CH3COCH3\mathrm{CH}_{3} \mathrm{COCH}_{3}CH3COCH3
HCOOH\mathrm{HCOOH}HCOOH
CH3COOH\mathrm{CH}_{3} \mathrm{COOH}CH3COOH
CH3OH\mathrm{CH}_{3} \mathrm{OH}CH3OH