Question

Which of the following compounds will decarboxylate when heated?

Short answer

Compound showing decarboxylation is compound A and D, and E.

Step-by-step solution

Decarboxylation of compound (A)

The given compound (A) is a beta-keto acid with the carbonyl carbon at the third position from the carbon with the carboxylic acid. Thus, when the CO₂group is removed, the electrons left behind are delocalized into the carbonyloxygen.

Therefore, compound (a), when it forms carboxylate ions with a carbonyl group at the 3-position, loses CO₂ when heated, known as decarboxylation.

Decarboxylation of compound (B)

The given compound (b) is not beta-keto acid. Itdoes not have the carboxyl group. Therefore, removing carbon dioxide (CO₂) is not possible on heating. Thus, compound (B) does not show decarboxylation.

Decarboxylation of compound (C)

The given compound (C) is a dioic acid with the carboxylate group at 1st and 4th positions; thus, when the CO₂group is removed, the electrons left behind arenot delocalized into the carbonyloxygen.

Therefore, compound (C), when it forms carboxylate ions with a carbonyl group at the 3-position, does not loose CO₂upon heating; no decarboxylation occurs in compound (C).

Decarboxylation of compound (D)

The given compound (D) is a beta-keto acid. The carbonyl carbon at the third position from the carbon having the carboxylic acid; thus, when the CO₂group is removed, the electrons left behind are delocalized into the carbonyloxygen.

Therefore, compound (D), when it forms carboxylate ions with a carbonyl group at the 3-position, loses CO₂ when heated, known as decarboxylation.

Decarboxylation of compound (E)

The given compound (E) has two carbonyl groups and one carboxylate group, one in the third position and one in the fourth position. The electrons left behind are delocalized into the 3rd carbonyl oxygen when the carbon dioxide group (CO₂) is removed.

Therefore, compound (E), when it forms carboxylate ions with a carbonyl group at the 3-position, loses CO₂ when heated, known as decarboxylation.