In chemistry, a C–H···O interaction is occasionally described as a special type of weak hydrogen bond. These interactions frequently occur in the structures of important biomolecules like amino acids, proteins, sugars, DNA and RNA.[1][2]

History

The C–H···O interaction was discovered in 1937 by Samuel Glasstone. Glasstone studied properties of mixtures of acetone with different halogenated derivatives of hydrocarbons and realized that dipole moments 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 bonds were published by June Sutor in 1962.[3]

Properties

Similar to hydrogen bonds, a C–H···O interaction involves interactions of dipoles and therefore has directionality.[4] 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 Å.[5] Bond strength is less than 1 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.[6][7] If aromatic molecules involved in С–Н···О interaction belong to the group of polycyclic aromatic hydrocarbons, the strength of C–H···O interactions increases with the number of aromatic rings.[8]

C–H···O interactions can be important in drug design, being present in structures of therapeutic proteins,[9][10] and nucleic acids.[11]

O-H···C and N-H···C type interactions could also play a significant role and were first analyzed in 1993.[12]

References

  1. ↑ G. R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and Biology, 1999, OxfordUniversity Press, Oxford (1999).
  2. ↑ M. S. Weiss, Trends Biochem. Sci., 2001, 26, 521.
  3. ↑ Schwalbe, Carl H. (2012). "June Sutor and the C–H ··· O hydrogen bonding controversy". Crystallography Reviews. 18 (3): 191–206. doi:10.1080/0889311x.2012.674945. ISSN 0889-311X. S2CID 96289568.
  4. ↑ T. Steiner, G. R. Desiraju, Chem. Commun., 1998, 891.
  5. ↑ T. Steiner, CrystRev, 2003, 9, 2-3, 177.
  6. ↑ 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:10.1039/C1CE05065F
  7. ↑ 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
  8. ↑ Veljković, Dušan Ž. (2018-03-01). "Strong CH/O interactions between polycyclic aromatic hydrocarbons and water: Influence of aromatic system size". Journal of Molecular Graphics and Modelling. 80: 121–125. doi:10.1016/j.jmgm.2017.12.014. ISSN 1093-3263. PMID 29331729.
  9. ↑ K. Ramanathan, V. Shanthi, R. Sethumadhavan, Int J Pharm Pharm Sci, 2011, 3, 3, 324.
  10. ↑ D. P. Malenov, G. V. Janjić, D. Ž. Veljković, S. D. Zarić, "Mutual influence of parallel, CH/O, OH/π and lone pair/π interactions in water/benzene/water system", Computational and Theoretical Chemistry, (2013), vol. 1018, 59 - 65. DOI: 10.1016/j.comptc.2013.05.030
  11. ↑ D. Ž Veljković, V. B Medakovic, J. M. Andric and S. D. Zaric, "C–H/O interactions of nucleic bases with water molecule. Crystallographic and quantum chemical study.", CrystEngComm, 2014., DOI: 10.1039/C4CE00595C
  12. ↑ M.A. Viswamitra, R. Radhakrishnan, J. Bandekar, G. R. Desiraju, "Evidence for O-H···C and N-H···C hydrogen bonding in crystalline alkynes, alkenes, and aromatics", J. Am. Chem. Soc. 1993, 115, 4868-4869.DOI:10.1021/ja00064a055
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