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Electrophilic addition — HBr
Year 1
AQA 3.3.4
Electrophilic addition · HBr · room temperature
Watch every step, with the electron flow and reasoning shown.
Reagents: HBr · Conditions: room temperature
Step 1 of 2
- 1.The electron-rich π bond attacks the δ+ hydrogen of H–Br — the alkene is the nucleophile here, H is the electrophile.
- 2.The H–Br bond breaks heterolytically; both electrons go to the more electronegative bromine.
A carbocation forms as H adds to one carbon; Br⁻ is released.
Step 2 of 2
- 1.A lone pair on the bromide ion forms a bond to the positively charged carbon.
Br⁻ bonds to the carbocation: bromoethane.
Product: bromoethane
Watched it? Now draw it yourself — that's what the exam asks.
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