Elimination — hydroxide ions

Year 1

AQA 3.3.3

Nucleophilic substitution & elimination · KOH in ethanol · hot, ethanolic

Reagents: KOH in ethanol · Conditions: hot, ethanolic

Step 1 of 1

1.OH⁻ acts as a BASE here: its lone pair attacks a hydrogen on the β-carbon (the carbon next to C–Br).
2.The C–H bonding pair moves in to become the new π bond between the two carbons.
3.Simultaneously the C–Br bond breaks heterolytically, releasing bromide.

Water, bromide and propene form in one concerted step — OH⁻ acted as a base, not a nucleophile.

Product: propene

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