Enes

Enes are a class of hydrocarbons defined by the presence of at least one carbon–carbon double bond. They are unsaturated and are commonly referred to in chemistry as alkenes, with the name derived from the -ene suffix used in systematic nomenclature. Enes occur in linear, branched, and cyclic forms, including cycloalkenes.

General characteristics include a formula of CnH2n for acyclic enes with one double bond; cyclic enes typically have the formula CnH2n−2. The double bond restricts rotation, leading to stereoisomerism when each carbon of the double bond bears different substituents. When more than one double bond is present, the compounds are called dienes, trienes, and so on, with the position of double bonds indicated in the name.

Nomenclature and examples: The simplest enes are ethene (ethylene), propene (propylene), and butenes. The location of the double bond is specified in the name, such as but-1-ene or but-2-ene. Cycloalkenes are named as cycloalkenes, e.g., cyclohexene.

Reactivity and applications: The C=C double bond is a reactive site that undergoes electrophilic addition reactions, including hydrogenation, halogenation, hydrohalogenation, and hydration. Enes readily polymerize under suitable catalysts, with ethene giving polyethylene, a foundational plastic. Beyond polymers, enes serve as feedstocks for solvents, dyes, and numerous intermediate chemicals.

Production and safety: Industrially, enes are produced mainly by cracking and other refining processes in the petrochemical industry. They are typically flammable and can form explosive mixtures with air, so proper handling, storage, and ventilation are essential.