monoalkene

A monoalkene is a type of hydrocarbon that contains exactly one carbon–carbon double bond. It is a member of the alkenes, also called monounsaturated hydrocarbons, and is distinct from polyenes, which have two or more C=C bonds. Monoalkenes can be acyclic, with a single C=C along a carbon chain, or monocyclic, containing one double bond within a ring.

Structural types and examples: common acyclic monoalkenes include ethene (ethylene), propene, and butenes. Cyclic examples include cyclohexene and cyclopentene. In acyclic examples the double bond has a defined position in the carbon skeleton; in cycloalkenes the double bond lies within the ring.

Nomenclature: IUPAC naming assigns a base name from the longest carbon chain or ring, with the double bond indicated by the suffix -ene and a locant to specify its position. For cycloalkenes, the ring is named as cycloalkene, with locants for substituents as needed.

Reactivity and properties: the carbon–carbon double bond is the principal reactive site, undergoing additions such as hydrogenation, halogenation, hydrohalogenation, and hydration. Physical properties vary with chain length and substituents, but alkenes are generally less saturated than alkanes and display characteristic unsaturation-driven chemistry.

Occurrence and production: monoalkenes are abundant in petroleum and are produced by processes such as catalytic cracking and dehydrogenation of alkanes, as well as dehydration of alcohols for smaller members. Ethene, propene, and isobutene are among the most important industrial monoalkenes.

Applications: they serve as key monomers for polymers (for example, polyethylene from ethene and polypropylene from propene) and as versatile intermediates in organic synthesis and manufacturing. Safety considerations include flammability and reactivity of the double bond.