Conformational and structural studies of 1-chloropropane and 1-bromopropane from temperature-dependant FT-IR spectra of rare gas solutions and ab initio calculations

Durig, J. R.; Zhu, Xiaodong; Shen, Shiyu

doi:10.1016/s0022-2860(01)00473-2

Cited by 45 publications

(27 citation statements)

References 33 publications

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“…39 It is well known that ab intio Hartree-Fock (HF) theoretical wavenumbers are ¾10% higher compared with experiments owing to the neglect of electron correlation. 40,41 In contrast, the ab initio Møller-Plesset second perturbation method (MP2) with full electron correlation provides good geometric parameters for hydrocarbons and halo-substituted hydrocarbons, 42,43 which minimize the percentage error. However, even correlated methods predict slightly higher force field constants, which can be improved by using scaling factors to be more compatible with the anharmonic experimental data 44,45 that depend on the level of calculations, basis sets and the weighing factor for each vibrational mode.…”

Section: Force Fields and Vibrational Wavenumbersmentioning

confidence: 99%

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Mohamed

Aly

2004

J Raman Spectroscopy

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Six conformers are proposed for the trans,trans-2,4-hexadiene (TTHD) molecule. Utilizing the 6-31G(d) and 6-311+G(d) basis sets at the levels of RHF, MP2 with full electron correlation and DFT-B3LYP, five conformers are found to be transition states, due to the calculated imaginary wavenumber(s). Accordingly, the totally symmetric TTT conformer where the two methyl groups are staggered to all trans vinylic hydrogen's (C 2h symmetry) is the stable conformer in the gaseous, liquid and crystalline phases. Aided by MP2(full)/6-311+G(d) geometric parameters, a chosen value of the kinetic parameter F = 6.11284856 was determined. Utilizing the observed band at 148 cm −1 in the far-infrared spectrum of the gas, a value of 1.41 ± 0.06 kcal mol −1 was obtained for the C 3v internal rotor (V 3 ), compared with 1.83 ± 0.07 kcal mol −1 predicted from a potential energy surface scan (1 kcal = 4.184 kJ). Aided by normal coordinate analysis and quantum chemistry (QC) calculations, the scaled quantum mechanical (SQM) force field was obtained employing five scaling factors for different types of vibrational motions. The scaled vibrational wavenumbers from both MP2(full) and B3LYP levels using the 6-31G(d) basis set provides an excellent approach to the observed fundamentals in either infrared or Raman spectra of the TTT conformer. Thus, confident vibrational assignments and potential energy distributions (PEDs) were provided for all fundamental modes of the TTT conformer. Moreover, the conformational stabilities, structural parameters, rotational constants, infrared intensities and Raman scattering activities are also reported. These results are discussed and compared with the experimentally determined values for some related conjugate systems when appropriate.

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Section: Force Fields and Vibrational Wavenumbersmentioning

confidence: 99%

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Mohamed

Aly

2004

J Raman Spectroscopy

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“…However, in n-propylfluoride, chloride, and bromide the gauche conformer had a somewhat lower enthalpy than the anti form. 3,4 We decided to include TFPS and the deuterated molecule TFPSD in this series of studies in order to investigate the effect of the SiH 3 moiety, compared to the bulky substituents SiF 3 and SiCl 3 on the conformational equilibrium. Moreover, we wanted to compare the SiH 3 and SiD 3 group wavenumbers in TFPS and TFPSD with those in n-propylsilane 7 and 2-chloroethylsilane, 8 and take into account the older vibrational studies of a number of alkylsilanes.…”

Section: Introductionmentioning

confidence: 99%

Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3‐trifluoropropyl‐ silane and 3,3,3‐trifluoropropylsilane‐d₃

