Which ester in each pair would be expected to undergo saponification at the faster rate? W...

Which ester in each pair would be expected to undergo saponification at the faster rate? Why?

(a)

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(b)

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(c)

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(d)

Sample Solution (a) p-Nitrophenyl acetate reacts faster. A p-nitrophenyl group withdraws electrons from the ester oxygen which decreases its ability to stabilize the carbonyl group. A less-stabilized carbonyl is more reactive than a more-stabilized one.