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Directions: The decarboxylation of aromatic acids is most often carried out by heating with Cu-quinoline \[ArCOOH\xrightarrow[{}]{Cu-quinoline}ArH+C{{O}_{2}}\] Cuprous salts of aromatic acids, actually undergoes decarboxylation. However, two other methods can be used with certain substrates.

Method 1: Salt of acid, \[ArCO{{O}^{-}}\]is heated (SE1)

Step I:

Step II:

Method II: Carboxylic acid is heated with a strong acid, often sulphuric acid.

Decarboxylation takes place by the arenium ion mechanism, with\[{{\text{H}}^{+}}\] electrophile. Evidently, the order of electrofugal ability is \[C{{O}_{2}}>{{H}^{+}}>COO{{H}^{+}}\]Rearrangements are also known to take place. For example,, when the phthalate ion is heated with catalytic amount of cadmium, the terephthalate ion is produced. In a similar process, potassium benzoate heated with cadmium salts disproportionates. The rearrangement is named as 'Henkel rearrangement'.

Mark out the correct order of -G (functional group) according to their ease to facilitate the decarboxylation reaction.

A) \[-OC{{H}_{3}}>-N{{O}_{2}}>-F>-H>-C{{H}_{3}}\]

B) \[-N{{O}_{2}}>-F>-H>-C{{H}_{3}}>-OC{{H}_{3}}\]

C) \[-N{{O}_{2}}>-F>-OC{{H}_{3}}>-H>-C{{H}_{3}}\]

D) \[-OC{{H}_{3}}>-C{{H}_{3}}>-H>-F>-N{{O}_{2}}\]

Correct Answer: C

Solution :

                is stabilised by inductive effect only. Greater the stability of carbanion, greater the ease of decarboxylation.