Chemistry Reference
In-Depth Information
theory (DFT) calculations on the reactions of
1
O
2
with other amino acids may
provide further information on the potential role of
1
O
2
in the functioning of
the cell.
4.3 OZONE
Ozone (O
3
) is an allotrope of oxygen, which provides a protective shield to
incoming UV radiation in the stratosphere. However, it is one of the most
dangerous phytotoxic air pollutants in the troposphere. Thus, O
3
is associated
with several health effects including exacerbation of asthma and airway inflam-
mation and hyperreactivity [205, 206]. O
3
appears to be the source of degrada-
tion of self-assembled alkanethiol monolayers on silver and gold surfaces that
are exposed to ambient air [207, 208]. O
3
is also damaging to plant life, which
ranges from inhibition of photosynthesis and associated yield loss to prema-
ture senescence and visible tissue necrosis [209]. The formation of O
3
by
human neutrophils may contribute to killing bacteria [210]. Met, cys, His, and
Trp were demonstrated to produce O
3
from
1
O
2
in the water oxidation pathway
[210]. In the aqueous phase, O
3
has applications in water treatment, whitening,
and disinfection [211-213]. Ozone is unstable in the aqueous phase and decom-
poses through several initiation, propagation, and termination chain reactions,
initiated by hydroxide ions [214-221]. The decomposition of O
3
depends on
proton concentration, alkalinity, and inorganic and organic constituents of
water. Studies have shown the acceleration of the decomposition of ozone with
increasing pH and hydrogen peroxide [217] The following set of reactions are
involved in the decomposition of O
3
[211]:
O OH
+
−
→
HO O
−
+
k
=
70
/M/s
(4.41)
3
2
2
41
O HO
+
−
→
•
OH O
+
•−
+
O
k
=
2 8 10
.
×
6
/M/s
(4.42)
3
2
2
2
42
O O
+
•−
→
O
•−
+
O
k
=
1 6 10
.
×
9
/M/s
(4.43)
3
2
3
2
43
pH < ≈8:
O
•−
+
H
+
HO
•
k
=
5 0 10
.
×
10
/M/s
(4.44)
3
3
44
k
-
=
3 3 10
.
×
2
/s
44
HO
•
→
•
OH O
+
k
=
1 4 10
.
×
5
/s
(4.45)
3
2
45
pH > ≈8:
•−
•−
+
3
(4.46)
O
O
O
k
=
2 1 10
.
×
/s
3
2
46
k
-
=
3 3 10
.
×
9
/s
46
•
OH O
+ →
HO O
•
+
k
=
1 0 10
.
×
8
−
2 0 10
.
×
9
/M/s
.
(4.47)
3
2
2
47
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