DISTRIBUTION PROPERTIES OF BENZENE-DERIVATIVES .2. KINETICS OF DISTRIBUTION OF MONOSUBSTITUTED AND DISUBSTITUTED BENZENE-DERIVATIVES IN THE NORMAL-OCTANOL-WATER SYSTEM

The kinetics of distribution of 12 monosubstituted benzenes and 27 monosubstituted nitrobenzenes in the system n-octanol/water were investigated spectrophotometrically in the UV-VIS range at 6 temperatures between 293 and 313 K. From the experimental data the first-order rate constants k1 and k2 were evaluated graphically. Their temperature dependence was used to calculate the activation parameters DELTA-H not-equal and DELTA-S not-equal according to the Eyring equation. As excepted, the best correlations of log k values were obtained with HANSCH's hydrophobic substituent constants pi-B. In this way separate relationships could be found for 2-, 3- and 4- substituted nitrobenzenes. Furthermore, the activation parameters are also correlated with pi-B constants. These findings in connection with results of studies on isokinetic relationships indicate an enthalpy- and entropy-controlled influence of structure on the distribution behaviour of the given benzene derivatives.