CH3COOH\mathrm{CH}_{3} \mathrm{COOH}CH3COOH
CH3CSNH2\mathrm{CH}_{3} \mathrm{CSNH}_{2}CH3CSNH2
CH3CONH2\mathrm{CH}_{3} \mathrm{CONH}_{2}CH3CONH2
CH3CH2NH2\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}CH3CH2NH2