Carbon tetroxide
Carbon tetroxide is a highly unstable oxide of carbon with formula . It was proposed as an intermediate in the O-atom exchange between carbon dioxide () and oxygen () at high temperatures. The C isomer, which is 138 kJ mol more stable than the D isomer, was first detected in electron-irradiated ices of carbon dioxide via infrared spectroscopy. The isovalent carbon tetrasulfide is also known from inert gas matrix. It has D symmetry with the same atomic arrangement as CO (D).