Acetals specific/general acid catalysed hydrolysis

Intermolecular general acid catalysis of the hydrolysis of acetals and ketals Fig. 8 shows, in general terms, the reaction profile for the specific acid-catalysed hydrolysis of an acetal or a ketal. 

Scheme 3.1 (a) Specific acid-catalysed hydrolysis of j-carbo>yphenyl acetate where proton transfer occurs as a pre-equilibrium (b) General acid-catalysed hydration of styrene involving initial rate-limiting protonation... 

The stereochemical requirements for observation of intramolecular general acid catalysis seem quite severe - less effective participation is observed in the hydrolysis of 8-methoxymethoxy 1-naphthoic acid and none at all in the hydrolysis of (2-methoxymethoxyphenyl) acetic acid. Hydrolysis of 2-methoxymethoxy-3-methyl benzoic acid is quite strongly sterically accelerated [136] but this is also true of its specific acid-catalysed reactions. 

Bronsted and Grove (J. Amer. Chem. Soc. 1930, 52, 1394) showed that the hydrolysis of dimethyl acetal in water is specifically catalysed by hydrogen ions there is no "spontaneous reaction, nor does the reaction show general acid catalysis. Their measured values of the first-order rate constant k, determined by a dilatometric method in solutions of perchloric acid over a range of concentrations in water at 20 °C are given in table 1. 

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