Vicinal NMR proton - Proton coupling constants. An NBO analysis

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A method of natural bond orbital (NBO) interactions between bonds and antibonds, σm → σn*, has been developed for analyzing vicinal proton - proton coupling constants, 3JHH. The contribution to 3JHH from such an interaction σm → σn* is defined as Jmn* and is obtained following these three steps: (i)...

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Detalles Bibliográficos
Autores principales: Esteban, A.L., Galache, M.P., Mora, F., Díez, E., Casanueva, J., San Fabián, J., Barone, V., Peralta, J.E., Contreras, R.H.
Formato: JOUR
Materias:
Proton-proton coupling constants
Chemical bonds
Fluorine
Hydrogen
Nuclear magnetic resonance
Paraffins
Protons
Molecular dynamics
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_10895639_v105_n21_p5298_Esteban
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:A method of natural bond orbital (NBO) interactions between bonds and antibonds, σm → σn*, has been developed for analyzing vicinal proton - proton coupling constants, 3JHH. The contribution to 3JHH from such an interaction σm → σn* is defined as Jmn* and is obtained following these three steps: (i) the SOS scheme is used to calculate 3JHH; (ii) the same calculation is repeated after deleting the relevant off-diagonal elements in the NBO Fock matrix; (iii) Jmn* is obtained as the difference between those calculated in steps i and ii. Application of this method to the ethane and fluoroethane molecules shows that the main contribution to 3JHH comes from the through space term while the substitution of a hydrogen in ethane by a fluorine changes this through space term and, in addition, gives a direct contribution to 3JHH. © 2001 American Chemical Society.

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