3.10.2

Elimination Reactions

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Elimination Reactions

When a halogenoalkane is reacted with hydroxide ions, you can get an alcohol via substitution. But there is another reaction that can happen - elimination - which produces an alkene.

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Elimination mechanism

  • The image shows the mechanism for the elimination reaction of a halogenoalkane to form an alkene.
    • All the steps happen at the same time - it is a one step process.
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Elimination

  • Hydroxide ions are nucleophiles, but they are also bases.
  • They can take a proton off of a halogenoalkane if the next-door carbons have protons on them.
    • This results in formation of an alkene.
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Which reaction?

  • Hydroxide reacting with a halogenoalkane can either eliminate to produce an alkene or substitute to produce an alcohol.
    • Both are very possible.
  • To promote the elimination reaction, we can:
    • Use ethanol as the solvent rather than water.
    • Heat the reaction under reflux conditions.
      • Reflux involves using a reflux condenser to condense gases back into the reaction flask.

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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