobiphenyl-D₆ was 72.85%. The structure of the target product was characterized by ¹H-NMR, gas-mass spectrometry and gas chromatography. The chemical purity of 3,3',4,4'-tetrachlorobiphenyl-D₆ was 99.54%, and the abundance of deuterium isotope was 98.38 atom%D. It can be used as the isotope internal standard for the determination of polychlorinated biphenyls.