McLafferty rearrangement

The McLafferty rearrangement is a reaction observed in mass spectrometry during the fragmentation or dissociation of organic molecules. It is sometimes found that a molecule containing a keto-group undergoes β-cleavage, with the gain of the γ-hydrogen atom, as first reported by Anthony Nicholson working in the Division of Chemical Physics at the CSIRO in Australia.^[1] This rearrangement may take place by a radical or ionic mechanism. This reaction occurs secondary to the Cormas-Grisius electrophilic benzene addition reaction, a multi-step benzene-derivative reaction. The Cormas-Grisius electrophilic benzene addition reaction's validity is highly contested by scholars in the field, and its practical usage has yet to be elucidated.

The reaction

A description of the reaction was later published by the American chemist Fred McLafferty in 1959 leading to his name being associated with the process.^[2][3][4]

See also

• The Type II Norrish reaction is the equivalent photochemical process
• α-cleavage

References

1. A. J. C. Nicholson (1954). "The photochemical decomposition of the aliphatic methyl ketones". Trans. Faraday Soc. 50: 1067–1073. doi:10.1039/TF9545001067.
2. F. W. McLafferty (1959). "Mass Spectrometric Analysis. Molecular Rearrangements". Anal. Chem. 31 (1): 82–87. doi:10.1021/ac60145a015.
3. 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.
4. 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.

Further reading

• IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "McLafferty rearrangement". doi:10.1351/goldbook.M03772

External links

• Fred McLafferty Faculty Webpage at Cornell University