Alkali-Catalyzed Equilibria of Unsaturated Compounds

When an afi or P,y unsaturatod carbonyl compound is heated with a strong base, an equilibrium is often established between the two isomers HO II O 

Similarly, allylbenzene is transformed almost irreversibly into propenyl-benzene  

8 For an excellent discussion of tautomorism in which this particular kind is included, see Baker, Taidomerism, Rout ledge and Sons, Ltd., London, England, 1934. 

These reactions appear to proceed through the formation of a common carbanion obtained by the attack of the base on a hydrogen atom attached to a carbon atom alpha to one of the unsaturated groups. For the a,0-/3,7 equilibria of unsaturatcd carbonyl compounds, the isomerization may be outlined as follows  

Exchange reactions with deuterium oxide solution support the idea of the formation of a common carbanion. Sodium vinyl acetate (XVI), for example, exchanges hydrogen for deuterium atoms in sodium hydroxide solution containing deuterium oxide.9 The rate is faster than the rate 

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