Synthesis, Characterization and Solubility Determination of 6-Phenyl-pyridazin-3(2 H )-one in Different Pharmaceutical Solvents

The current research work proposed the solubility data and solution thermodynamic properties of the cardiovascular agent 6-phenylpyridazin-3(2 H )-one [PPD] in twelve pharmaceutical solvents at “ T = 298.2 K to 318.2 K” and “ p = 0.1 MPa”. The measured solubilities of PPD were regressed well with “van’t Hoff and Apelblat models”. The solid phases of pure and equilibrated PPD were characterized using differential scanning calorimetry and powder X-ray differactometry, and the results suggested no transformation of PPD into solvates/hydrates/polymorphs after equilibrium. The solubilities of PPD in a mole fraction at “ T = 318.2 K” were noted at a maximum in dimethyl sulfoxide (DMSO, 4.73 × 10 −1 ), followed by polyethylene glycol-400 (PEG-400, 4.12 × 10 −1 ), Transcutol ® (3.46 × 10 −1 ), ethyl acetate (EA, 81 × 10 −2 ), 2-butanol (2.18 × 10 −2 ), 1-butanol (2.11 × 10 −2 ), propylene glycol (PG, 1.50 × 10 −2 ), isopropyl alcohol (IPA, 1.44 × 10 −2 ), ethylene glycol (EG, 1.27 × 10 −2 ), ethanol (8.22 × 10 −3 ), methanol (5.18 × 10 −3 ) and water (1.26 × 10 −5 ). Similar tendencies were also noted at other studied temperatures. The results of the “apparent thermodynamic analysis” showed an endothermic and entropy-driven dissolution of PPD in all pharmaceutical solvents. The results of the activity coefficients suggested a maximum interaction at the molecular level in PPD-DMSO, PPD-PEG-400 and PPD-Transcutol, compared with other combination of the solute and solvents.