Trapping of unstable conformations from thermal molecular beams in argon matrices: 1,2-difluoroethane and 1,3-butadiene, i.r. spectra and conformer equilibria

Huber-Wälchli, P.; Günthard, Hs. H.

doi:10.1016/0584-8539(81)80159-6

Cited by 117 publications

(63 citation statements)

References 26 publications

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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%

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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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Section: Conformation Preferencesupporting

confidence: 77%

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 magnitude of this preference (anti-gauche) has been calculated in the range of 0.5-1.0 kcal mol À1 [4,5]. This contra intuitive preference appears to originate from vicinal interactions possible between the polar C-F bond and other polar covalent bonds.…”

Section: Introductionmentioning

confidence: 97%

Solid state and theoretical evaluation of β-fluoroethyl esters indicate a fluorine-ester gauche effect

Briggs

O’Hagan

Rzepa

et al. 2004

Journal of Fluorine Chemistry

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“…Observing the vibrational spectrum of the high-energy rotational conformer of buta-1,3-diene (see for example, Panchenko et al [22]) were not successful until the 1978-1983 time frame [23][24][25][26]. The first scaled quantummechanical force field (SQM-FF) vibrational analysis of this molecule was performed by Panchenko et al [27].…”

Section: Introductionmentioning

confidence: 99%

“…The first scaled quantummechanical force field (SQM-FF) vibrational analysis of this molecule was performed by Panchenko et al [27]. The extraordinary experiments performed [23][24][25][26] initiated a series of SQM-FF vibrational analyses of this molecule at a variety of computational levels [28][29][30][31]. SQM-FF methodology [32][33][34] has been shown to be highly successful at predicting the wavenumbers of the high-energy conformer of buta-1,3-diene [29].…”

Section: Introductionmentioning

confidence: 99%

Identification of the high-energy conformer of octa-1,3,5,7-tetraene detected in the one-photon excitation fluorescence spectrum

et al. 2009

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Scaled quantum-mechanical force field (SQM-FF) vibrational analyses at the HF/6-31G//HF/6-31G computational level of the gauche, of octa-1,3,5,7-tetraene were used to identify the rotational isomer observed in the one-photon excitation fluorescence spectrum of this conjugated molecule (Ackerman et al. in J Chem Phys 80:39-44, 1984) as the gauche,Trans,trans, Trans,trans (gTtTt)-conformer. The analysis was performed by comparing the RMS deviations of the 14 fundamental wavenumbers assigned to the high-energy conformer of octa-1,3,5,7-tetraene in the fluorescence spectrum with those calculated for these conformers. Some reassignments of the wavenumbers, originally suggested by experimental observations, were required for the current analysis. The non-planar structure of gTtTt-octa-1,3,5,7-tetraene was calculated to have the terminal -CH=CH 2 moiety rotated by *30.5°with respect to the remainder of the nearly planar skeleton using both the HF/6-31G and MP2(FC)/aug-cc-pVDZ computational levels. The barriers to rotation of the -CH=CH 2 moiety at the MP2(FC)/augcc-pVDZ level were as follows: rotation from the lowestenergy planar all-trans conformer to the non-planar gTtTtconformer was 31.4 kJ/mol; rotation from the gTtTt-conformer to the planar all-trans conformer was 18.0 kJ/mol; and the barrier between the two equivalent gTtTt-octa-1,3,5,7-tetraene conformers was only 1.4 kJ/mol.Keywords Octa-1,3,5,7-tetraene Á Rotational isomerism Á Scaled quantum-mechanical force field Á Vibrational analysis Á HF/6-31G Á MP2(FC)/aug-cc-pVDZ

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Trapping of unstable conformations from thermal molecular beams in argon matrices: 1,2-difluoroethane and 1,3-butadiene, i.r. spectra and conformer equilibria

Cited by 117 publications

References 26 publications

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

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

Solid state and theoretical evaluation of β-fluoroethyl esters indicate a fluorine-ester gauche effect

Identification of the high-energy conformer of octa-1,3,5,7-tetraene detected in the one-photon excitation fluorescence spectrum

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