Synthesis and Spectroscopic and Gas Chromatographic Behavior of Isomeric Chlorinated Terphenyls

The synthesis and spectroscopic and chromatographic properties of 22 polychlorinated terphenyl (PCT) isomers are reported. Diazo coupling of a biphenylamine with an excess of a symmetrical chlorobenzene gave a single chloroterphenyl product; coupling with unsymmetrical chlorobenzenes gave mixtures which in some cases could be purified and identified by the wavelength of their characteristic ultraviolet absorption spectra. Chlorine substitution in the para position gives a characteristic bathochromic shift of the λ_max whereas substitution in the ortho positions gives a hypsochromic shift to these values. The gas-liquid chromatographic retention times of the PCT isomers increased with increasing chlorine content, whereas the relative molar electron capture responses tended to be highest with 4-chloro substitution and whereas ortho substitution (2 and 6 positions) gave the lowest response values. Availability of synthetic PCT isomers thus permits comparative evaluation of the environmental and biological impact of PCTs which have already been identified as pollutants.