H3CCOCl\mathrm{H}_{3} \mathrm{C} \mathrm{COCl}H3CCOCl
H2 N−CO−NH2\mathrm{H}_{2} \mathrm{~N}-\mathrm{CO}-\mathrm{NH}_{2}H2 N−CO−NH2
CH3CHO\mathrm{CH}_{3} \mathrm{CHO}CH3CHO
H2−CO−NH\mathrm{H}_{2}-\mathrm{CO}-\mathrm{NH}H2−CO−NH