Q90 · Practice questionComplex unfamiliar6 marks
QUESTION 90 (6 marks)
A pathway starts from 2-bromo-2-methylbutane. Heated ethanolic hydroxide gives predominantly 2-methylbut-2-ene. This alkene undergoes acid-catalysed hydration, giving the Markovnikov alcohol.
a) Classify the first reaction and write the alkene condensed structure. [2 marks]
b) Name and give the condensed structure of the alcohol. [2 marks]
c) Predict its response to heated acidified dichromate and justify. [2 marks]
WORKED SOLUTION
6 marksPractice marking scheme
Elimination; ; 2-methylbutan-2-ol, ; no ordinary oxidation because it is tertiary.
Elimination removes HBr. Hydration adds H to the less substituted double-bond carbon and OH to carbon 2. The OH-bearing carbon then has three carbon groups and no H, so it does not undergo the normal dichromate alcohol oxidation.
- Classifies elimination. [1 marks]
- Draws correct alkene. [1 marks]
- Names 2-methylbutan-2-ol. [1 marks]
- Draws correct alcohol structure. [1 marks]
- Predicts no dichromate oxidation under these conditions. [1 marks]
- Explains tertiary carbon lacks attached H. [1 marks]
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