Relationships between crystal structures and thermodynamic properties of phenylbutazone solvates

Abstract

The relationships between the crystal structures and the thermodynamic properties of six phenylbutazone solvates were studied. From the crystal structures the free volume available to the solvent molecules, V_asm, the packing density of the solvent in the solvate channels, K_chan, and the lattice energy of each solvate, E_lattice, were calculated and the intermolecular interactions in the solvates were identified. From the measured equilibrium vapor pressure of the solvent above each solvate and above each liquid solvent, the standard free energy, ΔG_des, enthalpy, ΔH_des, and entropy, ΔS_des, of desolvation of each solvate were calculated. Linear correlations between K_chan and ΔS_des, between E_lattice and ΔH_des, and between V_asm and both ΔS_des and ΔH_des suggest that similar crystal structures afford smooth monotonic variations in intermolecular interaction energies.