Organic Chemistry Questions and Answers - Alcohols as Acids

This set of Organic Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Alcohols as Acids”.

1. CH₃OH is a which type of acid?
a) Bronsted acid
b) Lewis acid
c) Arrhenius acid
d) Lewis and Arrhenius acid
View Answer

Answer: a
Explanation: Alcohols are very weak Bronsted acids with pKa values generally in the range of 15 – 20. Because the hydroxyl proton is the most electrophilic site, proton transfer is the most important reaction to consider with nucleophiles.

2. Which of the following is more acidic than alcohols?
a) Arrhenius acid
b) amine
c) alkyne
d) carboxylic acid
View Answer

Answer: d
Explanation: As there will be resonance between -COO^–. So, it will be more stable and acidic than -OH.

3. What is the correct order of acidic strength?

a) I > II > III
b) II > I > III
c) III > II > I
d) I > III > II
View Answer

Answer: b
Explanation: Inductive effect (+I) destabilises phenol ion and III has maximum +I effect and in II -CH₃ is at meta position so no effect on phenol ion negative charge.

4. Which of the following is more acidic alcohol?
a) Phenol
b) Cyclohexanol
c) Methanol
d) Ethanol
View Answer

Answer: a
Explanation: Resonance stabalizes the negative charge in phenol ion, negative charge is moving throughout. So, phenol is more acidic.

5. What is the correct order of acidic strength?

a) I > II > III
b) III > II > I
c) II > III > I
d) I > III > II
View Answer

Answer: c
Explanation: Inductive effect (-I) stabilises phenol ion and II has maximum -I effect. But at para and ortho position +M effect will also show effect so they are les acidic than meta.

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6. What is the correct order of acidic strength?

a) I > II > III
b) III > II > I
c) II > III > I
d) I > III > II
View Answer

Answer: b
Explanation: Inductive effect (-I) stabilises phenol ion and II has maximum -I effect. Less the distance between electron withdrawing group and negative charge more the stability and acidity too.

7. What is the correct order of acidic strength?
a) CH₃-OH
b) CH₃CH₂-OH
c) CH₃ CH₂ CH₂-OH
d) CH₃ CH₂ CH₂ CH₂-OH
View Answer

Answer: a
Explanation: Inductive effect (+I) destabilises -OH ion, so CH₃-OH is most acidic alcohol among above, as it has least +I.

8. What is the correct order of acidic strength?

a) I > II > III
b) III > II > I
c) II > III > I
d) I > III > II
View Answer

Answer: d
Explanation: Electron withdrawing group stabalises phenol ion. More the -M effect, more the stability.

9. What is the correct order of acidic strength?

a) I > II > III
b) III > II > I
c) II > III > I
d) I > III > II
View Answer

Answer: a
Explanation: Electron withdrawing group stabalises phenol ion and electron donating group destablises it. More the -M effect, more the stability, so I is most stable and acidic.

10. What is the correct order of acidic strength?

a) I > II > III
b) III > II > I
c) II > I > III
d) I > III > II
View Answer