Tautomer


Tautomers (/ˈtɔːtəmər/)[1] are structural isomers (constitutional isomers) of chemical compounds that readily interconvert.[2][3][4][5] This reaction commonly results in the relocation of a hydrogen atom. Tautomerism is for example relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life.

The concept of tautomerizations is called tautomerism. Tautomerism is also called desmotropism. The chemical reaction interconverting the two is called tautomerization.

Care should be taken not to confuse tautomers with depictions of "contributing structures" in chemical resonance. Tautomers are distinct chemical species and can be identified as such by their differing spectroscopic data,[6] whereas resonance structures are merely convenient depictions and do not physically exist.

Contents

Examples


Tautomerization is pervasive in organic chemistry. It is typically associated with polar molecules and ions containing functional groups that are at least weakly acidic. Most common tautomers exist in pairs, which means that the hydrogen is located at one of two positions, and even more specifically the most common form involves a hydrogen changing places with a double bond: H−X−Y=Z ⇌ X=Y−Z−H. Common tautomeric pairs include:[7]

Prototropy


Prototropy is the most common form of tautomerism and refers to the relocation of a hydrogen atom.[8] Prototropic tautomerism may be considered a subset of acid-base behavior. Prototropic tautomers are sets of isomeric protonation states with the same empirical formula and total charge. Tautomerizations are catalyzed by:[citation needed]

Two specific further subcategories of tautomerizations:

Valence tautomerism


Valence tautomerism is a type of tautomerism in which single and/or double bonds are rapidly formed and ruptured, without migration of atoms or groups.[10] It is distinct from prototropic tautomerism, and involves processes with rapid reorganisation of bonding electrons.

A pair of valence tautomers with formula C6H6O are benzene oxide and oxepin.[10][11]

Other examples of this type of tautomerism can be found in bullvalene, and in open and closed forms of certain heterocycles, such as organic azides and tetrazoles,[12] or mesoionic münchnone and acylamino ketene.

Valence tautomerism requires a change in molecular geometry and should not be confused with canonical resonance structures or mesomers.

See also


References


  1. ^ "tautomer" . Oxford Dictionaries - English. Archived from the original on 2018-02-19.
  2. ^ Antonov L (2013). Tautomerism: Methods and Theories (1st ed.). Weinheim, Germany: Wiley-VCH. ISBN 978-3-527-33294-6.
  3. ^ Antonov L (2016). Tautomerism: Concepts and Applications in Science and Technology (1st ed.). Weinheim, Germany: Wiley-VCH. ISBN 978-3-527-33995-2.
  4. ^ Smith MB, March J (2001). Advanced Organic Chemistry (5th ed.). New York: Wiley Interscience. pp. 1218–1223. ISBN 978-0-471-58589-3.
  5. ^ Katritzky AR, Elguero J, et al. (1976). The Tautomerism of heterocycles . New York: Academic Press. ISBN 978-0-12-020651-3.
  6. ^ Smith, Kyle T.; Young, Sherri C.; DeBlasio, James W.; Hamann, Christian S. (27 January 2016). "Measuring Structural and Electronic Effects on Keto–Enol Equilibrium in 1,3-Dicarbonyl Compounds". Journal of Chemical Education. 93 (4): 790–794. doi:10.1021/acs.jchemed.5b00170 .
  7. ^ a b Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 978-0-471-72091-1
  8. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Tautomerism ". doi:10.1351/goldbook.T06252
  9. ^ Roman M. Balabin (2009). "Tautomeric equilibrium and hydrogen shifts in tetrazole and triazoles: Focal-point analysis and ab initio limit". J. Chem. Phys. 131 (15): 154307. Bibcode:2009JChPh.131o4307B . doi:10.1063/1.3249968 . PMID 20568864 .[non-primary source needed][better source needed]
  10. ^ a b IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "valence tautomerization ". doi:10.1351/goldbook.V06591.html
  11. ^ E. Vogel and H. Günther (1967). "Benzene Oxide-Oxepin Valence Tautomerism". Angewandte Chemie International Edition in English. 6 (5): 385–401. doi:10.1002/anie.196703851 .
  12. ^ Lakshman Mahesh K., Singh Manish K., Parrish Damon, Balachandran Raghavan, Day Billy W. (2010). "Azide−Tetrazole Equilibrium of C-6 Azidopurine Nucleosides and Their Ligation Reactions with Alkynes" . The Journal of Organic Chemistry. 75 (8): 2461–2473. doi:10.1021/jo902342z . PMC 2877261 . PMID 20297785 .CS1 maint: multiple names: authors list (link)

External links









Categories: Isomerism




Information as of: 28.06.2021 09:15:20 CEST

Source: Wikipedia (Authors [History])    License : CC-BY-SA-3.0

Changes: All pictures and most design elements which are related to those, were removed. Some Icons were replaced by FontAwesome-Icons. Some templates were removed (like “article needs expansion) or assigned (like “hatnotes”). CSS classes were either removed or harmonized.
Wikipedia specific links which do not lead to an article or category (like “Redlinks”, “links to the edit page”, “links to portals”) were removed. Every external link has an additional FontAwesome-Icon. Beside some small changes of design, media-container, maps, navigation-boxes, spoken versions and Geo-microformats were removed.

Please note: Because the given content is automatically taken from Wikipedia at the given point of time, a manual verification was and is not possible. Therefore LinkFang.org does not guarantee the accuracy and actuality of the acquired content. If there is an Information which is wrong at the moment or has an inaccurate display please feel free to contact us: email.
See also: Legal Notice & Privacy policy.