MCQs on Aldol Condensation

Aldol condensation is a condensation reaction of aldehydes and ketones with at least one alpha hydrogen. It leads to the formation of β-hydroxy aldehydes (aldol) or β-hydroxy ketones (ketol), which readily undergo dehydration to give α,β-unsaturated carbonyl compounds. Dilute alkali acts as a catalyst. When the two different aldehydes and ketones condense, it is called cross aldol condensation.

1. When an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxy aldehyde or β-hydroxy ketone followed by dehydration to give a conjugated enone, it is called

(a) Claisen condensation

(b) Aldol condensation

(c) Knoevenagel condensation

(d) Henry condensation

2. Which of the following will not undergo aldol condensation?

(a) CH3COCH3

(b) CH3CHO

(c) CH3CH2CHO

(d) HCHO

3. Carbon-carbon bonds are not formed in which of the following reactions?

(a) Cannizzaro reaction

(b) Reimer-Tiemann reaction

(c) Wurtz reaction

(d) Aldol condensation

4. Which of the following compounds will most readily undergo nucleophilic attack?

(a) CH3CONH2

(b) CH3COOCH3

(c) CH3COCl

(d) CH3COOCOCH3

5. Acetaldehyde does not react with

(a) electrophiles

(b) free radicals

(c) nucleophiles

(d) both (a) and (b)

6. Which of the following statements is incorrect for aldol condensation reaction?

(a) The first step is deprotonation at the α-Hydrogen position

(b) An aldol reaction occurs between two aldehydes or ketones, and at least one reactant must contain an α-Hydrogen atom

(c) The product of an aldol reaction between two aldehydes is a β-diketone

(d) An aldol reaction is a C–C bond-forming reaction

7. Which of the following compounds does not undergo aldol condensation?

(a) 2-Methylpentanal

(b) Phenyl acetaldehyde

(c) 1-Phenylpropanone

(d) Benzaldehyde

8. Which of the following is formed when acetaldehydes react in the presence of dil. NaOH?

(a) Resinous mass

(b) Sodium acetate

(c) Ethyl acetate

(d) Aldol

9. Which of the following will undergo self aldol condensation in the presence of dil. NaOH?

(a) CH2 = CHCHO

(b) CH ≡ C-CHO

(c) CH3CH2CHO

(d) C6H5CHO

10. Which among the following do not undergo aldol condensation?

1. 2-phenylethanal

2. trichloroethanal

3. benzaldehyde

4. ethanal

5. propanal

(a) 2 and 3 only

(b) 1, 2 and 3 only

(c) 2, 3 and 5 only

(d) 3 and 4 only

Answer

1. (b)

2. (d)

3. (a)

4. (c)

5. (d)

6. (c)

7. (d)

8. (d)

9. (c)

10. (a)

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