Q.15 The acid that undergoes decarboxylation most readily upon heating is
Question Statement
Which of the following acids undergoes decarboxylation most readily upon heating?
Core Concept: Decarboxylation Rule
-
β-keto acids (–CO–CH₂–COOH) and β-dicarboxylic acids decarboxylate very easily on heating.
-
This is because they form a stable six-membered cyclic transition state, releasing CO₂ smoothly.
-
Simple aromatic acids or α-hydroxy acids do not decarboxylate easily.
Option-by-Option Analysis
Option (A): Ph–CO–COOH (α-keto acid)
-
This is an α-keto acid.
-
α-keto acids can decarboxylate, but less readily than β-keto acids.
-
❌ Not the most favorable case.
Option (B): Ph–COOH (Benzoic acid)
-
A simple aromatic carboxylic acid.
-
No β-carbonyl group → no cyclic transition state.
-
Requires very harsh conditions for decarboxylation.
-
❌ Least reactive.
Option (C): Ph–CO–CH₂–COOH (β-keto acid) ✅ Correct Answer
-
This is a β-keto acid (benzoylacetic acid).
-
Contains the crucial –CO–CH₂–COOH unit.
-
On heating:
-
Forms a six-membered cyclic transition state
-
Loses CO₂ easily
-
Produces a stable ketone
-
-
✔️ Decarboxylates most readily.
Option (D): Ph–CH(OH)–CH₂–COOH (β-hydroxy acid)
-
This is a β-hydroxy acid.
-
More likely to undergo dehydration, not decarboxylation.
-
❌ Does not favor CO₂ loss.
Final Answer
Option (C) — β-keto acid (Ph–CO–CH₂–COOH) decarboxylates most readily on heating.
SEO-Optimized Introduction
Understanding which acid undergoes decarboxylation most readily upon heating is a key concept in organic chemistry. This reaction depends strongly on molecular structure, especially the presence of a β-keto group. In this article, we analyze each option and explain why β-keto acids decarboxylate easily compared to other carboxylic acids.
Why β-Keto Acids Decarboxylate Easily
-
Formation of six-membered cyclic transition state
-
Release of stable CO₂ gas
-
Formation of resonance-stabilized enol/ketone
-
Lower activation energy
Keywords Used Naturally
-
acid undergoes decarboxylation most readily
-
decarboxylation on heating
-
beta keto acid decarboxylation
-
benzoylacetic acid reaction
-
organic chemistry decarboxylation
