HCHO \text { HCHO } HCHO
CH3CHO\mathrm{CH}_{3} \mathrm{CHO}CH3CHO
C6H5−CHO\mathrm{C}_{6} \mathrm{H}_{5}-\mathrm{CHO}C6H5−CHO
(CH3)3CCHO\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO}(CH3)3CCHO