Direct dynamics calculations of deuterium and carbon-13 kinetic isotope effects for the reaction Cl+CH4.

CARBONO 13

BIBLIOGRAFIA NACIONAL QUIMICA

1998

The kinetic isotope effects, KIEs, for hydrogen abstraction from the isotopologs CH4, 13CH4, CH3D, and CD4 by chlorine atoms have been studied by the dual-level direct dynamics approach with the MORATE computer program. Low-level calculations of the potential energy surface were carried out at the NDDO-SRP level (in particular the AM1-SRP level), using two different sets of specific reaction parameters labeled SRP4 and SRP13. High-level structural and energetic properties of the reactants, saddle point, and products were obtained at the MP2-SAC and MP2 levels using the 6-311G(2d,d,p) basis set and were used to interpolate corrections to the low-level calculations. The dual-level calculations were carried out using the ICL-Eckart improved interpolated corrections algorithm. Tunneling was included by the microcanonical optimized multidimensional tunneling (μOMT) method, and we find that large-curvature tunneling paths usually provide the dominant contribution, with significant participation of excited vibrational states. Both rectilinear and curvilinear coordinates were applied to the unsubstituted reaction. The 12C/13C KIEs calculated at the MP2-SAC///SRP4 level using MP2 frequencies are in very close agreement with the experimental ones, with values of 1.07 and 1.06 at 243 and 297 K, respectively, as compared to experimental values of 1.07 at both temperatures. For the reaction CH3D + Cl, the calculated H/D KIEs are equal to 1.55 and 1.45 at 223 and 296 K, while the measured values are equal to 1.59 and 1.50, respectively. The H/D KIE for the reaction CD4 + Cl is calculated to decrease from 11 to 4.7 as the temperature increases from 300 K to 450 K, whereas the experimental value decreases from 12 to 3.9. We also make comparison with previous results for the unsubstituted reaction CH4 + Cl.

Journal of Physical Chemistry A v. 102, no. 24, 1998. -- p. 4568-4578

ACS

1998

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 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.

PDF

Inglés

Artículo

DOI: 10.1021/jp980759l

PDF