Dolbier HW Solutions 511 - 605 AMINES 22.4 The...

AMINES
605
22.4 The electron-donating amino group and the electron-withdrawing nitro group are directly conjugated
in p -nitroaniline. The planar geometry of p -nitroaniline suggests that the delocalized resonance form
shown is a major contributor to the structure of the compound.
22.5 The p K
b
of an amine is related to the equilibrium constant K
b
by
p K
b
log K
b
The p K
b
of quinine is therefore
p K
b
log (1 10 6 ) 6
the values of K
b
and p K
b
for an amine and K
a
and p K
a
of its conjugate acid are given by
K
a
K
b
1 10 14
and
p K
a
p K
b
14
The values of K
a
and p K
a
for the conjugate acid of quinine are therefore
K
a
1 10
8
and
p K
a
14 p K
b
14 6 8
22.6 The Henderson – Hasselbalch equation described in Section 19.4 can be applied to bases such as
amines, as well as carboxylic acids. The ratio [CH
3
NH
3
] [CH
3
NH
2
] is given by
The ionization constant of methylammonium ion is given in the text as 2