Here below some basic MCQ’s about “Aldehydes, Ketones and Carboxylic Acids Preperation and Properties” with answer which is explained in details for exam practice. Let’s check one by one.
1. Which of the following compounds can be prepared by the oxidation of primary alcohols?
a) Ketones
b) Aldehydes
c) Carboxylic acids
d) Esters
Answer: b) Aldehydes
Explanation: Primary alcohols are oxidized to aldehydes under controlled conditions (with reagents like PCC, CrO₃, etc.). Further oxidation of aldehydes leads to carboxylic acids.
2. The reagent used for the oxidation of secondary alcohols to ketones is:
a) Tollen’s reagent
b) PCC (Pyridinium chlorochromate)
c) Fehling’s solution
d) Grignard reagent
Answer: b) PCC (Pyridinium chlorochromate)
Explanation: Secondary alcohols are oxidized to ketones using oxidizing agents such as PCC, which selectively oxidizes secondary alcohols without over-oxidizing.
3. Which of the following methods is used to prepare aldehydes from alkenes?
a) Ozonolysis
b) Hydroboration-oxidation
c) Friedel-Crafts acylation
d) Wurtz reaction
Answer: a) Ozonolysis
Explanation: Ozonolysis of alkenes involves cleavage of the double bond, producing aldehydes or ketones depending on the structure of the alkene.
4. Which of the following reagents is used to reduce carboxylic acids to primary alcohols?
a) LiAlH₄ (Lithium aluminium hydride)
b) KMnO₄ (Potassium permanganate)
c) H₂/Pd
d) PCC (Pyridinium chlorochromate)
Answer: a) LiAlH₄
Explanation: Lithium aluminium hydride (LiAlH₄) is a strong reducing agent that reduces carboxylic acids to primary alcohols. It does not stop at the aldehyde stage.
5. Which of the following is the correct order of reactivity towards nucleophilic addition reactions?
a) Ketones > Aldehydes > Carboxylic acids
b) Carboxylic acids > Ketones > Aldehydes
c) Aldehydes > Ketones > Carboxylic acids
d) Ketones > Carboxylic acids > Aldehydes
Answer: c) Aldehydes > Ketones > Carboxylic acids
Explanation: Aldehydes are more reactive than ketones because of less steric hindrance and greater electrophilicity. Carboxylic acids are the least reactive due to resonance stabilization and the presence of the electron-withdrawing -OH group.
6. Which of the following reagents will convert an aldehyde into a carboxylic acid?
a) PCC
b) Fehling’s solution
c) KMnO₄
d) NaBH₄
Answer: c) KMnO₄
Explanation: Potassium permanganate (KMnO₄) is a strong oxidizing agent that oxidizes aldehydes to carboxylic acids.
7. Which of the following reagents is used for the reduction of aldehydes to primary alcohols?
a) LiAlH₄
b) NaBH₄
c) H₂/Pt
d) All of the above
Answer: d) All of the above
Explanation: LiAlH₄, NaBH₄, and catalytic hydrogenation (H₂/Pt) all reduce aldehydes to primary alcohols. NaBH₄ is milder compared to LiAlH₄.
8. Which of the following compounds does not give a positive Tollen’s test?
a) Formaldehyde
b) Benzaldehyde
c) Acetone
d) Acetaldehyde
Answer: c) Acetone
Explanation: Tollen’s reagent is used to test for aldehydes. Since acetone is a ketone, it does not give a positive Tollen’s test.
9. The IUPAC name of CH₃-CO-CH₃ is:
a) Propanal
b) Propanone
c) Acetone
d) Acetic acid
Answer: b) Propanone
Explanation: The IUPAC name of the simplest ketone (CH₃-CO-CH₃) is propanone. It is commonly known as acetone.
10. Which of the following methods can be used to prepare ketones?
a) Oxidation of secondary alcohols
b) Ozonolysis of alkenes
c) Friedel-Crafts acylation
d) All of the above
Answer: d) All of the above
Explanation: Ketones can be prepared by the oxidation of secondary alcohols, the ozonolysis of alkenes, and the Friedel-Crafts acylation of aromatic compounds with acid chlorides.
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