Structure Analyses of Two Crystal Forms of Paroxetine Hydrochloride

Two crystal forms of (−)-trans-4-(p-fluorophenyl)-3-(3,4-methylenedioxyphenoxymethyl)piperidine hydrochloride salt (paroxetine HCl) have been analyzed by X-rays. One form (Form I) is obtained as a hemihydrate and the other (Form II) is crystallized as the propan-2-ol solvate. The crystal of Form I belongs to the monoclinic system and the space group is P21. The unit-cell dimensions are; a = 14.5888(10), b = 10.1591(7), c = 13.0255(10) Å, β = 107.095(3)°, and V = 1845.2(2) Å3. There are two crystallographically independent protonated paroxetine molecules with different conformations and chloride anions, and one water molecule in an asymmetric unit. The crystal of Form II also belongs to the monoclinic system and the space group is P21. The unit-cell dimensions are; a = 11.6504(7), b = 5.7374(3), c = 16.4107(10) Å, β = 90.959(2)°, and V = 1096.79(11) Å3. There are one protonated paroxetine molecule, one chloride anion, and one solvent propan-2-ol molecule in an asymmetric unit. The protonated paroxetine molecule in Form II has a different conformation from those in Form I. The solvent propan-2-ol molecule is disordered in the channel formed by paroxetine molecules and chloride anions. The crystal was easily decomposed in open air at room temperature because the propan-2-ol molecules are easily released through the channel.