Page 729 - Advanced Organic Chemistry Part A - Structure and Mechanisms, 5th ed (2007) - Carey _ Sundberg

N NH 711
H 2 2
X C O X O H
O H O H PROBLEMS
H
O – H O
A B X = H, NO 2

7.30. The hydrolysis of the ester group in 2-acetoxybenzaldehyde is accelerated by
4
about 10 , relative to the 4-isomer. The rate of hydrolysis in the pH range
6.0–8.5 follows the rate expression

Rate = k +k OH
−
0
Both the k and k OH terms are larger than for the 4-isomer. When the
−
0
hydrolysis is carried out in 18 O-labeled water, the acetic acid contains 50%
18 O. Suggest a mechanism that is consistent with these observations.
7.31. The pH-rate profile for the hydrolysis of 4-nitrophenyl 2-aminobenzoate is
given in Figure 7.13 (p. 674). The reaction exhibits a solvent isotope effect
of ∼ 0.5 in D O. Suggest possible mechanisms for the reaction, based on the
2
shape of the pH-rate profile and chemical structure considerations. Derive the
kinetic expression for the most likely mechanism.