Definition of the Hydrogen Bond (IUPAC Recommendations 2011) (Report‪)‬

1. PREAMBLE The task group recommends the definition given here for the hydrogen bond. The short definition is followed by a list of experimental and/or theoretical criteria, which can be used as evidence for the presence of the hydrogen bond. Finally, some characteristics that are typical of hydrogen-bonded systems are given. A brief explanation of the terms used is provided after the definition. Moreover, several footnotes (indicated by F#) have been added, and these are given at the end. These footnotes are intended to give more explanation for the sake of clarity and completeness. The task group has also produced a comprehensive technical report, which appears elsewhere in this issue of Pure and Applied Chemistry [1]. This report provides a summary of the past work on hydrogen bonding and also the rationale for the proposed definition.