Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent

The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of 1J(C,H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH2 molecule was chosen as the primary model compound, in wh...

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Detalles Bibliográficos
Publicado: 2002
Materias:
Charge transfer
Chemical bonds
Dielectric materials
Electrons
Fermi level
Magnetic couplings
Nuclear magnetic resonance spectroscopy
Organic solvents
Anomeric effects
Molecular physics
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v100_n6_p705_Zaccari
http://hdl.handle.net/20.500.12110/paper_00268976_v100_n6_p705_Zaccari
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_00268976_v100_n6_p705_Zaccari2023-06-08T14:53:58Z Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent Charge transfer Chemical bonds Dielectric materials Electrons Fermi level Magnetic couplings Nuclear magnetic resonance spectroscopy Organic solvents Anomeric effects Molecular physics The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of 1J(C,H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH2 molecule was chosen as the primary model compound, in which both FC 1J(C,H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the 1J(C,H)FC couplings for C-H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: 'bond', 'direct lone pair' and the 'carbon-core orbitals'. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C-H) antibond (n(N)→(C-H)*) prior to the NJC dissection calculation. The dielectric solvation effect on both the total FC terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on 1J(C,H) couplings were estimated by evaluating molecular complex models of the form CH2=HN⋯S (S = H2O and DMSO). 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v100_n6_p705_Zaccari http://hdl.handle.net/20.500.12110/paper_00268976_v100_n6_p705_Zaccari
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Charge transfer
Chemical bonds
Dielectric materials
Electrons
Fermi level
Magnetic couplings
Nuclear magnetic resonance spectroscopy
Organic solvents
Anomeric effects
Molecular physics
spellingShingle Charge transfer
Chemical bonds
Dielectric materials
Electrons
Fermi level
Magnetic couplings
Nuclear magnetic resonance spectroscopy
Organic solvents
Anomeric effects
Molecular physics
Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
topic_facet Charge transfer
Chemical bonds
Dielectric materials
Electrons
Fermi level
Magnetic couplings
Nuclear magnetic resonance spectroscopy
Organic solvents
Anomeric effects
Molecular physics
description The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of 1J(C,H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH2 molecule was chosen as the primary model compound, in which both FC 1J(C,H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the 1J(C,H)FC couplings for C-H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: 'bond', 'direct lone pair' and the 'carbon-core orbitals'. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C-H) antibond (n(N)→(C-H)*) prior to the NJC dissection calculation. The dielectric solvation effect on both the total FC terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on 1J(C,H) couplings were estimated by evaluating molecular complex models of the form CH2=HN⋯S (S = H2O and DMSO).
title Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
title_short Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
title_full Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
title_fullStr Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
title_full_unstemmed Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1J(C,H) couplings and its dependence on solvent
title_sort natural j coupling (njc) analysis of the electron lone pair effect on nmr couplings: 2. the anomeric effects on 1j(c,h) couplings and its dependence on solvent
publishDate 2002
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v100_n6_p705_Zaccari
http://hdl.handle.net/20.500.12110/paper_00268976_v100_n6_p705_Zaccari
_version_ 1768546432795541504

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