Definitions [1]
Definition: Alkenes
Alkenes are compounds with at least one carbon-carbon double bond. Alkenes form a homologous series having the general formula Cn H2n
Key Points
Key Points: Ethene
- Ethene (C₂H₄) is the first member of the alkene series, found in natural gas and acts as a plant hormone responsible for fruit ripening.
- Each carbon in ethene forms two C–H single bonds and one C=C double bond, making a planar (flat) molecule.
- The bond angles in ethene (H–C–H and H–C=C) are approximately 120°, showing trigonal planar geometry.
- Structure of Ethene:
Key Points: Physical Properties of Alkenes
- Ethene is a colourless, flammable gas with a faint, sweet smell.
- It has a melting point of –169°C and boiling point of –102°C.
- Slightly soluble in water but highly soluble in organic solvents; has a mild anaesthetic effect.
Key Points: Chemical Properties of Alkenes
- Ethene reacts with hydrogen, halogens, and acids to form saturated compounds like ethane and alcohols.
- It forms polythene through polymerisation.
- Burns with a sooty flame and gives ethylene glycol with KMnO₄.
Key Points: Uses of Ethene
- Used to make polythene and synthetic chemicals.
- Converted to ethanol for cosmetics and toiletries.
- Helps in fruit ripening.
- Used in epoxyethane and oxy-ethylene flame for detergents and metal cutting.
