C2H4O2\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}C2H4O2
CO,O2\mathrm{CO}, \mathrm{O}_{2}CO,O2
N2,O2\mathrm{N}_{2}, \mathrm{O}_{2}N2,O2
N2′CO\mathrm N_{2^{\prime}} \mathrm{CO}N2′CO