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GATE 2021 CY – Question 14

Organic Chemistry · General Concepts: Structure dependence on properties such as basicity and acidity. Role of aromatic stability on physical properties of organic compounds. · 1 mark · Multiple choice

The least acidic among the following compounds is:

Diagram for GATE 2021 CY question 14
  1. M
  2. N
  3. O
  4. P

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Correct answer: (A) M

Explanation

M is a terminal alkyne, N a carboxylic acid, O a phenol and P a sulfonic acid. Even though the ester substituent increases the acidity of M relative to an unsubstituted alkyne, its acetylide conjugate base remains less stabilized than phenoxide, carboxylate or sulfonate. Typical acidity increases in that sequence, so the least acidic compound is **M, A**.