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A theoretical study of the HCHO+CCl2 reaction: Cycloaddition or ylide formation? (1997)

Pliego, Jr., Josefredo R. ; De Almeida, Wagner B.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 106 (1997), S. 3582-3586

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The chemical reaction between HCHO and CCl2 was studied using a high level of theory. Geometry optimizations were performed at the complete active space self-consistent field (CASSCF) level with the 6-31G* basis set, and single point calculations were performed using the coupled-cluster with single, double, and perturbative inclusion of triple excitation [CCSD(T)] method. Additivity approximation of the correlation energy was used, so we have obtained an effective CCSD(T)/6-311G(2d1f,2p) reaction and activation energies. Our results show that the ylide exist as a stable species, having a transient character. Its lifetime in relation to ring closure was estimated to be 1 ms at 298.15 K, and it can react backward forming the HCHO and CCl2 fragments. The cycloaddition reaction is highly competitive with ylide formation, and that is the dominant process. The reaction rate of cycloaddition is about two and a half times higher than the ylide formation at 298.15 K. © 1997 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.473454

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Ab initio MP2 study of the HF …ClF complex using various extended basis sets and bond functions (1996)

Pliego Jr., Josefredo R. ; Resende, Stella M. ; Almeida, Wagner B. De

Springer

Theoretica chimica acta 93 (1996), S. 333-342

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ISSN: 0040-5744

Keywords: Key words: van der Waals complex ; Transition states ; Extended basis sets ; Bond functions ; Electronic correlation

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Summary. The stationary points on the intermolecular potential energy surface (PES) for the HF…ClF complex have been investigated at the second-order Møller–Plesset perturbation theory (MP2) level using various extended bais sets, including diffuse functions, and also bond functions. The last ones were placed at different intermolecular positions, for distinct stationary points. The basis set superposition errors (BSSE) were accounted for using the counterpoise method. Besides the anti-H-bonded and H-bonded minimum energy structures, four transition state structures were also located on the PES. It was shown that higher polarization functions are required for the description of the anti H-bonded isomer and diffuse functions had to be included for the H-bonded isomer. The bond functions are able to replace the f (Cl, F) and d(H) polarization functions at a lower computational cost. However, for the H-bonded isomer intramolecular electron correlation also plays an important role. So we have to use diffuse nucleus centered polarization functions for an adequate description of intermolecular and intramolecular correlation.