What will be the product isolated after thermal decarboxylation of each of the following?...

What will be the product isolated after thermal decarboxylation of each of the following? Using curved arrows, represent the bond changes that occur in the decarboxylation step.

(a)

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(b)

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(c)

Sample Solution

(a) Thermal decarboxylation of malonic acid derivatives leads to the replacement of one of the carboxyl groups by a hydrogen.

In this particular case, the reaction was carried out at the temperature indicated and gave the product shown in 96–99% yield.

The transition state for decarboxylation incorporates a cyclic array of six atoms and gives the enol form of the product as an intermediate: