Thermodynamics of partitioning of propranolol in some organic solvent/buffer systems

Abstract

Propranolol (PPN) partitioning thermodynamics was studied at five temperatures in several solvent/buffer systems, namely, cyclohexane (CHAV), octanol (ROHAV), isopropyl myristate (IPMAV), and chloroform (CLFAV). In all cases, the mole fraction partition coefficients (Ko/wX) were greater than unity; therefore, the standard Gibbs energies of transfer are negative, indicating a high affinity of PPN for all organic media evaluated. Ko/wX values were approximately 57 times higher in the ROHAV system with respect to CHAV, thus indicating a high degree of hydrogen bonding contribution to partitioning, whereas in the case of the PMAV and CLFAV systems, the Ko/wX values were similar to those observed in ROHAV. In all cases, standard enthalpies and entropies of transfer of PPN from water to organic solvents were positive. These results indicate some degree of participation of the hydrophobic hydration in the PPN partitioning processes.