Distribution of Picric Acid into Various Diluents

Extraction constants, defined as K-ex = [HPic](o)/[H+][Pic(-)], for picric acid (HPic) into ten diluents were spectrophotometrically determined at 298K, where the subscript "o" refers to an organic (o) phase which is composed of the diluent. Their values for the HPic extraction into benzene and chloroform were fairly consistent with those reported before. From the K-ex values, distribution constants (K-D,K-HPic) of HPic into the o phases were estimated using the thermodynamic relation K-ex = K-D,K-HPic,K-HPic, where K-HPic corresponds to a protonation constant of Pic(-) in water. Thereby, contributions of functional groups, such as -Cl and -CH3, involved in the diluents molecules to K-D,K-HPic were discussed. The same discussion was also applied for the distribution of the ion pair, composed of CdPic(2) and 18-crown-6 ether, into the diluents.