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Organic Chemistry

Reactions of alkenes

  • 3 things to know
  • Paper 2

Overview

The C=C functional group and why members of a homologous series react alike, complete and incomplete combustion of alkenes and their smoky flames, addition reactions with hydrogen, water and the halogens and their conditions, why alkanes cannot undergo addition, and naming and describing the displayed formulae of alkenes and their addition products.

What you need to know

Answer each one before you reveal it.

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Key term

What is the functional group of the alkenes?

Key term

What is a functional group?

Key term

Ethene decolourises bromine water. Predict how butene behaves with bromine water and justify your prediction.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the functional group of the alkenes?

    Model answer

    The carbon–carbon double bond, C=C.

  2. 2

    What is a functional group?

    Model answer

    A functional group is the group of atoms in a molecule that is responsible for the compound's characteristic reactions.

  3. 3

    In which part of an alkene molecule do its characteristic reactions take place?

    Model answer

    At the carbon–carbon double bond.

  4. 4

    Explain why all the members of a homologous series react in similar ways.

    Model answer

    They all contain the same functional group, and it is the functional group that determines how a compound reacts.

  5. 5

    Ethene decolourises bromine water. Predict how butene behaves with bromine water and justify your prediction.

    Model answer

    Butene also decolourises it, because both are alkenes with the same C=C functional group and so undergo the same reaction.

  6. 6

    Name the products of the complete combustion of an alkene.

    Model answer

    Carbon dioxide and water.

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