Computational characterization of the herbicide metolachlor and its mono-hydroxylated photodegradation products

Dublin Core

Título

Computational characterization of the herbicide metolachlor and its mono-hydroxylated photodegradation products

Tema

HERBICIDAS
FOTODEGRADACION
FOTODEGRADACION
BIBLIOGRAFIA NACIONAL QUIMICA
2018

Abstract

Electronic structure calculations have been performed for the characterization of the different conformers of the herbicide metolachlor (MC), (2-chloro-N-(2-methyl-6-ethylphenyl)-N-(2-methoxy-1-methylethyl) acetamide), the radical structures obtained through the photo chemical breaking of the C–Cl bond and the most important, experimentally identified mono-hydroxylated photo-fragmentation products. Only the S-metolachlor enantiomer that shows herbicide activity was studied. The goal of the study has been twofold. The first target has been the conformational analysis of the neutral molecule and the corresponding radical. Ten different conformers were identified for the S-metolachlor enantiomer, all of them exhibiting a near perpendicular disposition of the amidyl and the phenyl planes. They were classified into two families of minima depending on the orientation of the carbonyl group (either cis or trans with respect to the phenyl ring). All the minima in the S-cis family were found to lie higher than those in the S-trans family. The free energy of isomerization between the lowest minima of each family was found to be ΔG0298 = 6.2 kcal/mol, while the isomerization barrier around the amide C–N bond causing atropisomerism was calculated to be 34.9 kcal/mol (in good agreement with the experimental energy of activation, 36.9 ± 3 kcal/mol) [45]. The second part of the work is devoted to the computational characterization of the most important isomeric forms of the metolachlor radical and the major photodegradation mono-hydroxylated metabolites formed through the coupling of the metolachlor radical with OH. Reaction enthalpies and free energies for the various hydroxylation pathways have been calculated. Based on their order, the relative significance of the various hydroxylation channels is justified and the preference in the phenyl ring hydroxylation is established. The lowest exothermicity value determined, − 5.8 kcal/mol at the M06/6-31 + G(d,p) level, corresponds to phenyl group hydroxylation at the p-position with regard to C–N bond, in excellent agreement with the experimental findings.

Autor

Salta, Zoi
Kosmas, Agnie M.

Fuente

Theoretical Chemistry Accounts  v. 137, 2018. -- 12p.--e151

Editor

Springer

Fecha

2018

Derechos

Información sobre Derechos de Autor

(Por favor lea este aviso antes de abrir los documentos u objetos)

La legislación uruguaya protege el derecho de autor sobre toda creación literaria, científica o artística, tanto en lo que tiene que ver con sus derechos morales, como en lo referente a los derechos patrimoniales con sujeción a lo establecido por el derecho común y las siguientes leyes (LEY 9.739 DE 17 DE DICIEMBRE DE 1937 SOBRE PROPIEDAD LITERARIA Y ARTISTICA CON LAS MODIFICACIONES INTRODUCIDAS POR LA LEY DE DERECHO DE AUTOR Y DERECHOS CONEXOS No. 17.616 DE 10 DE ENERO DE 2003, LEY 17.805 DE 26 DE AGOSTO DE 2004, LEY 18.046 DE 24 DE OCTUBRE DE 2006)

ADVERTENCIA - La consulta de este documento queda condicionada a la aceptación de las siguientes condiciones de uso: Este documento es únicamente para usos privados enmarcados en actividades de investigación y docencia. No se autoriza su reproducción con fines de lucro. Esta reserva de derechos afecta tanto los datos del documento como a sus contenidos. En la utilización o cita de partes debe indicarse el nombre de la persona autora.

Formato

PDF

Idioma

Inglés

Tipo

Artículo

Identificador

DOI: 10.1007/s00214-018-2353-6

Document Item Type Metadata

Original Format

PDF
Fecha de agregación
March 22, 2019
Colección
Bibliografía Nacional Química
Tipo de Elemento
Document
Etiquetas
, ,
Citación
Salta, Zoi, “Computational characterization of the herbicide metolachlor and its mono-hydroxylated photodegradation products,” RIQUIM - Repositorio Institucional de la Facultad de Química - UdelaR, accessed August 21, 2019, http://riquim.fq.edu.uy/items/show/5649.
Archivos