Arrange the following alcohols in decreasing order of acidity:
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D), (A), (C), (B)
An alcohol is acidic because the O–H bond is polar. An alkyl group releases electrons (+I effect) towards the oxygen. This makes the O–H bond less polar and destabilises the alkoxide ion left after the proton is lost, so every extra alkyl group on the carbinol carbon lowers the acidity:
\( \displaystyle \ce{CH3OH} \gt \text{primary} \gt \text{secondary} \gt \text{tertiary} \)
Matching the labels to the compounds:
(A) \( \ce{CH3CH2OH} \): ethanol (primary, one alkyl group on the carbinol carbon)
(B) \( \ce{(CH3)3COH} \): 2-methylpropan-2-ol, tert-butyl alcohol (tertiary, three alkyl groups)
(C) \( \ce{(CH3)2CHOH} \): propan-2-ol (secondary, two alkyl groups)
(D) \( \ce{CH3OH} \): methanol (no alkyl group on the carbinol carbon)
Shortcut: Methanol has no alkyl group on the carbinol carbon, so it must come first; only Option (4) starts with (D).
NCERT (2026-27 edition):
Acidity of Alcohols
