Chapter 20: Carboxylic Acids and their Derivatives – 200
Multiple-Choice Questions with Answers and
Explanations
1. Which functional group characterizes a carboxylic acid?
a) -OH
b) -CHO
c) -COOH
d) -COOR
Answer: c) -COOH
Explanation: The carboxyl group (-COOH) consists of a carbonyl (C=O) and a hydroxyl (-OH) on the same
carbon.
2. What is the IUPAC name for CH₃CH₂CH₂COOH?
a) Butanoic acid
b) Propanoic acid
c) Pentanoic acid
d) Butanal
Answer: a) Butanoic acid
Explanation: Four-carbon straight chain with -COOH gives butanoic acid.
3. Which of the following is the strongest acid?
a) CH₃CH₂OH
b) CH₃COOH
c) CH₃CH₂NH₂
d) CH₃OCH₃
Answer: b) CH₃COOH
Explanation: Carboxylic acids (pKa ~4-5) are much stronger than alcohols, ethers, or amines.
,4. The pKa of a typical carboxylic acid is approximately:
a) 0-1
b) 4-5
c) 9-10
d) 15-16
Answer: b) 4-5
Explanation: Acetic acid pKa = 4.76; electron-withdrawing groups lower it further.
5. What product forms when a carboxylic acid reacts with NaOH?
a) An ester
b) An alcohol
c) A carboxylate salt + water
d) An acid chloride
Answer: c) A carboxylate salt + water
Explanation: RCOOH + NaOH → RCOO⁻Na⁺ + H₂O (acid-base neutralization).
6. Which reagent converts a carboxylic acid to an acid chloride?
a) H₂SO₄
b) SOCl₂
c) NaBH₄
d) KOH
Answer: b) SOCl₂
Explanation: Thionyl chloride replaces OH with Cl; byproducts SO₂ and HCl are gases.
7. Reduction of a carboxylic acid with LiAlH₄ gives:
a) An aldehyde
b) A ketone
c) A primary alcohol
,d) An alkane
Answer: c) A primary alcohol
Explanation: LiAlH₄ reduces RCOOH to RCH₂OH; NaBH₄ does not reduce carboxylic acids.
8. Fischer esterification produces an ester from a carboxylic acid and:
a) An alcohol (with acid catalyst)
b) An amine
c) An acid chloride
d) A Grignard reagent
Answer: a) An alcohol (with acid catalyst)
Explanation: RCOOH + R'OH ⇌ RCOOR' + H₂O, catalyzed by H⁺.
9. Which of the following is NOT a carboxylic acid derivative?
a) Acid chloride
b) Amide
c) Aldehyde
d) Anhydride
Answer: c) Aldehyde
Explanation: Derivatives include acid chlorides, anhydrides, esters, amides, nitriles.
10. What is the product of heating a carboxylic acid with P₂O₅?
a) An ester
b) An acid anhydride
c) An amide
d) A ketone
Answer: b) An acid anhydride
Explanation: Two molecules of RCOOH lose water to form (RCO)₂O (symmetrical anhydride).
11. The IUPAC name for (CH₃)₂CHCOOH is:
, a) Butanoic acid
b) 2-Methylpropanoic acid
c) 2,2-Dimethylethanoic acid
d) Isopropanoic acid
Answer: b) 2-Methylpropanoic acid
Explanation: Three-carbon chain with methyl on C2; common name is isobutyric acid.
12. Benzoyl chloride is derived from which carboxylic acid?
a) Benzoic acid
b) Benzyl alcohol
c) Benzaldehyde
d) Phenol
Answer: a) Benzoic acid
Explanation: C₆H₅COCl from C₆H₅COOH via SOCl₂.
13. Which reagent reduces an ester to a primary alcohol?
a) NaBH₄
b) LiAlH₄
c) H₂/Pd
d) KMnO₄
Answer: b) LiAlH₄
Explanation: LiAlH₄ reduces esters to two primary alcohols (RCH₂OH + R'OH).
