HCHO\mathrm{HCHO}HCHO
CH3CHO\mathrm{CH}_{3} \mathrm{CHO}CH3CHO
CH3CH2CHO\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}CH3CH2CHO
CH3CH2CH2CHO\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}CH3CH2CH2CHO