Aldol 反应
第一步:
CH3COCH3 + OH- = CH3COCH2-
CH3COCH2- + O=C(CH3)2 = CH3COCH2-C(OH)(CH3)2
脱去一分子水：
CH3COCH2-C(OH)(CH3)2 = CH3COCH=C(CH3)2