Gas-phase 19F and 1H high-resolution n.m.r. spectroscopy: application to the study of unperturbed conformational energies of 1,2-difluoroethane

Hirano, Tsuneo; Nonoyama, Shinji; Miyajima, Takashi; Kurita, Yasuyuki; Kawamura, Tokiji; Sato, Hisaya

doi:10.1039/c39860000606

Cited by 36 publications

(23 citation statements)

References 1 publication

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“…Higher level calculations at the Gaussian-2 (G2>@ level of theory predict a similar energy difference of 0.76 kcal/mol. These theoretical estimates are in pleasing agreement with the experimental value of 0.59 kcal mol, obtained via infrared spectroscopyP9 as well as the I9F NMR estimate, 47 (Table V).…”

Section: Application Of V To Scrf Calculationssupporting

confidence: 87%

Ab initiocalculation of molar volumes: Comparison with experiment and use in solvation models

1995

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A simple and efficient procedure of calculating molecular volume (V,) based on the Monte Carlo method is presented. The volume of a molecule is defined by the volume occupied by the 0.001-au electron density envelope. We have employed this method to compute the molecular volumes (V, ) of a large selection of organic molecules and compare them with the corresponding molar volumes (V,) measured in the liquid state. A strong correlation is found to exist between the V, and V, values (V,/V, = 0.75). Using this linear relationship, the calculated molecular volume may provide an estimate of the cavity-volume parameter in solvent-effect calculations. As a chemical application of molecular volume, we have investigated the conformational equilibrium of 1,2difluoroethane in the liquid state using the self-consistent reaction field theory.

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Section: Application Of V To Scrf Calculationssupporting

confidence: 87%

Ab initiocalculation of molar volumes: Comparison with experiment and use in solvation models

1995

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“…The differences between the two methods are within the error range of CBS-QB3 as shown by tests on the G2 group of compounds [33]. It should be noted that the calculated DG gauche-anti values by the CBS-QB3 method for compounds 1 and 2 are in excellent agreement with the reported experimental data [1][2][3][4][5][6][7][8][9].…”

Section: Conformation Preferencesupporting

confidence: 77%

“…The structures and rotational barriers about the C-C bonds of 1,2-difluoroethane (1) and 1,2-dichloroethane (2) have been investigated experimentally [1][2][3][4][5][6][7][8][9][10][11] and theoretically [11][12][13]. Haloethanes are an alternative to chlorofluorocabons, CFCs, believed to be major contributors to the seasonal ozone depletion over the Antarctic continent [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Complete basis set, hybrid-DFT study, and NBO interpretations of the conformational behavior of 1,2-dihaloethanes

Nori‐Shargh

Boggs

2010

Struct Chem

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The conformational behavior of 1,2-difluoroethane (1), 1,2-dichloroethane (2), 1,2-dibromoethane (3), and 1,2-diiodoethane (4) have been analyzed by means of complete basis set CBS-QB3, hybrid-density functional theory (B3LYP/Def2-TZVPP) based methods and natural bond orbital (NBO) interpretation. Both methods showed the expected greater stability of the gauche conformation of compound 1 compared to its anti conformation. Contrary to compound 1, the anti conformations of compounds 2-4 are more stable than their gauche conformation. The stability of the anti conformation compared to the gauche conformation increases from compound 1 to compound 4. The NBO analysis of donor-acceptor (r ? r*) interactions showed that the generalized anomeric effect (GAE) is in favor of the gauche conformation of compound 1. Contrary to compound 1, GAE is in favor of the anti conformations of compounds 2-4. The GAE values calculated (i.e., GAE anti -GAE gauche ) increase from compound 1 to compound 4. On the other hand, the calculated dipole moment values for the gauche conformations decrease from compound 1 to compound 4. In the conflict between the GAE and dipole moments, the former succeeded in accounting for the increase of the anti conformation stability from compound 1 to compound 4. There is a direct correlation between the calculated GAE,The correlations between the GAE, bond orders, total steric exchange energies (TSEEs), DG Anti-Gauche , DG à (Gauche ? Gauche 0 , C 2v ), DG à (Anti ? Gauche, C 2 ), dipole-dipole interactions, structural parameters, and conformational behaviors of compounds 1-4 have been investigated.

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“…A recent gas phase NMR study estimated the 1,2-difluoroethane value to be about 0.8 kcal/mol in favor of the gauche conformation. 61 The fairly consistent experimental values of the 1,1,2-trifluoro-and 1,1,2,2-tetrafluoroethanes are not reproduced by the same set of torsional F-C -C -F constants as for the vicinal difluoro compounds, neither by MM2 nor by MMBIPEOE. This difficulty has been realized by Meyer who introduced a different set of torsional constants for this torsion, when fluorine was geminal to another fluorine a t~m .~,~' Abraham and Stglevik also noted a discrepancy in conformational energy of 1.6 kcal/mol in 1,2-difluoroethane compared to experiment, when they used steric F-F potentials derived from the other fluoroalkanes studied.'…”

Section: -C Yclohexanesmentioning

confidence: 86%

Electrostatic interactions in molecular mechanics (MM2) calculations via PEOE partial charges I. Haloalkanes

1988

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The PEOE (partial equalization of orbital electronegativity) procedure has been modified slightly and reparametrized for haloalkanes to calculate partial atomic charges suitable for evaluation of dipole moments and electrostatic energies in conjunction with molecular mechanics (MM2) calculations. Dipole moments of 66 haloalkanes are calculated with an average absolute deviation of 0.14 D from experimental values. The conformational energies of 40 compounds have been calculated and the agreement with experimental data is generally good and compares well with calculations by the IDME (induced dipole moment and energy) method. In addition, carbon and proton charges correlate well with C-1s core binding energies and 'H-NMR (nuclear magnetic resonance) shifts for halomethanes. The most striking benefit of treating electrostatics through a set of partial charges compared to the standard MM2 bond dipole approach is demonstrated by calculations on 1,4-disubstituted cyclohexanes, for which standard MM2 fails to predict the most stable conformation.

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Gas-phase 19F and 1H high-resolution n.m.r. spectroscopy: application to the study of unperturbed conformational energies of 1,2-difluoroethane

Cited by 36 publications

References 1 publication

Ab initiocalculation of molar volumes: Comparison with experiment and use in solvation models

Ab initiocalculation of molar volumes: Comparison with experiment and use in solvation models

Complete basis set, hybrid-DFT study, and NBO interpretations of the conformational behavior of 1,2-dihaloethanes

Electrostatic interactions in molecular mechanics (MM2) calculations via PEOE partial charges I. Haloalkanes

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