14. Reaction of an acid chloride with excess primary amine yields:
a) An amide + amine salt
b) An ester
c) A carboxylic acid
d) A nitrile
Answer: a) An amide + amine salt
Multiple-Choice Questions with Answers and
Explanations
1. Which functional group characterizes a carboxylic acid?
a) -OH
b) -CHO
c) -COOH
d) -COOR
Answer: c) -COOH
Explanation: The carboxyl group (-COOH) consists of a carbonyl (C=O) and a hydroxyl (-OH) on the same
carbon.
2. What is the IUPAC name for CH₃CH₂CH₂COOH?
a) Butanoic acid
b) Propanoic acid
c) Pentanoic acid
d) Butanal
Answer: a) Butanoic acid
Explanation: Four-carbon straight chain with -COOH gives butanoic acid.
3. Which of the following is the strongest acid?
a) CH₃CH₂OH
b) CH₃COOH
c) CH₃CH₂NH₂
d) CH₃OCH₃
Answer: b) CH₃COOH
Explanation: Carboxylic acids (pKa ~4-5) are much stronger than alcohols, ethers, or amines.
,4. The pKa of a typical carboxylic acid is approximately:
a) 0-1
b) 4-5
c) 9-10
d) 15-16
Answer: b) 4-5
Explanation: Acetic acid pKa = 4.76; electron-withdrawing groups lower it further.
5. What product forms when a carboxylic acid reacts with NaOH?
a) An ester
b) An alcohol
c) A carboxylate salt + water
d) An acid chloride
Answer: c) A carboxylate salt + water
Explanation: RCOOH + NaOH → RCOO⁻Na⁺ + H₂O (acid-base neutralization).
6. Which reagent converts a carboxylic acid to an acid chloride?
a) H₂SO₄
b) SOCl₂
c) NaBH₄
d) KOH
Answer: b) SOCl₂
Explanation: Thionyl chloride replaces OH with Cl; byproducts SO₂ and HCl are gases.
7. Reduction of a carboxylic acid with LiAlH₄ gives:
a) An aldehyde
b) A ketone
c) A primary alcohol
,d) An alkane
Answer: c) A primary alcohol
Explanation: LiAlH₄ reduces RCOOH to RCH₂OH; NaBH₄ does not reduce carboxylic acids.
8. Fischer esterification produces an ester from a carboxylic acid and:
a) An alcohol (with acid catalyst)
b) An amine
c) An acid chloride
d) A Grignard reagent
Answer: a) An alcohol (with acid catalyst)
Explanation: RCOOH + R'OH ⇌ RCOOR' + H₂O, catalyzed by H⁺.
9. Which of the following is NOT a carboxylic acid derivative?
a) Acid chloride
b) Amide
c) Aldehyde
d) Anhydride
Answer: c) Aldehyde
Explanation: Derivatives include acid chlorides, anhydrides, esters, amides, nitriles.
10. What is the product of heating a carboxylic acid with P₂O₅?
a) An ester
b) An acid anhydride
c) An amide
d) A ketone
Answer: b) An acid anhydride
Explanation: Two molecules of RCOOH lose water to form (RCO)₂O (symmetrical anhydride).
11. The IUPAC name for (CH₃)₂CHCOOH is:
, a) Butanoic acid
b) 2-Methylpropanoic acid
c) 2,2-Dimethylethanoic acid
d) Isopropanoic acid
Answer: b) 2-Methylpropanoic acid
Explanation: Three-carbon chain with methyl on C2; common name is isobutyric acid.
12. Benzoyl chloride is derived from which carboxylic acid?
a) Benzoic acid
b) Benzyl alcohol
c) Benzaldehyde
d) Phenol
Answer: a) Benzoic acid
Explanation: C₆H₅COCl from C₆H₅COOH via SOCl₂.
13. Which reagent reduces an ester to a primary alcohol?
a) NaBH₄
b) LiAlH₄
c) H₂/Pd
d) KMnO₄
Answer: b) LiAlH₄
Explanation: LiAlH₄ reduces esters to two primary alcohols (RCH₂OH + R'OH).
14. Reaction of an acid chloride with excess primary amine yields:
a) An amide + amine salt
b) An ester
c) A carboxylic acid
d) A nitrile
Answer: a) An amide + amine salt
