Question

Relative rate of alkaline hydrolysis of the following compound: 4-R-ethyl benzoate where R is: (A) $NO_2$, (B) $Cl$, (C) $H$, (D) $CH_3$, (E) $OCH_3$

• A. A $>$ B $>$ C $>$ D $>$ E
• B. A $>$ E $>$ C $>$ B $>$ D
• C. A $<$ B $<$ C $<$ D $<$ E
• D. A $<$ E $<$ B $<$ C $<$ D

Hint:

For nucleophilic attacks, EWGs are like magnets—they pull electrons away, making the center more attractive to the nucleophile.

Answer 1

The Correct Option is A

Step 1: Concept Alkaline hydrolysis of esters involves the attack of $OH^-$ on the carbonyl carbon. Electron-withdrawing groups (EWGs) increase the rate, while electron-donating groups (EDGs) decrease it.

Step 2: Meaning EWGs make the carbonyl carbon more electrophilic.

Step 3: Analysis $NO_2$ is a strong EWG (-I, -M), $Cl$ is a weak EWG (-I $>$ +M), $H$ is the reference, $CH_3$ is a weak EDG (+I, +H), and $OCH_3$ is a strong EDG (+M).

Step 4: Conclusion The rate order follows the order of electron-withdrawing strength: $NO_2 > Cl > H > CH_3 > OCH_3$, which matches option 1. Final Answer: (1)