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Stereoisomerism

Chiral centres and enantiomers

  • 3 things to know
  • Component 2

Overview

Recall questions on what makes a carbon atom a chiral centre, the definition of an enantiomer and what non-superimposable means, identifying the chiral centre in named molecules, why some molecules have none, and how the chemical and physical properties of two enantiomers compare.

What you need to know

Answer each one before you reveal it.

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Key term

Define a chiral centre.

Key term

What other name is given to a chiral centre?

Key term

Define an enantiomer.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define a chiral centre.

    Model answer

    A chiral centre is a carbon atom carrying four different atoms or groups.

  2. 2

    What other name is given to a chiral centre?

    Model answer

    An asymmetric carbon atom.

  3. 3

    Define an enantiomer.

    Model answer

    An enantiomer is one of a pair of stereoisomers that are non-superimposable mirror images of each other.

  4. 4

    What does non-superimposable mean here?

    Model answer

    However the two molecules are turned in space, one cannot be placed exactly on top of the other so that every atom coincides.

  5. 5

    Give an everyday analogy for a pair of enantiomers.

    Model answer

    A left hand and a right hand, which are mirror images and cannot be superimposed however they are turned.

  6. 6

    How many optical isomers does a molecule with one chiral centre have?

    Model answer

    Two.

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