The aldol addition reaction is reversible. When the β-hydroxy ketone shown below is exposed to aqueous NaOH, a retro-aldol reaction occurs which yields acetophenone and formaldehyde as the products:
Propose a curved-arrow mechanism for this reaction. Use curved arrows to show movement of electron pairs, and draw structures for all important reaction intermediates. If an intermediate is a resonance hybrid, it is only necessary to draw the MOST IMPORTANT contributing resonance structure. Be sure to show all lone pairs and nonzero formal charges.