(3S, 4R)-4-(4-fluorophenyl)-3-(hydroxymethyl)piperidinium chloride

The title compound, C12H17FNO+center dot Cl-, is a degradation impurity of paroxetine hydrochloride hemihydrate (PAXIL), an antidepressant belonging to the group of drugs called selective serotonin reuptake inhibitors (SSRIs). Similar to the paroxetine hydrochloride salt with protonation having taken place on the basic piperidine ring, the degradation impurity also exists as the hydrochloride salt. The cyclic six-membered piperidinium ring adopts a chair conformation with the hydroxymethyl and 4-fluorophenyl groups in the equatorial positions. The ions form a tape along the b axis through charge-assisted N+-H center dot center dot center dot Cl- hydrogen bonds; these tapes are connected by O-H center dot center dot center dot Cl- hydrogen bonds along the a axis.