US EPA

2751278 

Technical Report 

The relationship between chemical structures of chlorophenols and their biological activities 

Matsumura, A 

1972 

HAPAB/72/00799 

Igaku 

Jap. J. Ind. Health 

HAPAB The author chose three di-, two tri-, one tetra-, and one pentachlorophenol as material and studied the relationship between chemical structures and their effects on oxidative phosphorylation in rat liver mitochondria. The effects were studied by a manometric method; ATP-ase activity of intact mitochondria being estimated by net release of phosphate from ATP; dissociation constants for chlorophenols being measured by comparison of absorption spectra in solution of different pH or by potentiometric titration. It was found that all compounds were potent uncouplers for oxidative phosphorylation because of their dissociation of respiration of mitochondria from inorganic phosphate uptake and their activation of latent ATPase of freshly prepared mitochondria. As the number of substituted chlorine atoms in the benzene ring is increased, the impairment of oxidative phosphorylation is augmented. The addition of a chlorine atom seemed to decrease the dissociation constant, pK, however, the definite pK was dependent on the position of the substituent. Chlorophenols were grouped into two classes according to their equi-effective concentrations and pK values. Within each group there is an inverse linear relationship between equi-effective concentration and pK value. It seems probable that the anion produced by ionization of 2,6-positions cannot react with some intermediates of phosphorylation mechanisms by virtue of the steric or electronic interference by the ortho-chlorine atom. 1972