JAMB 2019 Chemistry · Question 1
A secondary alkanol can be oxidized to give an?
Options
- A.alkanone
- B.alkyne
- C.alkanoic acid
- D.alkanal
Answer: A. alkanone
Explanation written with AI and checked against the answer key
1. Analyze the question You're asked what product forms when a secondary alkanol (alcohol) is oxidized.
2. Explain the concept The product of oxidizing an alcohol depends on its class:
| Alcohol type | Structure | Oxidation product | |---|---|---| | Primary | R-CH₂OH | Alkanal (aldehyde), then alkanoic acid with further oxidation | | Secondary | R₂CH-OH | Alkanone (ketone) | | Tertiary | R₃C-OH | Not easily oxidized (no H on the carbon bearing the OH) |
Oxidation works by removing the hydrogen from the -OH group and the hydrogen on the carbon bearing the -OH. A secondary alcohol has exactly one hydrogen on that carbon, so once it is removed a C=O forms, and nothing more can be removed without breaking C-C bonds.
3. Step-by-step solution Take propan-2-ol, a typical secondary alkanol:
CH₃-CH(OH)-CH₃ --[K₂Cr₂O₇/H₂SO₄ or KMnO₄/H⁺]--> CH₃-CO-CH₃ + H₂O
- The product, propanone (acetone), is an alkanone.
- Alkynes (B) come from elimination or dehydrohalogenation, not oxidation.
- Alkanoic acids (C) come from oxidizing primary alcohols or aldehydes.
- Alkanals (D) come from the mild oxidation of primary alcohols.
4. Answer The correct option is A. alkanone.
5. Exam tip Remember: "1° → aldehyde → acid; 2° → ketone; 3° → no reaction." The number of hydrogens on the carbon carrying the -OH decides how far the oxidation can go.
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