Non-conjugated β, γ-unsaturated ketones, such as 3-cyclohexenone, as in base-catalyzed equilibrium with their α,β-unsaturated isomers. An interesting consequence of this isomerization of unsaturated ketones is that 2-substituted cyclopentenones, such as 2-methyl-2-cyclopentenone, can be interconverted with 5-substituted 2-cyclopentenones. The first intermediate in this reaction has three resonance structures.
Draw all resonance structures for the first intermediate in the conversion of 2-methyl-2-cyclopentenone to 5-methyl-2-cyclopentenone.