Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH
Equations for the intramolecular surfaces of the 3HH coupling constants in ethane, ethylene, and acetylene are formulated, and the corresponding coefficients are estimated from calculations at the DFT/B3LYP level. The chosen variables are changes in bond lengths, in the torsion angle Pdbl between th...
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2014
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v112_n16_p2138_Diez http://hdl.handle.net/20.500.12110/paper_00268976_v112_n16_p2138_Diez |
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paper:paper_00268976_v112_n16_p2138_Diez2023-06-08T14:54:00Z Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH DFT/B3LYP extended Karplus equations intramolecular surfaces vibrational contributions vicinal coupling constants Acetylene Couplings Ethane Ethylene Fourier series Geometry Lighting Torsional stress DFT/B3LYP Equilibrium geometries Karplus equation Nuclear coordinates Proton-proton coupling constants Truncated Fourier series Vibrational contributions Vicinal coupling constants Protons Equations for the intramolecular surfaces of the 3HH coupling constants in ethane, ethylene, and acetylene are formulated, and the corresponding coefficients are estimated from calculations at the DFT/B3LYP level. The chosen variables are changes in bond lengths, in the torsion angle Pdbl between the coupled protons Ha and Hb, in bond angles, and in dihedral angles. The 3HH surface of ethane is formulated as an extended Karplus equation with the coefficients of a truncated Fourier series on the torsion angle Pdbl expanded as second-order Taylor series in the chosen variables taking into account the invariance of 3HH under reflections and rotations of nuclear coordinates. Partial vibrational contributions from linear and square terms corresponding to changes in the geometry of the Ha - Ca - Cb - Hb fragment are important while those from cross terms are small with a few exceptions. The 3HH surface of ethane is useful to predict contributions to 3HH from changes in local geometry of derivatives but vibrational contributions are predicted less satisfactorily. The predicted values at the B3LYP/BS2 level of the 3HH couplings (vibrational contributions at 300 K) from equilibrium geometries are 9.79 (-0.17) for acetylene, and 17.08 (1.93) and 10.73(0.93) for the trans and cis couplings of ethylene. © 2014 Taylor & Francis. 2014 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v112_n16_p2138_Diez http://hdl.handle.net/20.500.12110/paper_00268976_v112_n16_p2138_Diez |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
DFT/B3LYP extended Karplus equations intramolecular surfaces vibrational contributions vicinal coupling constants Acetylene Couplings Ethane Ethylene Fourier series Geometry Lighting Torsional stress DFT/B3LYP Equilibrium geometries Karplus equation Nuclear coordinates Proton-proton coupling constants Truncated Fourier series Vibrational contributions Vicinal coupling constants Protons |
| spellingShingle |
DFT/B3LYP extended Karplus equations intramolecular surfaces vibrational contributions vicinal coupling constants Acetylene Couplings Ethane Ethylene Fourier series Geometry Lighting Torsional stress DFT/B3LYP Equilibrium geometries Karplus equation Nuclear coordinates Proton-proton coupling constants Truncated Fourier series Vibrational contributions Vicinal coupling constants Protons Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| topic_facet |
DFT/B3LYP extended Karplus equations intramolecular surfaces vibrational contributions vicinal coupling constants Acetylene Couplings Ethane Ethylene Fourier series Geometry Lighting Torsional stress DFT/B3LYP Equilibrium geometries Karplus equation Nuclear coordinates Proton-proton coupling constants Truncated Fourier series Vibrational contributions Vicinal coupling constants Protons |
| description |
Equations for the intramolecular surfaces of the 3HH coupling constants in ethane, ethylene, and acetylene are formulated, and the corresponding coefficients are estimated from calculations at the DFT/B3LYP level. The chosen variables are changes in bond lengths, in the torsion angle Pdbl between the coupled protons Ha and Hb, in bond angles, and in dihedral angles. The 3HH surface of ethane is formulated as an extended Karplus equation with the coefficients of a truncated Fourier series on the torsion angle Pdbl expanded as second-order Taylor series in the chosen variables taking into account the invariance of 3HH under reflections and rotations of nuclear coordinates. Partial vibrational contributions from linear and square terms corresponding to changes in the geometry of the Ha - Ca - Cb - Hb fragment are important while those from cross terms are small with a few exceptions. The 3HH surface of ethane is useful to predict contributions to 3HH from changes in local geometry of derivatives but vibrational contributions are predicted less satisfactorily. The predicted values at the B3LYP/BS2 level of the 3HH couplings (vibrational contributions at 300 K) from equilibrium geometries are 9.79 (-0.17) for acetylene, and 17.08 (1.93) and 10.73(0.93) for the trans and cis couplings of ethylene. © 2014 Taylor & Francis. |
| title |
Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| title_short |
Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| title_full |
Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| title_fullStr |
Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| title_full_unstemmed |
Intramolecular surfaces for vicinal proton-proton coupling constants 3 J HH |
| title_sort |
intramolecular surfaces for vicinal proton-proton coupling constants 3 j hh |
| publishDate |
2014 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v112_n16_p2138_Diez http://hdl.handle.net/20.500.12110/paper_00268976_v112_n16_p2138_Diez |
| _version_ |
1768542876615049216 |