Stability of Acetals and Ketals

As was observed in 1888 by Meunier,24 during a study of the properties of tribenzylidene-D-mannitol, acetals and ketals are readily hydrolyzed by aqueous acids, but are usually stable under alkaline conditions. In this 

Notable progress in the structural analysis of methylene derivatives of the polyhydric alcohols resulted from the investigations of Hann, Hudson and their co-workers26 80,40-4 into the behavior of these compounds during acetolysis. It was found that a mixture of acetic anhydride, acetic acid and 1-2% sulfuric acid ruptures preferentially any methylene bridge which spans a primary and a secondary position, giving the acetate ester of the primary hydroxyl and the acetoxymethyl ether of the secondary hydroxyl subsequent treatment with sodium methoxide removes each of these substituents. Under similar conditions, the acetolysis of a benzylidene compound results in the replacement of the arylidene residue, wherever it is located in the molecule, by two acetyl groups.16 29 47 48 

The influence of ring size and position upon the stabilities of acetals and ketals during hydrolysis and acetolysis will be considered more fully in a later section (page 185). 

The Oxidation of Acetals and Ketals of the Tetritols with Glycol-splitting Reagents 

Positions engaged in cyclization Oxidant consumed (moles) Formaldehyde produced (moles) Formic acid produced (moles) 

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