Ozonolysis



Ozonolysis is the cleavage of an oxygen.[1][2][3] The outcome of the reaction depends on the type of multiple bond being oxidized and the workup conditions.

Ozonolysis of alkenes

Alkenes can be oxidized with ozone to form alcohols, oleic acid on an industrial scale.

A widely used alternative method[5] for the ozonolysis of symmetrical alkenes allows differentially terminated hydrocarbons to be generated:

  • with O3/MeOH/CH2Cl2; acetal termini
  • with O3/MeOH/CH2Cl2; esters and aldehyde termini
  • with O3/MeOH/CH2Cl2; TsOH; Ac2O, Et3N, methyl ester and dimethyl acetal termini.

An example is the ozonolysis of eugenol converting the terminal alkene to an aldehyde [6]:

Reaction mechanism

In the generally accepted mechanism proposed by Rudolf Criegee in 1953,[7] the alkene and ozone form an intermediate molozonide in a 1,3-dipolar cycloaddition. Next, the molozonide reverts to its corresponding carbonyl oxide (also called the Criegee intermediate) and aldehyde or ketone in a retro-1,3-dipolar cycloaddition. The oxide and aldehyde or ketone react again in a 1,3-dipolar cycloaddition or produce a stable ozonide intermediate (a trioxolane).

Evidence for this mechanism is found in benzaldehyde reacts with carbonyl oxides, the label ends up exclusively in the ether linkage of the ozonide.[8] There is still dispute over whether the molozonide collapses via a concerted or radical process; this may also exhibit a substrate dependence.

History

Ozonolysis was invented by Christian Friedrich Schönbein in 1840. Before the advent of modern spectroscopic teechniques, it was an important method for determining the structure of organic molecules. Chemists would ozonize an unknown alkene to yield smaller and more identififable fragments. The ozonolysis of alkenes is sometimes referred to as "Harries Ozonolysis," because some attribute this reaction to Carl Dietrich Harries.

Ozonolysis of alkynes

Ozonolysis of carboxylic acids.

References

  1. ^ Claus, R. E.; Schreiber, S. L. Org. Syn., Coll. Vol. 7, p.168 (1990); Vol. 64, p.150 (1986). (Article)
  2. ^ Bailey, P. S.; Erickson, R. E. Org. Syn., Coll. Vol. 5, p.489 (1973); Vol. 41, p.41 (1961). (Article)
  3. ^ Tietze, L. F.; Bratz, M. Org. Syn., Coll. Vol. 9, p.314 (1998); Vol. 71, p.214 (1993). (Article)
  4. ^ (Org Lett 2006, 8, 3199-3201)
  5. ^ (Schreiber, Org Syn v64)
  6. ^ Using Ozone in Organic Chemistry Lab: The Ozonolysis of Eugenol Bruce M. Branan, Joshua T. Butcher, and Lawrence R. Olsen Journal of Chemical Education 2007 1979
  7. ^ Criegee, R. Angew. Chem. Int. Ed. Engl. 1975, 87, 745-752. (doi:10.1002/anie.197507451)
  8. ^ The Mechanism of Ozonolysis Revisited by 17O-NMR Spectroscopy Geletneky, C.; Berger, S. Eur. J. Org. Chem. 1998, 1625-1627. (Abstract)
  9. ^ Bailey, P. S., chapter 2, in (1982) Ozonation in Organic Chemistry. Volume II: Nonolefinic Compounds. New York: Academic Press. ISBN 0120731029. 
  10. ^ Cremer, D.; Crehuet, R.; Anglada, J. (2001). "The Ozonolysis of Acetylene-A Quantum Chemical Investigation". J. Am. Chem. Soc. 123 (25): 6127–6141. doi:10.1021/ja010166f.
 
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