Chemistry Reference
In-Depth Information
This problem relies entirely on inductive effects. Realizing that fluorine is more elec-
tronegative than oxygen, the order of deprotonation is as follows:
9. Which proton is the most acidic? Rationalize your answer.
The pK
a
value of a proton adjacent to a ketone carbonyl is approximately 20-25. The
pK
a
value of a carboxylic acid is approximately 4.75. Using the same calculations
presented in the solution for Problem 8(a), the pK
a
value of the protons between the
ketone and the carboxylic acid is approximately 11.25-13.75. Since the acidity of a
proton increases as its pK
a
value decreases, the most acidic proton belongs to the
carboxylic acid.
10. Using the pK
a
values given in Appendix 1, calculate the equilibrium constants for the
following reactions:
Recall from general chemistry that the equilibrium constant, K
eq
, for a given reaction is
defined as
Also, recall that the definition of the acid dissociation constant, K
a
,is
Finally, we recognize, as shown, that an acid-base equilibrium consists of two related
reactions for which K
a
values can be calculated and that at equilibrium, the [H
รพ
]is
equivalent for each equation.
