The proton chemical shifts of polychlorinated biphenyls

Abstract

A 220 MHz NMR spectrometer has been used to identify the structure of polychlorinated biphenyls (PCBs). The proton chemical shifts and approximate coupling constants of PCBs fractionated from Aroclor 1254 are given in the text. The spectra of model compounds are included in the supplement. The chemical shifts are also tabulated according to the ring substitution pattern, when it can be seen that the shifts change systematically with the degree of both the total ring substitution and the substitution in the positions 'ortho' to the bridging bond between the rings.

Toxicity and persistence of PCB homologs and isomers in the avian system

“…Retention times were calculated for each chromatogram relative to the greatest peak (Table I, peak 9). The structures given in the last column of Table I are those assigned by Sissons and Welti (11971) and Welti and Sissons (1972) to their peaks on a SCOT column. Assignment of these structures to the peaks in our chromatogram is made on the basis of the close cmrespondence of relative retention times shown in Table I and also by considering the relative proportions of the peaks (Figure 3, Table II), which appear to be identical to those of Sissons and Welti (1971).…”

“…and Welti and Sissons (1972)have made an exhaustive study of PCBs using the hydrocarbon phase Apiezon L, which gives the largest number of peaks of any stationary phase. Employing support coated open tubular (SCOT) columns and using 220 MHz nuclear magnetic resonance (NMR) and mass spectrometry, combined with Kovat's Retention Indices and chemical synthesis, they have identified 76 individual PCBs from the Aroclor mixtures.…”

1H NMR parameters of chlorinated biphenyls

“…represent the repulsive contribution from two chlorine atoms substituted on the biphenyl ring in a crowded relationship. The calculations using Eqns (1) and (2) were carried out by the least-squares method, and the results obtained for the 'H shifts and the coupling constants are shown in Tables 3 and 4, respectively. The agreements are satisfactory, and are particularly good for the observed and calculated values of the coupling constants.…”

A multi-national company, the public and the environment

“…Now, the analysts have to be prepared to identify environmental contaminants such as organochlorine pesticides (Sissons, Telling & Usher 1968), organophosphorus insecticides (Sissons & Telling 1970) and polychlorinated biphenyls (Welti & Sissons 1972), which could be present in the raw materials used by Unilever. Considerable research effort goes into devising new and even more sensitive or more rapid methods of idenitfying these and other contaminants of food (Bryce & Telling 1972).…”