Reaction XII.—Reduction of Aldehydes and Ketones to Pinacones

This side reaction cannot be avoided when reducing aliphatic ketones, but in the aromatic series either product can be obtained by varying the conditions of the reduction. An alkaline reduction favours alcohol production pinacones are formed when acid reducing agents are employed (see Preparation 16). 

Pinacones can also be obtained by using suitable electrolytic reductions. Aldehydes, too, have been brought within the scope of the reaction. Thus hydrobenzoin [s-diphenyl-ethan-diol] has been prepared from benzalde-hyde by an acid reduction. 

Acetone, the simplest ketone, gives the simplest pinacone. 

The pinacones formed from acetophenone, benzophenone, and many 

For photochemical reduction of benzophenone to benzpinacone by means of isopropyl alcohol, see O.S., XIV., 8. 

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