H−COOH\mathrm{H}-\mathrm{COOH}H−COOH
H−CHO\mathrm{H}-\mathrm{CHO}H−CHO
CH3−CH2−OH\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{OH}CH3−CH2−OH
CH3−COOH\mathrm{CH}_{3}-\mathrm{COOH}CH3−COOH