Klæboe

Guirgis

Witkowski

et al. 2006

J Raman Spectroscopy

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were obtained in the vapour, liquid, and crystalline solid phases in the range 4000-50 cm −1 . Additional spectra in argon matrices at 5 K were recorded before and after annealing to temperatures 20-34 K. Raman spectra of the compounds as liquids were recorded at various temperatures between 296 and 183 K and spectra of the amorphous and crystalline solids were obtained.The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the two vapours were shock-frozen on a cold finger at 78 K, they turned partly crystalline immediately. After subsequent annealing to 140-150 K, ca 7-9 Raman bands of both molecules present in the liquids vanished in the crystal. Similar variations in intensity were observed in the corresponding infrared spectra before and after annealing. The spectra revealed the existence of one conformer (anti) in the crystal.From Raman intensity variations of three independent pairs of anti and gauche bands between 298 and 173 K for the parent compound, and 298 and 183 K for the deuterated analogue, the values 1 conf H o .gauche−anti/ = 4.1 ± 0.3 kJ mol −1 for the parent compound and the same value for the deuterated species were obtained in the liquid state. Annealing experiments in the matrices show that the gauche bands vanish after annealing, demonstrating that the anti conformer also has the lower energy here and that the barrier to gauche → anti inter-conversion is around 5-6 kJ mol −1 . The spectra of both conformers have been interpreted in detail.Ab initio and DFT calculations at the HF/6-311G**, B3LYP/6-311 G** and MP2/6-311 G** levels gave optimized geometries, infrared and Raman intensities and vibrational wavenumbers for the anti and gauche conformers. The conformational enthalpy difference derived from the calculations was between 6.0 and 4.1 kJ mol −1 with anti being the low energy conformer.

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“…1) being more stable. The corresponding enthalpy difference of 0.15±0.01 kcal/mol in liquid krypton has been reported in [9]. As the two conformers have similar dipole moments and molecular volumes, the latter result should be close to the value in the vapour state.…”

Section: Determination Of Calculation Resources and Evaluation Of Addmentioning

confidence: 59%

Quantum-mechanical evaluation of additivity increments for conformational energies: Chloroalkanes

Šatkovskienė

Pipiraite²,

Jankauskas³

et al. 2004

Lith. J. Phys.

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The ability of quantum-mechanical methods (HF/6-31G and MP2) to estimate additivity increments E XY G (X, Y = CH3, Cl), E XY GT , E XY GG , E XY GG ′ (X = Y = Cl) for conformational energies in chloro-substituted saturated hydrocarbons has been studied. Various basis sets including those extended by different sets of polarization functions both on heavy atoms (1d, 2d, 3d, 2d1f , 3d1f) and on hydrogens (1p, 2p, 3p) have been examined. The obtained results have been compared with available experimental data. It is shown that only the results obtained using the MP2 method and basis sets with polarization functions are in the scope with experimental estimates. The relative arrangement of conformational energies for various conformers in the series of polysubstituted chloroalkanes obtained using the additivity rule as well as direct quantum-mechanical calculations coincide with experimental findings. This fact can be considered as an argument that it is possibile to work out quantum-mechanically based additivity schemes for haloalkanes.

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Conformational and structural studies of 1-chloropropane and 1-bromopropane from temperature-dependant FT-IR spectra of rare gas solutions and ab initio calculations

Cited by 45 publications

References 33 publications

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3‐trifluoropropyl‐ silane and 3,3,3‐trifluoropropylsilane‐d₃

Quantum-mechanical evaluation of additivity increments for conformational energies: Chloroalkanes

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Conformational and structural studies of 1-chloropropane and 1-bromopropane from temperature-dependant FT-IR spectra of rare gas solutions and ab initio calculations

Cited by 45 publications

References 33 publications

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Vibrational analysis, conformational stability, force constants, barriers to internal rotations, RHF, MP2 and DFT calculations of trans,trans‐2,4‐hexadiene

Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3‐trifluoropropyl‐ silane and 3,3,3‐trifluoropropylsilane‐d3

Quantum-mechanical evaluation of additivity increments for conformational energies: Chloroalkanes

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Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3‐trifluoropropyl‐ silane and 3,3,3‐trifluoropropylsilane‐d₃