Make an alcohol by hydroxide substitution
Hydrolyse a halogenoalkane with aqueous NaOH and heat to replace X with OH.
Section 16 · Hydroxy compounds
AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. State reagents and conditions, follow the stated reaction pathway, and distinguish each alcohol class and oxidation product. Written practice is self-checked
Before you begin
- Use functional-group formulae and reaction types from Topic 13, alkene reactions from Topic 14, and halogenoalkane substitution from Topic 15.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which medium is used to substitute a halogen with OH to make an alcohol?
What you will learn
- Select aqueous NaOH and heat
- Replace C–X with C–OH
- Predict alcohol class from structure
Hydroxide replaces the halogen
A halogenoalkane reacts with aqueous NaOH and heat to form an alcohol by nucleophilic substitution. OH⁻ attacks the carbon bonded to X as the C–X bond pair moves to X.
For bromoethane: C₂H₅Br + NaOH(aq) → C₂H₅OH + NaBr. The carbon skeleton is unchanged; only X is replaced by OH.
Aqueous conditions matter
Aqueous hydroxide favors substitution to an alcohol. Ethanolic NaOH with heat is used to eliminate HX and form an alkene, as taught in Topic 15.
Name the medium, heat and target group. If the halogenoalkane structure is branched, trace the carbon bearing X to classify the alcohol product.
Pause and explain
What happens to the carbon skeleton during hydroxide substitution?
Worked example
Convert 2-bromobutane into an alcohol using the syllabus route.
Show the worked solution
- Replace Br on carbon 2 with OH.
- Keep the four-carbon skeleton unchanged.
- State aqueous NaOH and heat.
Answer CH₃CHBrCH₂CH₃ + NaOH(aq) → CH₃CH(OH)CH₂CH₃ + NaBr; heat.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write the equation and conditions for converting 1-chloropropane into propan-1-ol.
Give me a hint
Replace Cl with OH and include the sodium salt.
Compare my reasoning
- Use aqueous NaOH and heat.
- Keep three carbon atoms in the alcohol.
- Add NaCl as the inorganic coproduct.
CH₃CH₂CH₂Cl + NaOH(aq) → CH₃CH₂CH₂OH + NaCl; heat.
Look for these in your work
- Product structure correct
- Coproduct included
- Conditions stated
A learner predicts but-1-ene from 1-bromobutane and aqueous NaOH. Correct the route.
Give me a hint
Use the solvent to choose substitution or elimination.
Compare my reasoning
- Aqueous hydroxide favors substitution.
- OH replaces Br to form butan-1-ol.
- Ethanolic hydroxide and heat would favor elimination.
Aqueous NaOH gives butan-1-ol by substitution; ethanolic NaOH/heat is the alkene route.
Look for these in your work
- Solvent interpreted
- Alcohol named
- Alternative distinguished
What alcohol class forms when 2-chloropropane is treated with aqueous NaOH and heat?
Give me a hint
Identify the carbon attached to the incoming OH.
Compare my reasoning
- OH replaces Cl at carbon 2.
- That carbon is bonded to two other carbons.
- An OH-bearing carbon with two carbon neighbours is secondary.
Propan-2-ol, a secondary alcohol.
Look for these in your work
- Position preserved
- Neighbour count correct
- Class named
Common mistakes
- Using ethanolic NaOH when the target is an alcohol
- Adding OH without removing X
- Changing the carbon skeleton
What can you explain now?
Which medium is used to substitute a halogen with OH to make an alcohol?
Compare with the explanation
Aqueous NaOH
Aqueous hydroxide and heat give the alcohol route.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
What structural change and conditions convert a halogenoalkane into an alcohol?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.