Ketenes are a class of organic compounds characterized by a cumulated double bond system, specifically the structure R2C=C=O, where R represents hydrocarbon groups. They are highly reactive intermediates in organic chemistry, often used in the synthesis of various functional groups, including carboxylic acids, amides, and lactams. Due to their reactivity, ketenes can participate in several important reactions, such as cycloadditions and nucleophilic additions. Their unique structure allows them to act as both electrophiles and nucleophiles, making them versatile building blocks in the development of complex organic molecules.