Chemistry Reference
In-Depth Information
R = (CH
2
)
n
CH
3
have demonstrated the carbon number of substituent group,
n
, increases the rate constants up to
n
< 7, followed by no further increase at
n
≥ 7. Significantly, substituent group carbon number
n
had no affect on the
reaction of O
3
with the same alkenes. Steric and ring strain effects appear to
control the rate constants of the reactions of these alkenes with
•
OH,
NO
•
,
and O
3
[278].
NO
•
is a nighttime atmospheric oxidant and its reactivity with most organic
molecules is many orders of magnitude higher than of O
3
or
NO
•
[279]. Reac-
tion mechanisms of reactions of
NO
•
with molecules include electron transfer,
hydrogen abstraction, and addition to the π system [279]. The reaction between
NO
•
and
NO
•
can take place to yield N
2
O
5
in the absence of organic reactants,
and N
2
O
5
acts as a reservoir for
NO
•
[279]. Recently, the reactions of
NO
•
with
N
- and
C
-protected aromatic amino acids in the presence of O
2
, O
3
,
NO
•
, and
N
2
O
4
have been studied [280, 281]. Consistent with the chemistry of
NO
•
, the
initial electron transfer step at the aromatic ring occurred, followed by multi-
steps, which finally yield nitroaromatic compounds [280]. The formation of
products was not influenced by the presence of O
2
when reactions of
NO
•
with
tyrosine and phenylalanine were studied. In the case of tryptophan, an intra-
molecular oxidizing cyclization involving the amide moiety leads to the forma-
tion of tricyclic products. Results suggest
NO
•
may cause damage to the
peptides lining the respiratory tract, ultimately causing pollution-driven dis-
eases [281].
1.4.2 Disinfection By-Products (DBP)
Dissolved organic nitrogen (DON) in the aquatic environment is of interest
due to the bioavailability and connections between the carbon and nitrogen
biogeochemical cycles [282]. The concentrations of nitrogen-containing sub-
stances in aquatic environments have increased due to inputs from agricultural
runoff, deposition of NO
x
, and wastewater effluents [283-285]. Dissolved free
amino acids are one of the constituents of DON [286]. Amino acids have been
found in a number of water resources including drinking water, lakes, rivers,
marshes, and groundwaters [287-289]. Amino acids may also be found in
industrial effluents because of their many uses and applications. Proteins have
been detected in wastewater treatment effluents [290].
A number of disinfectants/oxidants are used in the treatment of water.
Redox potentials of oxidants are provided in Table 1.8 [291-294]. Under acidic
conditions, the redox potential of
•
OH is one of the highest of any oxidant
(Table 1.8). However, the potential is low under basic conditions. Under acidic
conditions, the order of redox potentials of oxidants without chlorine and
transition metal species are
•
−•
•
−•
OH SO
>
>
NO O H O CO
>
>
>
>
HSO O
>
4
3
3
2
2
3
5
2
2
. Redox potentials of some oxidants (
SO
−•
,
NO
•
,
CO
−•
, HSO
5
, ClO
2
, and Cl
2
)
have no pH dependence. Ozone has a high redox potential in alkaline medium.
Among the high-valent iron and manganese species, redox potentials of Fe(VI)
(Fe
6+
/Fe
3+
) and Mn(VI) (Mn
6+
/MnO
2
) are similar and higher than Mn(VII).
HSO O
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