CH2O\mathrm{CH}_{2} \mathrm{O}CH2O
CHO\mathrm{CHO} \text {}CHO
C2H4O\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}C2H4O
C3H8O2\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{2}C3H8O2
C4H3O\mathrm{C}_{4} \mathrm{H}_{3} \mathrm{O}C4H3O