Conformational and structural studies of 2,2-difluoroethylamine from temperature dependent infrared spectra of xenon solution and ab initio calculations

Durig, J. R.; Klaassen, Joshua J.; Panikar, Savitha S.; Darkhalil, Ikhlas D.; Ganguly, Arindam; Guirgis, Gamil A.

doi:10.1016/j.molstruc.2010.10.028

Cited by 9 publications

(5 citation statements)

References 25 publications

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“…The conformational isomerism of 2,2-difluoroethylamine ( 1 ) was computationally investigated at the MP2/6-311++g(d,p) level, both in the gas phase and implicit water (using the Polarizable Continuum Model). The conformational preferences are consistent with those obtained elsewhere through theoretical calculations and infrared spectroscopy [ 11 ]. No significant double gauche effect has been found in 1 , since conformers possessing two fluorine atoms in the gauche relationship with the amino group ( gauche-gauche , gg ) are estimated to be similarly populated to those conformers with only one single fluorine gauche to the nitrogen atom ( anti-gauche , ag ) ( Table 1 ).…”

Section: Resultssupporting

confidence: 90%

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

Silla¹,

Duarte²,

Cormanich³

et al. 2014

Beilstein J. Org. Chem.

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SummaryThe gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom in 2-fluoroethylamine hydrochloride on the conformational isomerism of the resulting 2,2-difluoroethylamine chloride (2). The analysis was carried out using NMR coupling constants in D2O solution, in order to mimic the equilibrium conditions in a physiological medium, in the gas phase and in implicit water through theoretical calculations. Despite the presence of σCH→σ*CF and σCH→σ*CN interactions, which usually rule the hyperconjugative gauche effect in 1,2-disubstituted ethanes, the most important forces leading to the double gauche effect (+NH3 in the gauche relationship with both fluorine atoms) in 2 are the Lewis-type ones. Particularly, electrostatic interactions are operative even in water solution, where they should be significantly attenuated, whereas hyperconjugation and hydrogen bond have secondary importance.

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Section: Resultssupporting

confidence: 90%

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

Silla¹,

Duarte²,

Cormanich³

et al. 2014

Beilstein J. Org. Chem.

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“…A number of studies on the relationship between the MIR absorption intensity and molecular structure as well as intramolecular charge distribution were carried out by Galabov et al − As a result of the development of quantum chemical calculations, one can satisfactorily reproduce the relation between molecular structure, frequencies, and absorption intensities of vibrational modes. − Molecular vibration analysis based on the harmonic oscillator model cannot reproduce experimental data with sufficient precision. The reason why quantum chemical calculations considering anharmonicity have not yet been explored intensively results from enormous amount of calculations required.…”

Section: Nir Spectroscopy and Quantum Chemical Calculation Studies Of...mentioning

confidence: 99%

Advances in Molecular Structure and Interaction Studies Using Near-Infrared Spectroscopy

et al. 2015

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“…Recently, we have been investigating the conformation stability and determined the structural parameters of several organoamines and alcohols . One of the first amines studies was ethylamine, which was determined to have the trans conformer more stable by 54 ± 4 cm –1 (0.65 ± 0.05 kJ/mol) than the gauche form.…”

Section: Introductionmentioning

confidence: 99%

Conformational and structural studies of n‐propylamine from temperature dependent Raman and far infrared spectra of xenon solutions and ab initio calculations

Durig

Darkhalil

Klaassen

et al. 2012

J Raman Spectroscopy

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The Raman and infrared spectra (4000 to 50 cm–1) of the gas, liquid or solution, and solid have been recorded of n‐propylamine, CH3CH2CH2NH2. Variable temperature (−60 to −100 °C) studies of the Raman (1175 to 625 cm–1) and far infrared (600 to 10 cm–1) spectra dissolved in liquid xenon were carried out. From these data, the five possible conformers were identified and their relative stabilities obtained with enthalpy difference relative to trans–trans (Tt) for trans–gauche (Tg) of 79 ± 9 cm–1 (0.9 ± 0.1 kJ/mol); for Gg of 91 ± 26 cm–1 (1.08 ± 0.3 kJ/mol); for Gg′ of 135 ± 21 cm–1 (1.61 ± 0.2 kJ/mol); for Gt of 143 ± 11 cm–1 (1.71 ± 0.1 kJ/mol). The percentage of the five conformers is estimated to be 18% for the Tt, 24 ± 1% for Tg, 23 ± 3% for Gg, 18 ± 1% for Gg′ and 18 ± 1% for Gt at ambient temperature. The conformational stabilities have been predicted from ab initio calculations utilizing several different basis sets up to aug‐cc‐pVTZ from both second‐order Møller–Plesset (MP2, full) and density functional theory calculations by the Becke, three‐parameter, Lee–Yang–Parr method. Vibrational assignments were provided for the observed bands for all five conformers, which are supported by MP2(full)/6‐31G(d) ab initio calculations to predict harmonic force constants, wavenumbers, infrared intensities, Raman activities and depolarization ratios for both conformers. Estimated r0 structural parameters were obtained from adjusted MP2(full)/6‐311+G(d,p) calculations. The results are discussed and compared with the corresponding properties of some related molecules. Copyright © 2012 John Wiley & Sons, Ltd.

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Conformational and structural studies of 2,2-difluoroethylamine from temperature dependent infrared spectra of xenon solution and ab initio calculations

Cited by 9 publications

References 25 publications

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

Advances in Molecular Structure and Interaction Studies Using Near-Infrared Spectroscopy

Conformational and structural studies of n‐propylamine from temperature dependent Raman and far infrared spectra of xenon solutions and ab initio calculations

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