Mass spectrometry McLafferty rearrangement

Djerassi, C. Tokes, L. Mass Spectrometry in Stractural and Stereochemical Problems. XCIII. Further Observations on the Importance of Interatomic Distance in the McLafferty Rearrangement. Synthesis and Fragmentation Behavior of Deuterium-Labeled 12-Oxo Steroids. J. Am. Chem. Soc. 1966,88,536-544. 

Henion, J.D. Kingston, D.G.I. Mass Spectrometry of Organic Compounds. IX. McLafferty Rearrangements in Some Bi-cyclic Ketones. J. Am. Chem. Soc. 1974, 96.2532-2536. 

The rearrangement-elimination reaction (120) is one example of the so-called McLalferty rearrangement (McLafferty, 1959) commonly encountered in mass spectrometry. The first step in McLafferty s scheme (120) is regarded as a bond-forming reaction of the radical site... 

Methyl n-propyl ketone and methyl n-butyl ketone have been subjected to 3 Mev y-rays (Pitts and Osborne, 1961). Two of the many products, acetone and an olefin (ethylene from the first ketone and propylene from the second), could have been formed by an intramolecular hydrogen rearrangement analogous to the McLafferty rearrangement in mass spectrometry and the Norrish type II photochemical process (Section D). Essentially the same interpretation has been mentioned briefly by Ausloos and Paulson (1958). 

Review of literature Heinrich, P., Methoden der Organischen Chemie, Houben-Weyl-Muller, vol. IV/Sb. p. 891 ff., Thieme Verlag, Stuttgart, 1975 McLafferty-rearrangement of ketones and numerous further classes of compounds see e.g. Rose, M. E., Johnstone, R. A. W. Mass spectrometry for chemists and biochemists, Cambridge University Press, Cambridge, p. 222 ff. (1982)... 

McLafferty rearrangement Decomposition in mass spectrometry of carbonyl compounds having a y-hydrogen. giving an alkene and an enol. 

McLafferty rearrangement In mass spectrometry, the loss of an alkene fragment by a cyclic rearrangement of a carbonyl compound having y hydrogens, (p. 814) nitrile A compound containing the cyano group, C = N. (p. 824)... 

Electron impact mass spectrometry of carboxylic acids usually produces only a weak molecular ion (M ). If the carboxylic add has a total molecular weight below about 150, an M -17 fragment (due to the loss of the hydroxyl), as well as an M+-45 (as a consequence of losing CO2H), is frequently observed. With the larger carboxylic acids, a McLafferty rearrangement such as the one shown in Scheme 5.5 (which should be compared with Scheme 5.3) intrudes. 

The McLafferty rearrangement, discovered in 1952, is the only named reaction in mass spectrometry. 

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