Tautomerism in acyl-pyrazolones and in a novel photolysis product—importance and impact of the accurate localization of hydrogen atoms in crystal structures

Lorraine A. Malaspina, Allan H. White, Dieter Wege, Michael B. Tolmie, Brian W. Skelton, Simon Grabowsky

Research output: Contribution to journalArticle

2 Citations (Scopus)


Acyl-pyrazolones exist in four different tautomeric forms (two keto and two enol) in crystal structures. Routine crystal structure refinements using an independent atom model and routine isolated-molecule calculations fail in locating the mobile hydrogen atoms accurately in 22 investigated acyl-pyrazolone examples. However, a combination of both within the framework of quantum crystallography represented by the method of Hirshfeld atom refinement accurately locates the mobile hydrogen atom in a resonance-assisted hydrogen bond of title compound 3, a novel photolysis product. The impact of the hydrogen atom position on the resonance system of the non-hydrogen framework of the various tautomers is discussed, and the importance of intermolecular interactions for the positioning of the hydrogen atom is highlighted.

Original languageEnglish
Pages (from-to)1343–1357
Number of pages15
JournalStructural Chemistry: computational and experimental studies of chemical and biological systems
Issue number5
Publication statusPublished - Oct 2017


Cite this