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from deprotonation, thus decreasing its acidity and raising its pK
a
. In actuality, the
pK
a
of p-methoxyaniline is 5.34, thus supporting the conclusion of this problem.
h. p-Cl
The structure of p-chloroaniline is shown below with partial charges assigned to
the ring system. Because the electron-donating chloro group is located para to the
amine, electron density is increased adjacent to the amine functionality, effectively
rendering the aromatic ring electron donating para to the chloro group. An
electron-donating group attached to an amine destabilizes the anion resulting from
deprotonation, thus decreasing its acidity and raising its pK
a
. In actuality, the pK
a
of p-chloroaniline is 4.15, reflecting the electron-withdrawing nature of the chloro-
phenyl group.
i. m-Cl
The structure of m-chloroaniline is shown below with partial charges assigned to the
ring system. Because the electron-donating chloro group is located meta to the amine,
electron density is decreased adjacent to the amine functionality, effectively
rendering the aromatic ring electron withdrawing meta to the chloro group. An
electron-withdrawing group attached to an amine stabilizes the anion resulting
from deprotonation, thus increasing its acidity and lowering its pK
a
. In actuality,
the pK
a
of m-chloroaniline is 3.46, thus supporting the conclusion of this problem.
