- Biomimetic simazine oxidation catalyzed by metalloporphyrins
-
The metalloporphyrin-mediated simazine oxidation was investigated, in order to evaluate whether metalloporphyrins were good biomimetic models for the oxidation of this herbicide. The commercially available second-generation metalloporphyrins: 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin metal(III) chloride, [M(TDCPP)]Cl; 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin metal(III) chloride, [M(TFPP)]Cl; and 5,10,15,20-tetrakis(N-methyl-4-pyridyl) porphyrin metal(III) chloride, [M(TMPyP)]Cl5 (metal = Fe or Mn), and the oxidants iodosylbenzene (PhIO), hydrogen peroxide, and 3-chloroperoxy benzoic acid (m-CPBA) were employed in this study. Results demonstrated that these metalloporphyrins can mimic both the in vivo and in vitro action of cytochrome P450 for simazine oxidation, with formation of the dechlorinated metabolites OEET and OEAT mainly, as well as production of two other unknown compounds, identified by HPLC/mass spectrometry as ODET and ODDT. Among the systems, [Fe(TDCPP)]Cl/m-CPBA was the most efficient for simazine oxidation, giving up to 49% total conversion. Although hydrogen peroxide did not afford the best results (about 14% simazine conversion), it can be considered the most efficient oxidant from the point of view of toxicity, because it leads to less toxic products, namely OAAT and OEAT. The effect of some reaction conditions was investigated, and product evolution as a function of time was also monitored. Based on these results, simplified reaction mechanisms have been proposed.
- Santos, Joicy Santamalvina Dos,Palaretti, Vinícius,Faria, André Luiz De,Crevelin, Eduardo José,Moraes, Luiz Alberto Beraldo De,Assis, Marilda Das Dores
-
scheme or table
p. 163 - 170
(2012/05/04)
-
- Evaluation and Optimisation of the Reagent Addition Sequence during the Synthesis of Atrazine (6-Chloro-N2-ethyl-N4-isopropyl-1,3, 5-triazine-2,4-diamine) Using Reaction Calorimetry
-
The sequence of reagent addition and associated heats of reaction during the synthesis of the important herbicide atrazine (6-chloro-N 2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) from cyanuric chloride, isopropylamine, and ethylamine have been investigated by means of calorimetric and analytical methods. Sodium hydroxide was used as proton scavenger in this procedure. The best addition sequence found was the concurrent addition of amine and NaOH, keeping the amine in slight excess at all times. Using this feed sequence, the reaction becomes feed-controlled, and provided that a proper level of mixing can be maintained in the reactor, a high degree of control over reaction selectivity is obtained.
- Barton, Benita,Gouws, Shawn,Schaefer, Melissa C.,Zeelie, Bernard
-
p. 1071 - 1076
(2013/09/05)
-