Hypervalency in organic crystals: A case study of the oxicam sulfonamide group

Christian Tantardini, Elena V. Boldyreva, Enrico Benassi

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The theoretical charge density of the active pharmaceutical ingredient piroxicam (PXM) was evaluated through density functional theory with a localized basis set. To understand the electronic nature of the sulfur atom within the sulfonamide group, a highly ubiquitous functional group in pharmaceutical molecules, a theoretical charge density study was performed on PXM within the framework of Bader theory. Focus is on developing a topological description of the sulfur atom and its bonds within the sulfonamide group. It was found that sulfur d-orbitals do not participate in bonding. Instead, the existence of a strongly polarized ("ionic") bonding structure is found through a combined topological and natural bonding orbital analysis. This finding is in stark contrast to long-held theories of the bonding structure of organic sulfonamide and has important implications for the parametrization of calculations using classical approaches. (Chemical Equation Presented).

Original languageEnglish
Pages (from-to)10289-10296
Number of pages8
JournalJournal of Physical Chemistry A
Issue number51
Publication statusPublished - 8 Dec 2016
Externally publishedYes


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