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Carbonyls, Carboxylic Acids and Derivatives

Oxidation of Aldehydes and Distinguishing Tests

  • 3 things to know
  • Papers 2 and 3

Overview

Why aldehydes oxidise and ketones do not, and the tests that show it.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Process

How is an aldehyde distinguished from a ketone?

Key term

What is the positive result when Fehling's solution reacts with an aldehyde?

Key term

What is the positive result when Tollens' reagent reacts with an aldehyde?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What type of oxidation product do aldehydes readily form?

    Model answer

    Carboxylic acids

  2. 2

    What reagent can be used to distinguish between aldehydes and ketones based on the formation of a brick-red precipitate?

    Model answer

    Fehling's solution

  3. 3

    What reagent can be used to distinguish between aldehydes and ketones based on the formation of a silver mirror?

    Model answer

    Tollens' reagent

  4. 4

    What is the positive result when Fehling's solution reacts with an aldehyde?

    Model answer

    A brick-red precipitate forms

  5. 5

    What is the positive result when Tollens' reagent reacts with an aldehyde?

    Model answer

    A silver mirror forms on the inside of the test tube

  6. 6

    Why do aldehydes give a positive result with Fehling's solution and Tollens' reagent while ketones do not?

    Model answer

    Aldehydes can be readily oxidised to carboxylic acids, whereas ketones cannot be easily oxidised

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AOxidation is the loss of electrons.
BReduction is the gain of electrons.
CAn oxidising agent is an electron acceptor.

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