CO2COOH
CO2COOH, also known as carbonyldioxycarboxylic acid, is a hypothetical molecule that combines structural features of carbon dioxide and carboxylic acid. Its chemical formula suggests a carbon atom doubly bonded to two oxygen atoms, with a third oxygen atom also bonded to the carbon and then to a hydrogen atom. This arrangement implies a central carbon atom with four bonds, two to oxygen atoms in a carbonyl-like fashion, and one to a hydroxyl group.
The existence of CO2COOH as a stable, isolable compound is not widely established in mainstream chemistry.