McLafferty rearrangement

The McLafferty rearrangement is an organic reaction seen in mass spectrometry. A mass spectrometer breaks apart the molecule being studied. The molecule breaks apart in consistent ways that chemists can predict. Most of the time, a carbon-carbon bond breaks and the atoms do not jump across the break between the fragments. The McLafferty rearrangement is an example of a hydrogen atom jumping to the other fragment as a part of the process of the bond breaking. It happens in an organic molecule containing a keto-group.

The reaction

The American chemist Fred McLafferty was the first to describe the reaction in 1959.^[1][2][3]

An example of the McLafferty rearrangement

The keto-group undergoes β-cleavage, with the gain of the γ-hydrogen atom. This rearrangement may take place by a radical or ionic mechanism.

Related pages

• α-cleavage

References

1. F. W. McLafferty (1959). "Mass Spectrometric Analysis. Molecular Rearrangements". Anal. Chem. 31 (1): 82–87. doi:10.1021/ac60145a015.
2. Gross ML (2004). "Focus in honor of Fred McLafferty, 2003 Distinguished Contribution awardee, for the discovery of the "McLafferty Rearrangement"". J. Am. Soc. Mass Spectrom. 15 (7): 951–5. doi:10.1016/j.jasms.2004.05.009. PMID 15234352. S2CID 42341600.
3. Nibbering NM (2004). "The McLafferty rearrangement: a personal recollection". J. Am. Soc. Mass Spectrom. 15 (7): 956–8. doi:10.1016/j.jasms.2004.04.025. PMID 15234353. S2CID 22883437.

Further reading

• International Union of Pure and Applied Chemistry. "McLafferty rearrangement". Compendium of Chemical Terminology Internet edition.

Other websites

• Fred McLafferty Faculty Webpage at Cornell University