CH3CH2COOH\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}CH3CH2COOH
ClCH2CH2COOH\mathrm{Cl} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH}ClCH2CH2COOH
Cl2CHCOOH\mathrm{Cl}_{2} \mathrm{CH} \mathrm{COOH}Cl2CHCOOH
CH3COOH\mathrm{CH}_{3} \mathrm{COOH}CH3COOH