Rank the following compounds in the order of increasing acidity.

• A. c < d < a < b
• B. d < a < b < c
• C. b < a < d < c

Answer: (B)

Verified step by step guidance

1. Identify the functional groups in each compound: a) primary amine, b) lactone (cyclic ester), c) carboxylic acid, d) quaternary ammonium salt.
2. Recall the general acidity order of functional groups: carboxylic acids are more acidic than esters, which are more acidic than amines. Quaternary ammonium salts are not acidic.
3. Analyze the structure of each compound: a) isopropylamine, b) caprolactone, c) acrylic acid, d) trimethylammonium ion.
4. Consider the stability of the conjugate base: c) carboxylate ion is stabilized by resonance, b) lactone has no acidic hydrogen, a) amine has a lone pair on nitrogen, d) quaternary ammonium has no acidic hydrogen.
5. Rank the compounds based on acidity: d) is least acidic (no acidic hydrogen), a) is next (amine), b) follows (lactone), and c) is most acidic (carboxylic acid).