羧酸:C-C-C-COOHC-C(-C)-COOH酮:C-C(=O)-C(-OH)-CC-C(=O)-C-C-OHC(-OH)-C(=O)-C-C醛:C(-OH)-C-C-CHOC-C(-OH)-C-CHOC-C-C(-OH)-CHOC(-OH)-C(-C)-CHOC-C(-C)(-OH)-CHO(表示侧链)