HCOOH\mathrm{HCOOH}HCOOH
CH3COOH\mathrm{CH}_{3} \mathrm{COOH}CH3COOH
CH3CH2COOH\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}CH3CH2COOH
CH3COOC2H5\mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5}CH3COOC2H5
None