11.5.7

Properties of Alkenes - Addition Reactions

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Properties of Alkenes: Addition Reactions

Alkenes react in addition reactions with bromine, hydrogen, and steam, demonstrating specific properties and the reaction products.

Illustrative background for Introduction to alkenes and addition reactionsIllustrative background for Introduction to alkenes and addition reactions ?? "content

Introduction to alkenes and addition reactions

  • Alkenes are hydrocarbons with at least one carbon-carbon double bond.
  • Alkenes undergo addition reactions that break the double bond.
  • Addition reactions add atoms to the carbon atoms originally in the double bond.
    • These reactions help us study alkene properties and identify them.
  • In addition reactions, only one product is formed.
Illustrative background for Addition reaction with bromine or aqueous bromineIllustrative background for Addition reaction with bromine or aqueous bromine ?? "content

Addition reaction with bromine or aqueous bromine

  • When bromine (Br2) reacts with an alkene, the double bond breaks.
  • The bromine atoms add across the double bond.
  • This reaction changes the solution colour from orange-brown to colourless.
  • The product is a dibromo alkane.
    • Example: Ethene (C2H4) + Br2 → 1,2-dibromoethane (C2H4Br2).
Illustrative background for Addition of hydrogen with nickel catalystIllustrative background for Addition of hydrogen with nickel catalyst ?? "content

Addition of hydrogen with nickel catalyst

  • Alkenes react with hydrogen (H2) in the presence of a nickel (Ni) catalyst.
  • The double bond breaks, and hydrogen atoms add to the carbons.
  • This process is called hydrogenation, turning alkenes into alkanes.
    • Example: Ethene + H2 → Ethane (C2H6).
  • Catalysts speed up reactions without changing themselves.
Illustrative background for Addition of steam with acid catalystIllustrative background for Addition of steam with acid catalyst ?? "content

Addition of steam with acid catalyst

  • Steam (H2O) adds to alkenes in the presence of an acid catalyst like sulfuric acid (H2SO4).
  • The double bond breaks, forming an alcohol.
  • This process is called hydration.
    • Example: Ethene + steam → ethanol (C2H5OH).
  • Acid catalyst helps the reaction proceed faster.
Illustrative background for Structural and displayed formulae of productsIllustrative background for Structural and displayed formulae of products ?? "content

Structural and displayed formulae of products

  • For addition with bromine: from C=C to C-C with Br atoms attached.
  • For addition with hydrogen: from C=C to C-C with H atoms added.
  • For addition with steam: from C=C to C-C with OH and H atoms added.
    • Drawing structures helps visualise where new atoms join the chain.
    • Knowing these formulas shows how alkenes change during reactions.

Jump to other topics

1States of Matter

2Atoms, Elements & Compounds

3Stoichometry

4Electrochemistry

5Chemical Energetics

6Chemical Reactions

7Acids, Bases & Salts

8The Periodic Table

9Metals

10Chemistry of the Environment

11Organic Chemistry

11.1Formulae, Functional Groups & Terminology

11.2Naming Organic Compounds

11.3Fuels

11.4Alkanes

11.5Alkenes

11.6Alcohols

11.7Carboxylic Acids

11.8Polymers

12Experimental Techniques & Chemical Analysis

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