Which of the following carboxylic acids undergoes decarboxylation most easily ?

Options

A. `CH_(3)COCO_(2)H`
B. `CH_(3)COCH_(2)CO_(2)H`
C. `C_(6)H_(5)CO_(2)H`
D. `CH_(3)CH_(2)CO_(2)H`

Answer

B

Explanation

`RCOOHoverset("Decarboxylation")rarrR-H+CO_(2)`
Althought the unusual stability of `CO_(2)` means that the decarboxylation of most acids is exothermic, in practice, the reaction is not always easy to carry out because the reaction is very slow. Special group usually have to be present in the molecule for decarboxylate readily when they are heated to `100-150^(@)C`. Some `beta-keto` acids even decarboxylates, it forms a resonancep-stabilized enolate anion:

(2) When the acid itself decarboxulates, it goes through a `6`-membered cyclic transition state: