Aldehydes, Ketones and Carboxylic Acids
MCQ Quiz
1. Aldehydes without α-hydrogen atoms undergo which reaction in the presence of concentrated alkali?
Correct Answer: (b) Cannizzaro reaction
(Aldehydes without α-hydrogen undergo Cannizzaro reaction in concentrated alkali.)
2. Which of the following compounds will give a positive Haloform test?
Correct Answer: (b) Acetone
(Methyl ketone group gives positive Haloform test.)
3. The carbonyl group in aromatic aldehydes and ketones is:
Correct Answer: (d) Deactivating and meta-directing
(Carbonyl is electron-withdrawing, hence deactivates and directs meta.)
4. Which reagent reacts with both aldehydes and ketones to form a yellow, orange, or red precipitate, used for their general detection?
Correct Answer: (d) 2,4-Dinitrophenylhydrazine (2,4-DNP)
(2,4-DNP reacts with both aldehydes and ketones for detection.)
5. In aldol condensation, the α-hydrogens are acidic due to the electron-withdrawing effect of the:
Correct Answer: (c) Carbonyl group
(α-Hydrogens are acidic due to electron-withdrawing carbonyl.)
6. The reduction of an aldehyde with LiAlH4 produces a:
Correct Answer: (c) Primary alcohol
(LiAlH4 reduces aldehydes to primary alcohols.)
7. Which of the following is an example of an α,β-unsaturated carbonyl compound formed during aldol condensation followed by dehydration?
Correct Answer: (c) But-2-enal
(Aldol condensation and dehydration gives α,β-unsaturated carbonyl, e.g. but-2-enal.)
8. The conversion of an aldehyde to a carboxylic acid is an example of:
Correct Answer: (b) Oxidation
(Aldehyde to acid involves oxidation.)
9. Which of the following reagents is a weak nucleophile?
Correct Answer: (c) H2O
(Water is a weak nucleophile.)
10. The Gattermann-Koch reaction is used to prepare:
Correct Answer: (c) Aromatic aldehydes
(Gattermann-Koch reaction forms aromatic aldehydes.)
11. Which of the following statements about α-hydrogens in aldehydes and ketones is TRUE?
Correct Answer: (a) They are highly acidic.
(α-Hydrogens are acidic near carbonyl.)
12. The Etard reaction is specific for the synthesis of:
Correct Answer: (b) Aromatic aldehydes
(Etard reaction synthesizes aromatic aldehydes.)
13. In the Cannizzaro reaction, one molecule of aldehyde is oxidized, and another is:
Correct Answer: (c) Reduced
(In Cannizzaro, one molecule is reduced to alcohol.)
14. Ketones generally do not undergo oxidation under mild conditions because:
Correct Answer: (c) No hydrogen atoms directly attached to the carbonyl carbon
(Ketones lack these H, so no mild oxidation.)
15. In a cross-aldol condensation between two different carbonyl compounds, the maximum number of aldol products possible is typically:
Correct Answer: (d) 4
(Maximum 4 aldol products from cross-condensation.)
16. The carbonyl carbon in aldehydes and ketones is:
Correct Answer: (b) sp2 hybridized
(Carbonyl carbon is sp2 hybridized.)
17. Aldehydes and ketones are isomers. What type of isomerism do they often exhibit?
Correct Answer: (c) Functional isomerism
(Aldehyde and ketone can be functional isomers.)
18. Primary alcohols can be oxidized to aldehydes using:
Correct Answer: (c) PCC (Pyridinium Chlorochromate)
(PCC oxidizes alcohol to aldehyde.)
19. When a Grignard reagent (RMgX) reacts with formaldehyde, the product formed after hydrolysis is a:
Correct Answer: (a) Primary alcohol
(Grignard with formaldehyde gives primary alcohol.)
20. The reaction of benzene with an acyl chloride in the presence of anhydrous AlCl3 is known as:
Correct Answer: (c) Friedel-Crafts acylation
(Acyl chloride & AlCl3 in benzene: Friedel-Crafts acylation.)
21. Which of the following is the most reactive towards nucleophilic addition reactions?
Correct Answer: (b) Acetaldehyde
(Acetaldehyde is the most reactive for nucleophilic addition.)
22. The product formed when hydrogen cyanide (HCN) adds to acetaldehyde is a:
Correct Answer: (c) Cyanohydrin
(HCN adds to aldehyde to form cyanohydrin.)
23. Which reagent is used to reduce a carbonyl group (C=O) to a methylene group (−CH2−) under acidic conditions?
Correct Answer: (c) Zn−Hg/HCl (Clemmensen reduction)
(Clemmensen reduction converts carbonyl to methylene under acid.)