170
J.S.d. Santos et al. / Applied Catalysis A: General 408 (2011) 163–170
FeIV(O)P is the first catalytic species observed in reactions using
[Fe(TFPP)]Cl, as indicated by the change in the color of the reaction
medium, from brown to orange concomitant to the changes in the
UV–vis spectrum showing a red-shifted Soret band (from 408 to
412 nm) and the appearance of a new band at 540 nm [37].
The hydroxyl amine products OEAT and OAAT are only obtained
when peroxides are the oxidant, indicating that these species could
be also generated from hydroperoxide intermediates.
[Fe(TMPyP)]Cl5 gave the lowest yields, probably due to their mod-
est electrophilicity. m-CPBA was the best oxidant, although H2O2
can be considered the most efficient because it leads to the for-
mation of dechlorinated products OAAT and OEAT, considered to
be the least toxic compounds. Results indicate that MePs can be
considered good biomimetic cytochrome P450 models for the oxi-
dation of this herbicide, and can be useful for the elucidation of the
in vivo simazine oxidation mechanism.
In our previous studies on atrazine (CEIT) oxidation catalyzed by
MePs, there was only one metabolite in common with the present
study: CEAT [15]. Although the other products from atrazine oxi-
dation were different, they have in common with the products
achieved in the present work, the formation of a carboxyamide
(ODDT and ODET for CEET and COA for CEIT). The hydroxylated
products predominate in simazine oxidation, while chlorinated
products are formed in atrazine oxidation. The steric hindrance of
the atrazine propyl side chain seems to be determinant for inter-
action with the catalytic center and is probably responsible for its
different reactivity compared with simazine.
Acknowledgment
We thank FAPESP, CNPq, and CAPES for financial support.
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The metalloporphyrins used in this study have been demon-
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account that this herbicide is highly persistent. Oxidation reactions
preferentially lead to dehalogenation, although one chlorinated
product is also observed in some conditions. Most of the reac-
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