Hydrolysis
Hydroxide attacks the saturated carbon bearing bromine while the C-Br bond breaks. This primary-substrate SN2 route replaces bromide with OH and preserves both carbon atoms; aqueous conditions favour this branch over elimination.
- Reagents
- Aqueous NaOH or KOH
- Conditions
- Warm aqueous alkali
- Reaction class
- Hydrolysis
- Equation
- CH3CH2Br + OH- -> CH3CH2OH + Br-
Overview
Hydroxide attacks the saturated carbon bearing bromine while the C-Br bond breaks. This primary-substrate SN2 route replaces bromide with OH and preserves both carbon atoms; aqueous conditions favour this branch over elimination.
Transformation
- Equation
- CH3CH2Br + OH- -> CH3CH2OH + Br-
- Reagents
- Aqueous NaOH or KOH
- Environment
- Warm aqueous alkali
- Reaction class
- Hydrolysis
- Mechanism
- SN2 nucleophilic substitution
- Evidence level
- source-backed molecular example
Scope and limitations
- Scope
- Primary haloalkane undergoing nucleophilic substitution.
- Limitations
- Ethanolic base and stronger heating increase the competing elimination route.
Related reactions
- Iodoform reaction: Ethanol → Triiodomethane products
Ethanol is oxidised and cleaved by alkaline iodine to give triiodomethane and methanoate.
- Partial oxidation: Ethanol → Ethanal
Ethanol is oxidised to ethanal.
- Oxidation: Ethanol → Ethanoic acid
Ethanol is oxidised to ethanoic acid.
- Reduction: Ethanal → Ethanol
Ethanal is reduced to ethanol.
- Esterification: Ethanol → Ethyl acetate
Ethanoic acid and ethanol combine reversibly to form ethyl acetate and water.
- Acid hydrolysis: Ethyl acetate → Ethanol
Ethyl acetate and water react reversibly to form ethanoic acid and ethanol.
- Hydration: Ethene → Ethanol
Ethene gives ethanol through hydration.
- Dehydration: Ethanol → Ethene
Ethanol gives ethene through dehydration.
- Intermolecular dehydration: Ethanol → Diethyl ether
Protonation turns one ethanol OH group into a better leaving group. The oxygen of another ethanol molecule displaces water, and deprotonation gives diethyl ether; stronger dehydration conditions instead favour ethene.
- Elimination: Bromoethane → Ethene
The base removes a hydrogen from the carbon next to bromine. The C-H electrons form the C=C pi bond as bromide departs, so elimination removes H and Br without changing the two-carbon skeleton.
- Cyanide substitution: Bromoethane → Propanenitrile
The carbon end of cyanide attacks the primary carbon of bromoethane as bromide leaves. The new C-C bond joins cyanide’s carbon to the original chain, giving a three-carbon nitrile rather than acetonitrile.
- Ammonia substitution: Bromoethane → Ethylamine
Ammonia attacks the carbon bearing bromine to give an alkylammonium intermediate. A further ammonia molecule removes a proton to release ethylamine; the product can undergo additional alkylation if haloalkane remains.
- Acid hydrolysis: Ethyl butyrate → Ethanol
Water attack and proton transfers permit the ethoxy fragment to leave as ethanol. Re-forming the carbonyl produces butanoic acid on the other branch.
References
- Pearson Edexcel International Advanced Level Chemistry Scheme of WorkPearson Education Limited · Pearson qualifications · 2018
Official Pearson teaching guidance specifying chloroalkane-relevant conditions: aqueous alkali, ethanolic potassium hydroxide, alcoholic ammonia, alcoholic potassium cyanide, and PCl5 alcohol chlorination.