The equilibrium constants for the reaction of 2,6-dichloro-4-
-nitrophenol, 2,6-dinitrophenol, 2,5-dinitrophenol and 2,4-dinitrophenol
with some aliphatic amines of different structures have been
determined spectrophotometrically in chlorobenzene, ethyl acetate
and carbon tetrachloride as solvents. The data show that such
reactions in inert solvents lead essentially to ion-pairs of the type
BH+ ... A- where, HA and B represent the phenol and ·amine
molecule, respectively. This conclusions was found to be in agreement
with that obtained by other workers. In chlorobenzene as a
solvent, the basic strengths fall in the order mono < di- < tri-n-
. -butyl amine, while in ethyl acetate the order of basic strengths
becomes: mono-> di-> tri-n-butyl amine. These results are discussed
from the point of view of solvation as an important role in
the determination of the relative strengths of butylamines, as well
as the extent to which dinitrophenols are affected by chelation
between the phenolic OH and ortho-nitro group. However, in chlorobenzene
and ethyl acetate as solvents, the relative basic strengths
of pyridine and aniline derivatives remain independent of the
solvent when bromophenol blue is used as a reference acid. The
of KBH+A- values for aniline derivatives proved to be more suitable
for judging the effect of the substituent than the basic strength in
aqueous solution
