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Hydrocarbons

Alkenes: Structure, Bonding and Electrophilic Addition

  • 3 things to know
  • Papers 2 and 3

Overview

The C=C double bond as a centre of high electron density, and the mechanism of electrophilic addition.

What you need to know

Answer each one before you reveal it.

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Key term

Name the three reagents that add across the C=C double bond of an alkene by electrophilic addition.

Key term

What does the term "unsaturated" mean when describing alkenes?

Key term

What type of covalent bond is present in alkenes?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What type of hydrocarbons are alkenes classified as?

    Model answer

    Unsaturated hydrocarbons

  2. 2

    What does the term "unsaturated" mean when describing alkenes?

    Model answer

    The molecule contains at least one carbon-carbon double bond, meaning not all carbon atoms are bonded to the maximum number of hydrogen atoms

  3. 3

    What type of covalent bond is present in alkenes?

    Model answer

    A double covalent bond between two carbon atoms

  4. 4

    Why is the carbon-carbon double bond in alkenes described as a centre of high electron density?

    Model answer

    The double bond contains four shared electrons (two bonding pairs), creating a region of high electron density above and below the plane of the bond

  5. 5

    What type of reagents are attracted to the carbon-carbon double bond in alkenes?

    Model answer

    Electrophiles

  6. 6

    Why does the electron-rich carbon-carbon double bond leave alkenes open to electrophilic attack?

    Model answer

    Electrophiles are electron-pair acceptors that are attracted to regions of high electron density; the electron-rich double bond provides electrons for electrophiles to attack

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