RESUMO
In the course of the development of a new and reliable analytical method for the PCT, a group of environmental contaminants, six coplanar terphenyl congeners were synthesized and characterized by means of spectroscopic methods. These congeners are 3,3â³,4,4â³,5-pentachloro-p-terphenyl, 3,3â³,4,5,5â³-pentachloro-p-terphenyl, 3,3â³,4,5â³-tetrachloro-m-terphenyl, 3,3â³,4,4â³,5-pentachloro-m-terphenyl, 3,3â³,5,5',5â³-pentachloro-m-terphenyl, and 3,3â³,4,4â³,5,5â³-hexachloro-m-terphenyl. A combination of silica gel column chromatography and preparative NP-HPLC was successfully applied for the first time for the isolation of especially the asymmetrically chlorinated target compounds from product mixtures of the syntheses. For the 29 coplanar, tetra- to heptachlorinated meta- and para-indicator congeners which are envisaged to be used within the analytical method, a simplified systematic nomenclature is suggested. Furthermore, calculation results for all torsion angles of the preferred conformations of the substances are given. The practical relevance of the calculated conformation optima is exemplarily demonstrated by the chromatographic behavior of the PCT compounds.
Assuntos
Poluentes Ambientais/análise , Poluentes Ambientais/síntese química , Compostos de Policloroterfenilo/análise , Compostos de Policloroterfenilo/síntese química , Poluentes Ambientais/química , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Compostos de Policloroterfenilo/química , Padrões de Referência , Relação Estrutura-AtividadeRESUMO
A CD(3) group close in space to (but many bonds distant from) a carbon atom A causes a substituent effect on the chemical shift of C(A) that is algebraically smaller than the effect of a CH(3) group, in agreement with the notion of shorter C-D relative to C-H bonds. Hence, the deuterium isotope effect of CD(3) upon delta(C(A)) is shielding when the substituent effect is deshielding, and vice versa.