Rapid quantification of residual glyphosate in water treated with layered double hydroxides using liquid chromatography / Quantificação rápida de glifosato residual em água tratada com hidróxidos duplos lamelares usando cromatografia líquida

High performance liquid chromatography and an optimized colorimetric method were applied to determine the residual glyphosate in waters treated with double lamellar hydroxides such as MgxAlyCO3.nH2O. The chromatographic determination was by means of derivatization with 9-fluorenylmethylchloroformiate and running time less than 2 minutes, faster than analogous methods in the literature. The colorimetric method was performed by optimizing the Ruhemann purple method. The chromatographic and colorimetric methods presented LOQ of 1.05 and 2.08 ?g / mL and LOD of 0.31 and 0.84 ?g / mL, respectively. The percentages of recovery of the methods are between 93 to 105% with RSD less than 2.35% for the chromatographic method and 6% for the colorimetric. Both methods depend on the temperature. The double hydroxide Mg1Al1CO3.nH2O has the highest percentage of charge density (5.54 nm2) and the best performance in removing glyphosate from the aqueous medium

Theoretical calculations of the kinetics of the oh reaction with 2-methyl-2-propen-1-ol and its alkene analogue

In this work, the first and rate determining steps on the mechanism of the OH addition to 2-methyl-2-propen-1-ol (MPO221) and methylpropene (M2) have been studied at the DFT level, employing the BHandHLYP functional and the cc-pVDZ and aug-cc-pVDZ basis sets. The thermochemical properties of equilibrium (enthalpy, entropy and Gibbs free energies) have been determined within the conventional statistical thermodynamics relations and the rate coefficients have been determined on the basis of the variational transition state theory. The adoption of the microcanonical variational transition state theory was proved to be crucial for the description of the kinetics of OH addition to these unsaturated compounds. The rate coefficients obtained for the OH reactions with MPO221 and M2 at 298.15K deviate, respectively, 27% and 13% from the experimental rate coefficient available in the literature. A non-Arrhenius profile is observed for the rate coefficients. Moreover, the values of the rate coefficients for the MPO221 + OH reaction are greater than those for the M2 + OH reaction, suggesting that the substitution of the hydrogen atom in an alkene by the ?OH functional group, increases the reactivity in respect to the hydroxyl radical.Fil: Da Silva Barbosa, Thais. Departamento de Físico-química, Instituto de Química; BrasilFil: Nieto, Jorge Daniel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Cometto, Pablo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Lane, Silvia Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Bauerfeldt, Glauco Favilla. Universidade Federal Rural Do Rio de Janeiro; Brasil. Departamento de Química, Instituto de Ciencias Exatas; Brasi

Avaliação teórica e experimental da atividade anticorrosiva de enaminoésteres frente ao aço-carbono em meio ácido/ Theoretical and experimental evaluation of the anticorrosive activity of enaminoesters against carbon steel in acid medium

Corrosão pode ser definida como a deterioração de materiais, geralmente metálicos, por ação física, química ou eletroquímica do meio. Dentre os diversos materiais que podem sofrer corrosão, o aço carbono é o mais utilizado na indústria. Enaminoésteres são compostos considerados potenciais inibidores de corrosão devido a presença de grupos acila, amino e ligação dupla. Neste trabalho, três enaminoésteres foram sintetizados, derivados da anilina, benzilamina e fenetilamina, e sua atividade anticorrosiva avaliada através de experimentos eletroquímicos: Polarização Potenciodinâmica (PP), Resistência à Polarização Linear (RPL) e Espectroscopia de Impedância Eletroquímica (EIE). Cálculos teóricos foram utilizados para calcular a energia do orbital de fronteira HOMO (EHOMO), LUMO (ELUMO), a diferença de energia entre os orbitais (?ELUMO-HOMO) e momento de dipolo (µ). O derivado da fenetilamina apresentou melhor eficiência de inibição da corrosão com 90 e 92% pelas técnicas de EIE e RPL, respectivamente, correlacionado com o estudo de modelagem molecular que mostrou o menor valor de ?ELUMO-HOMO e maior momento de dipolo

Comparative kinetics of the 3-Buten-1-ol and 1-Butene reactions with OH radicals: a density functional theory/RRKM investigation

The compared kinetics of the reactions of unsaturated alcohols and alkenes with OH radicals is a topic of great interest from both the theoretical chemistry and the atmospheric chemistry points of view. The enhanced reactivity of an unsaturated alcohol, with respect to its alkene analogue, toward OH radicals has been previously demonstrated, at 298 K, by experimental and theoretical research. In this work, a new comparative investigation of such reactions is performed for 3-buten-1-ol and 1-butene. The model assumes that the overall kinetics is governed by the first OH addition steps of the mechanism. Calculations have been performed at the DFT level, employing the BHandHLYP functional and the cc-pVDZ and aug-cc-pVDZ basis sets, and the rate coefficients have been determined on the basis of the microcanonical variational transition state theory. The rate coefficients obtained for the OH reactions with 3-buten-1-ol (kOH31BO) and 1-butene (kOH1B) at 298.15 K are lower than the experimental rate coefficient available in the literature, showing deviations of 18% and 25%, respectively. Negative temperature dependence is verified for these rate coefficients. The kOH31BO/kOH1B ratios have also been investigated as a function of the temperature, suggesting that at room temperature the unsaturated alcohol reacts with the OH radicals faster than 1-butene, by a factor of 1.2, but at higher temperatures (400–500 K), the alkene should react faster, and that the stabilization of prebarrier complexes and saddle points due to hydrogen bonds is no longer an important factor to govern the reactivity of the unsaturated alcohol toward OH radicals, with respect to the alkene analogue.Fil: Peirone, Silvina Anahí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Nacional de Córdoba. Rectorado. Centro Laser de Ciencias Moleculares; ArgentinaFil: Nieto, Jorge Daniel. Universidad Nacional de Córdoba. Rectorado. Centro Laser de Ciencias Moleculares; ArgentinaFil: Cometto, Pablo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones y Transferencia de Villa María. Universidad Nacional de Villa María. Centro de Investigaciones y Transferencia de Villa María; ArgentinaFil: Barbosa, Thaís da Silva. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Bauerfeldt, Glauco Favilla. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Arbilla, Graciela. Universidade Federal do Rio de Janeiro; BrasilFil: Lane, Silvia Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin