 Solution

ID: past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-4/66/a/ii/solution

lo g (k_{X} / k_{H}) = ρ σ_{X}

. The positive slope,

ρ = + 1.97

, means electron-withdrawing para substituents accelerate hydrolysis. They increase carbonyl electrophilicity and stabilize the additional negative charge associated with the addition transition state/tetrahedral intermediate. Strong electron donation has the opposite effect. Hydroxide addition to the acyl carbon, followed by tetrahedral-intermediate collapse and aryloxide loss, is consistent with both this trend and the bimolecular rate law.

 New to topics? Read the docs here!