CH3CHO\mathrm{CH}_{3} \mathrm{CHO}CH3CHO
CH3CH2COCH2CH3\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COCH}_{2} \mathrm{CH}_{3}CH3CH2COCH2CH3
CH3CO2CH3\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3}CH3CO2CH3
HCHO\mathrm{HCHO}HCHO