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Derivatives of Carboxylic Acids

The laboratory preparation of a liquid ester

  • 3 things to know
  • Unit A2 1

Overview

Why anti-bumping granules are placed in the flask, why the mixture is heated under reflux and how the two layers are separated after washing.

What you need to know

Answer each one before you reveal it.

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Key term

State the three substances mixed in the flask at the start of a laboratory ester preparation.

Key term

Explain why the concentrated sulfuric acid is added slowly with swirling and cooling in a laboratory ester preparation

Key term

Describe how the crude ester is removed from the reaction mixture after reflux.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the three substances mixed in the flask at the start of a laboratory ester preparation.

    Model answer

    The carboxylic acid, the alcohol and a few drops of concentrated sulfuric acid are mixed together.

  2. 2

    Explain why the concentrated sulfuric acid is added slowly with swirling and cooling.

    Model answer

    Mixing concentrated sulfuric acid with organic liquids is strongly exothermic, so adding it slowly prevents the mixture from boiling over.

  3. 3

    State why anti-bumping granules are placed in the flask.

    Model answer

    They provide nucleation sites so the liquid boils smoothly rather than surging.

  4. 4

    Explain why the mixture is heated under reflux.

    Model answer

    Reflux allows the mixture to be kept at its boiling point for a long time without any of the volatile reactants or products escaping.

  5. 5

    Describe how the crude ester is removed from the reaction mixture after reflux.

    Model answer

    The apparatus is rearranged for distillation and the ester is distilled off, being collected over a narrow range around its boiling point.

  6. 6

    Name the reagent used to wash the crude distillate and state what it removes.

    Model answer

    Sodium carbonate solution is used, and it neutralises and removes the unreacted carboxylic acid and any sulfuric acid carried over.

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