McLafferty reaction

Zollinger, M. Seihl, J. McLafferty Reactions in Even-Electron Ions Org. Mass Spectrom. 1985, 77,649-661. 

A concrete example for the competition between the rearrangement reaction and the simple benzyUc cleavage is shown in Scheme 8. In the El mass spectrum of 3-(n-butyl)phenol m-23, the McLafferty reaction of gives rise to the base peak at... 

The McLafferty reaction in alkylphenols occurs stepwise The migration of a y -H to one of the ortho positions generates distonic ions 24 en route to the fragmentation products (Scheme 8). It has been shown that the relative stability of these reactive intermediates governs the competition between the McLafferty reaction and the benzylic cleavage in the El source and that its influence is more important than the relative stability of the... 

The close relations between odd- and even-electron cations is shown in Scheme 9. Viewed in a retrosynthetic manner, the protonated cresols [7 + H]+, representing parent species for the ionic part of the distonic ions 24, can be generated by addition of an H atom to the radical cations 7 + as well as by addition of a proton to the neutral arenes 7. In the same way, the radical cations 22a, representing the ionic fragments of the McLafferty reaction, can be formed both by addition of H to the benzylic cations 9 and by addition of H+ to the benzylic radicals 25. 

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