C–H···O interaction: Difference between revisions

The C–H···O interaction was discovered in 1937 by [[Samuel Glasstone]]. Glasstone studied properties of mixtures of [[acetone]] with different [[Halogenation|halogenated derivative]]s of [[hydrocarbon]]s and realized that [[Molecular dipole moment|dipole moment]]s of these mixtures differ from dipole moments of pure substances. He explained this by establishing the concept of C–H···O interactions. The first crystallographic analysis of C-H ⋯O [[Hydrogen bond|hydrogen bonds]] were published by [[June Sutor]] in 1962.<ref>{{Cite journal|last=Schwalbe|first=Carl H.|date=2012|title=June Sutor and the C–H ··· O hydrogen bonding controversy|journal=Crystallography Reviews|volume=18|issue=3|pages=191–206|doi=10.1080/0889311x.2012.674945|s2cid=96289568 |issn=0889-311X}}</ref>

Similar to [[hydrogen bonds]], a C–H···O interaction involves [[Non-covalent interactions#Dipole-induced dipole|interactions of dipoles]] and therefore has [[Directionality (molecular biology)|directionality]].<ref>T. Steiner, G. R. Desiraju, Chem. Commun., 1998, 891.</ref> The directionality of a C–H···O interaction is usually defined by the angle ''α'' between the С, Н and О atoms, and the distance ''d'' between the O and C atoms. In a С–Н···О interaction, the angle ''α'' is in the range between 90 and 180°, and the distance ''d'' is usually smaller than 3.2 &nbsp;[[Angstrom|Å]].<ref>T. Steiner, CrystRev, 2003, 9, 2-3, 177.</ref> Bond strength is less than 1&nbsp;kcal/mol. In the case of [[aromatic]] C–H donors, C–H···O interactions are not linear due to influence of [[aromatic ring]] substituents near the interacting C-H group.<ref>D. Ž.Veljković, G. V. Janjić, S. D. Zarić, "Are C–H···O interactions linear? Case of aromatic CH donors.", CrystEngComm, 2011, 13, 5005. DOI:{{doi| 10.1039/C1CE05065F}}</ref><ref>J. Lj. Dragelj, G. V. Janjić, D. Ž. Veljković and S. D. Zarić, "Crystallographic and ab initio Study of Pyridine CH/O Interactions. Linearity of the interactions and influence of pyridine classical hydrogen bonds", CrystEngComm, (2013), vol. 15, 10481. DOI: 10.1039/C3CE40759D</ref> If aromatic molecules involved in С–Н···О interaction belong to the group of [[Polycyclic aromatic hydrocarbon|polycyclic aromatic hydrocarbons]], the strength of C–H···O interactions increases with the number of aromatic rings. <ref>{{Cite journal|date=2018-03-01|title=Strong CH/O interactions between polycyclic aromatic hydrocarbons and water: Influence of aromatic system size|journal=Journal of Molecular Graphics and Modelling|language=en|volume=80|pages=121–125|doi=10.1016/j.jmgm.2017.12.014|pmid=29331729|issn=1093-3263|last1=Veljković|first1=Dušan Ž.|url=http://cherry.chem.bg.ac.rs/handle/123456789/2815}}</ref>