Infrared cryogenic studies

Barnes, Austin J.; Evans, Mark; Hallam, H. E.

doi:10.1016/0022-2860(83)90026-1

Cited by 12 publications

(7 citation statements)

References 16 publications

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“…17 Condensation of 2 chlorobutane leads to three conformers, which manifests itself as splitting of some bands in the IR spec tra into three components similarly to the case of liquid and argon isolated 2 ClBu. 18, 19 The conformer ratio, with predomi nant contribution of one of them, remains almost unchanged with an increase in temperature.…”

Section: Methodsmentioning

confidence: 90%

“…The classi cal planar carbocation structure (B) and the s Bu + struc ture with symmetric hydrogen bridge (C) have similar energies but are less energetically favorable (however, the energy difference is less than 1 kcal mol -1 ). Analogous (24) 1415 (18) 1412 (17) 1409 (24) 1370 (6) 1409 (7) 1394 (9) 1359 (19) 1351 (8) Note: A is the structure with methyl bridge, B is the classical planar structure, and C is the structure with hydrogen bridge. * Band intensities are given in parentheses.…”

Section: The Structure Of Sec Butyl Cationmentioning

confidence: 96%

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Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

et al. 2005

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Sec butyl and tert butyl cations were first stabilized upon cocondensation of aluminum chloride and haloalkanes (2 chlorobutane and 2 chloro 2 methylpropane, respectively) and their IR spectra and thermal stability investigated. Aluminum chloride anions participating in stabilization of carbenium ions were revealed. Ionic complexes and both 1:1 and 2:1 molecular complexes of reagents were detected and their IR spectra studied. Quantum chemical calcula tions at the PBE level of density functional theory with inclusion of electron correlation were employed to optimize the geometric parameters and to determine the vibrational frequencies of aluminum chloride, butyl chlorides, and their complexes of various compositions. The struc tures of the associates observed were determined on the basis of comparison of the experimental and calculated vibrational spectra.

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Section: Methodsmentioning

confidence: 90%

Section: The Structure Of Sec Butyl Cationmentioning

confidence: 96%

Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

et al. 2005

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“…Including the experimental uncertainty of the third value indicates that the anti conformer is slightly preferred over the gauche conformer by about 0.1 kcal/mol. Other experiments give E rel values as −0.25 kcal/mol,16 −0.36 ± 0.03 kcal/mol,9 and −0.47 ± 0.30 kcal/mol 9. In the opinion of the authors, the latter three experimental values are overestimated.…”

Section: Resultsmentioning

confidence: 78%

“…However, some of the done experiments on the conformations of 1‐chloropropane13–15 and of 1‐bromopropane15 indicate that the G and the A conformers are approximately of the same stability in both compounds. Other experiments show that G conformer is more stable than A in both 1‐chloropropane9, 16 and 1‐bromopropane 9, 13. Consequently, the second purpose of the present work is doing ab initio investigations on the relative stabilities of the gauche conformers of 1‐fluoro‐, 1‐chloro‐, and 1‐bromopropanes.…”

Section: Introductionmentioning

confidence: 92%

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C₃H₇X where X = F, Cl, and Br

2002

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HF, MP2, and B3LYP calculations with different basis sets have been used in the computation of the stabilization energies of C(3)H(7)X isomers, where X is F, Cl, and Br. The experimental stabilization energies of the structural isomers of C(3)H(7)Cl and C(3)H(7)Br have been reproduced via B3LYP calculations. However, the calculated stabilization energies of fluoropropane isomers from their reported enthalpies of formation have been reproduced in all methods of calculations in present work. The experimental relative stabilities of the gauche conformers of 1-fluoro-, 1-chloro-, and 1-bromopropanes have been also reproduced via some of the used calculations in the present work. The effect of the geminal interactions on X atomic charges and on the C-X and C-C bond lengths in halopropane isomers are also discussed.

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“…In the present study, we show that matrix effects are not systematic, thus, not easily transferrable from one case to another. This investigation comprises widely studied MI-IR spectra of the monomeric species of water [3][4][5][6][7][8][9][10][11], carbon dioxide [12][13][14][15][16], methane [17][18][19][20][21][22][23], and methanol [24][25][26][27][28]. We refer to further in-depth historical accounts for water [29] as well as carbon dioxide and methane [30].…”

Section: Introductionmentioning

confidence: 99%

On the synergy of matrix-isolation infrared spectroscopy and vibrational configuration interaction computations

et al. 2020

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The key feature of matrix-isolation infrared (MI-IR) spectroscopy is the isolation of single guest molecules in a host system at cryogenic conditions. The matrix mostly hinders rotation of the guest molecule, providing access to pure vibrational features. Vibrational self-consistent field (VSCF) and configuration interaction computations (VCI) on ab initio multimode potential energy surfaces (PES) give rise to anharmonic vibrational spectra. In a single-sourced combination of these experimental and computational approaches, we have established an iterative spectroscopic characterization procedure. The present article reviews the scope of this procedure by highlighting the strengths and limitations based on the examples of water, carbon dioxide, methane, methanol, and fluoroethane. An assessment of setups for the construction of the multimode PES on the example of methanol demonstrates that CCSD(T)-F12 level of theory is preferable to compute (a) accurate vibrational frequencies and (b) equilibrium or vibrationally averaged structural parameters. Our procedure has allowed us to uniquely assign unknown or disputed bands and enabled us to clarify problematic spectral regions that are crowded with combination bands and overtones. Besides spectroscopic assignment, the excellent agreement between theory and experiment paves the way to tackle questions of rather fundamental nature as to whether or not matrix effects are systematic, and it shows the limits of conventional notations used by spectroscopists.

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Infrared cryogenic studies

Cited by 12 publications

References 16 publications

Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C₃H₇X where X = F, Cl, and Br

On the synergy of matrix-isolation infrared spectroscopy and vibrational configuration interaction computations

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Infrared cryogenic studies

Cited by 12 publications

References 16 publications

Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

Generation and IR spectra of ionic and molecular complexes of aluminum chloride with tert- and sec-butyl chlorides

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C3H7X where X = F, Cl, and Br

On the synergy of matrix-isolation infrared spectroscopy and vibrational configuration interaction computations

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Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C₃H₇X where X = F, Cl, and Br