Alkenes: Properties and Structure

General Properties

• Alkenes are unsaturated hydrocarbons containing one or more carbon-carbon double bonds.
• General formula: CnH2n (where n is the number of carbon atoms).
• Also known as olefins.

Structure and Bonding

• Carbon atoms in alkenes are sp2 hybridized, resulting in a planar, trigonal geometry.
• The double bond consists of one σ (sigma) bond and one π (pi) bond.
• The π bond is responsible for the alkene's reactivity.

Physical Properties

• Alkenes are generally colorless, volatile liquids or gases.
• They have relatively low boiling points due to the weak intermolecular forces between molecules.
• Density is generally lower than that of water.

Chemical Properties

• Alkenes are more reactive than alkanes due to the presence of the double bond.
• They undergo addition reactions, such as:
  • Electrophilic addition (e.g., hydrogenation, halogenation, hydration).
  • Nucleophilic addition (e.g., reaction with organometallic compounds).
• Alkenes can also undergo polymerization reactions to form plastics.

Nomenclature

• Alkene names end in "-ene" and are based on the parent alkane name.
• The parent chain is the longest continuous chain containing the double bond.
• Numbering starts from the end of the chain closest to the double bond.

Examples

• Ethene (C2H4): the simplest alkene, also known as ethylene.
• Propene (C3H6): used in the production of polypropylene plastics.
• But-1-ene (C4H8): a common alkene used in the production of polybutadiene rubber.

General Properties of Alkenes

• Alkenes are unsaturated hydrocarbons with one or more carbon-carbon double bonds.
• General formula: CnH2n, where n is the number of carbon atoms.
• Also known as olefins.

Structure and Bonding

• Carbon atoms in alkenes are sp2 hybridized, resulting in a planar, trigonal geometry.
• The double bond consists of one σ (sigma) bond and one π (pi) bond.
• The π bond is responsible for the alkene's reactivity.

Physical Properties of Alkenes

• Alkenes are generally colorless, volatile liquids or gases.
• They have relatively low boiling points due to weak intermolecular forces between molecules.
• Density is generally lower than that of water.

Chemical Properties of Alkenes

• Alkenes are more reactive than alkanes due to the presence of the double bond.
• They undergo addition reactions, including:
  • Electrophilic addition (e.g., hydrogenation, halogenation, hydration).
  • Nucleophilic addition (e.g., reaction with organometallic compounds).
• Alkenes can also undergo polymerization reactions to form plastics.

Nomenclature of Alkenes

• Alkene names end in "-ene" and are based on the parent alkane name.
• The parent chain is the longest continuous chain containing the double bond.
• Numbering starts from the end of the chain closest to the double bond.

Examples of Alkenes

• Ethene (C2H4): the simplest alkene, also known as ethylene.
• Propene (C3H6): used in the production of polypropylene plastics.
• But-1-ene (C4H8): a common alkene used in the production of polybutadiene rubber.

Learn about the properties and structure of alkenes, including their general formula, bonding, and physical characteristics.