Aromatics rearrangements

H. J. Shine, Aromatic Rearrangements Elsevier Science Publishing Co., New York, 1967, Chapt. 2. 

In this, as in many catalysed reactions, the protonated substrate is postulated as an intermediate, and although the proposed reaction scheme in fact accords with all the known experimental facts it perhaps would be instructive to determine the dependence of the rate coefficient on the Hammett acidity function at high acid concentration and also to investigate the solvent isotope effect kD2JkH20. Both these criteria have been used successfully (see Sections 2.2-2.4) to confirm the intermediacy of the protonated substrate in other acid-catalysed aromatic rearrangements. 

Shine, H. J. (1967). Aromatic Rearrangements , Elsevier, Amsterdam, London and New York, p. 284. 

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