RELATION BETWEEN THE CHEMICAL STRUCTURES OF CHLOROPHENOLS AND THEIR DISSOCIATION-CONSTANTS AND PARTITION-COEFFICIENTS IN SEVERAL SOLVENT-WATER SYSTEMS

The partition coefficients and dissociation constants (as pK(a)) of chlorophenols were determined, using n-heptane and n-octane as non-hydrogen bonding solvents, and I-octanol and n-heptane containing lecithin as hydrogen bonding solvents. The coefficients of chlorophenols in n-heptane-water were almost the same values as those in n-octane-water. A good correlation of r = 0.996 was observed between the coefficient in I-octanol-water and that in n-heptane containing lecithin-water. However, the correlation between the coefficient in n-octane-water and that in I-octanol-water was a little low (r = 0.885) compared with the above value, and that between n-heptane-water and n-heptane containing lecithin-water was also a little low (r = 0.890). The partition coefficients of chlorophenols in the solvent-water systems increased with increasing number of chlorine atoms. In chlorophenols having the same number of chlorine atoms, their partition coefficients in hydrogen bonding solvent-water decreased in the order of non-, mono- and di-orthochlorophenols, whereas the coefficients in non-hydrogen bonding solvent-water increased in the above order. This fact must be attributed to the formation of intramolecular hydrogen bonding between the chlorine atom substituted at the ortho-position and the OH group in the chlorophenols. The pK(a) values of chlorophenols decreased with increasing number of chlorine atoms, and also with the closing of the chlorine atom position to the OH group in chlorophenols having the same number of chlorine atoms.