Dioxin Precursors: NQR Studies of Group 1 and Related 2,6-Dichlorophenolate and 2,4,6-Trichlorophenolate Salts

Abstract

The 81 Br and 35 C1 NQR spectra of anhydrous Group 1, tetraalkylammonium, and thallium(I) 2,6-dichlorophenolates, 2,4,6-trichlorophenolates, and 4-bromo-2,6-dichlorophenolates were searched for evidence of solid-state cation-organochlorine interactions that might, for example, be (in part) responsible for the difference in the thermal decomposition reactions of these salts (to give the supertoxic environmental pollutants, the polychlorinated dibenzodioxins) versus those of the corresponding Group 11 chlorophenolate complexes, which do not decompose to dioxins.For cations ranging in size from tetraethylammonium to potassium, the total range of 35 C1 NQR frequencies in 2,6-dichlorophenolate and 2,4,6-trichlorophenolate salts is only 1.401 MHz, which, although larger than the 0.7 MHz range likely in molecular chlorocarbons, is smaller than in individual chlorophenolates of copper(I) and silver(I) (up to 2.0 MHz). In sodium and thallium(I) 2,4,6-trichlorophenolates substantially large frequency shifts (ca. 2.0 MHz) occur, to higher frequencies for the para-chlorines and lower frequencies for the ortho-chlorines (Na only). These disappear even in closely related compounds and show a pattern that seems unrelated to the decomposition products of the chlorophenolates.

Nuclear Quadrupole Resonance spectroscopy in studies of biologically active molecular systems—a review

“…Encouraging results were obtained for a group of phenoxyl herbicides-derivatives of phenoxyacetic acid substituted at positions 2, 4 and 5 [2,4-dichlorophenoxyacetic acid (2,4-D); 4-chloro-2-methyl phenoxyacetic acid (MCPA); 2,4,5-trichloro phenoxyacetic acid (2,4,5-T)] and their metabolites (2,4-dichlorophenol, 4-chloro-2-methylphenol and 2,4,5-trichlorophenol). The 35 Cl NQR quadrupole coupling constants [55][56][57][58] and lethal doses LD 50 [35], percentage of erythrocyte hemolysis and the number of free SH groups responsible for damage to the membrane proteins [58] for the hitherto studied herbicides were taken into account. These data indicated that the toxicity of phenoxyl herbicides was correlated with 35 Cl NQR frequencies.…”