A Theoretical Quantum Study of the Intramolecular Interactions and Chemical Reactivity of Polymorphs A and B of Famotidine in the Gas, DMSO, and Aqueous Phases.

In the present work, we have studied the intramolecular interactions and chemical reactivity of famotidine polymorphs A and B in the gas, DMSO, and aqueous phases at the X/def2TZVP level of theory (where X = wB97, wB97X, and wB97XD) and using the SDM solvation model. Also, the plane-wave density functional theory through the PSPW formulation was used to analyze the global reactivity parameters of famotidine. The geometry optimization of polymorphs A and B indicated extended and folded configurations, respectively. The results indicate that polymorph B exhibits a greater number of intramolecular interactions than polymorph A. Also, polymorph B is slightly more nucleophilic than polymorph A, which suggests better antiulcer activity by famotidine in a folded configuration.