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Alcohols and Carboxylic Acids

Dehydration of alcohols to alkenes

  • 3 things to know
  • Components 1 and 2

Overview

Dehydration of an alcohol, alternative method of dehydrating ethanol that uses a solid and why the dehydration of bioethanol is of growing industrial interest.

What you need to know

Answer each one before you reveal it.

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Key term

What is meant by the dehydration of an alcohol?

Key term

Write the equation for the dehydration of ethanol.

Key term

State the reagent and conditions for the dehydration of ethanol using an acid.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is meant by the dehydration of an alcohol?

    Model answer

    Dehydration is the removal of a molecule of water from the alcohol, which leaves a carbon-carbon double bond.

  2. 2

    Name the type of reaction that the dehydration of an alcohol represents.

    Model answer

    It is an elimination reaction.

  3. 3

    Write the equation for the dehydration of ethanol.

    Model answer

    C₂H₅OH → C₂H₄ + H₂O.

  4. 4

    State the reagent and conditions for the dehydration of ethanol using an acid.

    Model answer

    Ethanol is heated with an excess of concentrated sulfuric acid at about 170 °C.

  5. 5

    Name an alternative acid catalyst to concentrated sulfuric acid for the dehydration of an alcohol.

    Model answer

    Concentrated phosphoric acid can be used instead.

  6. 6

    Describe the alternative method of dehydrating ethanol that uses a solid.

    Model answer

    The ethanol vapour is passed over heated aluminium oxide at about 300 °C, and the alkene is collected over water.

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