Chemistry Reference
In-Depth Information
The rate constants for the reactions of
CO
•−
with organic compounds were
used to derive the quantitative structure-activity relationships (QSARs) (Eqs.
5.8-5.10) [51]:
Monosubstituted benzene derivatives:
+
2
(5.8)
log
k
=
3 4 0 8
. (
±
. )
−
3 6 0 8
. (
±
. )
σ
p
n
=
7
,
r
=
0 96
.
,
s
=
0 45
.
p
-Substituted phenoxide ions:
log
k
=
8 40 0 02
.
(
±
.
)
−
0 91 0 03
.
(
±
.
)
σ
p
+
n
=
8
,
r
2
=
0 999
.
,
s
=
0 019
.
(5.9)
p
-Substituted anilines:
log
k
=
8 710 0 06
.
(
±
.
)
−
0 98 0 15
.
(
±
.
)
σ
p
+
n
=
7
,
r
2
=
0 98
.
,
s
=
0 052
.
.
(5.10)
The relationships of the rate constants with molar gibbs free energy change
of electron transfer were obtained for
p
-substituted phenoxide ions and ani-
lines (Fig. 5.5) [51]. The reaction with aniline was approximately one order
of magnitude faster than the phenoxide ions, which is expected if reactions
take place through inner-sphere mechanism [51]. This is supported by an
earlier study in which low activation energies of reactions of
CO
•−
with organic
compounds were determined [40]. This further suggests that gibbs molar
9.2
Anilines
Phenoxide ions
9.0
8.8
8.6
8.4
8.2
8.0
7.8
7.6
-120
-100
-80
-60
-40
-20
0
∆
G
°
(kJ/mol)
Figure 5.5.
Linear correlations of rate constants for the oxidation of substituted phen-
oxide anions and anilines by the carbonate radical. Regression lines correspond to the
following equations: (1) for phenoxide ions, log
k
= 6.8(±0.4) − 0.021(±0.005) Δ
G
°′
(
n
= 8,
r
2
= 0.94,
s
= 0.12), and (2) for anilines, log
k
= 6.9(±0.3) − 0.030(±0.006) Δ
G
°′
(
n
= 7,
r
2
= 0.97,
s
= 0.07) (adapted from Canonica and Tratnyek [51] with the permis-
sion of the Society of Environmental Toxicology and Chemistry).
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