3.9.4

Elimination Reactions

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Elimination Reactions of Alcohols

So far we’ve seen how we can oxidise alcohols to get aldehydes, ketones and carboxylic acids. We can also get alkenes from alcohols.

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Dehydration

  • Dehydration reactions are just elimination reactions where water is eliminated.
    • The equation in the image shows how we can get an alkene from an alcohol via a dehydration reaction under acidic conditions.
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Mechanism of ethanol dehydration

  • Note the action of the acid catalyst.
  • Note how the positively charged alkane collapses to form the alkene in the final step.
Illustrative background for The action of the acid catalystIllustrative background for The action of the acid catalyst ?? "content

The action of the acid catalyst

  • The reaction needs an acid catalyst.
    • This catalyst protonates the -OH group to make it easier to eliminate the group.
    • The acid catalyst is reformed when the H+ is lost as the alkene forms in the last step.
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Why do this?

  • It turns out that we’re actually pretty good at producing alcohols without using crude oil.
  • This means we can get alkenes without cracking the alkanes from crude oil.
  • This means we can polymerise the alkenes and make polymers without using crude oil.

Jump to other topics

1Structure - Models of the Particulate of Matter

2Structure - Models of Bonding & Structure

3Structure - Classification of Matter

3.1The Periodic Table: Classification of Elements

3.2Periodic Trends

3.3Group 1 Alkali Metals

3.4Halogens

3.5Noble gases, group 18

3.6Functional Groups: Classification of Organic

3.7Functional Group Chemistry

3.8Alkanes

3.9Alcohols

3.10Halogenoalkanes

4Reactivity - What Drives Chemical Reaction?

5Reactivity - How Much, How Fast & How Far?

6Reactivity - The Mechanisms of Chemical Change

7Measurement, Data Processing & Analysis

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