Edexcel IAL Chemistry 15.4 Racemic mixture
Look for a 50:50 mixture of enantiomers or equal attack on both faces of a planar carbonyl, then link the sample to no net optical activity.
- Syllabus
- First assessment 2019
- Course
- Chemistry YCH11
- Level
- A2
Exam points
- State that a racemic mixture contains equal amounts of the two enantiomers.
- Explain no optical activity by equal and opposite rotations cancelling in the sample.
- Recognise enantiomer pairs that can form a racemic mixture when combined.
15.4—What is meant by the term ‘racemic mixture’ question 1
[Maximum number: 1]
This question is about carboxylic acids and their derivatives.
Lactic acid, CH3CH(OH)COOH, is produced in muscles as a result of anaerobic respiration.
A laboratory sample of lactic acid does not rotate the plane of plane-polarised monochromatic light.
Give a reason for this observation.
An answer that makes reference to the following point:
- it is a racemic mixture or contains equal amounts of the two enantiomers / (optical) isomers
Allow rotations caused by both enantiomers / isomers cancel
Ignore just contains two enantiomers / isomers
Do not award plane-polarised light cannot pass through the solution
(1)
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