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Michael W P Petryk - One of the best experts on this subject based on the ideXlab platform.
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Site−Site Potentials in Neopentane and Tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
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site site potentials in Neopentane and tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
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through space coupling and fermi resonances in Neopentane d0 d6 d9 and tetramethylsilane
Journal of Physical Chemistry A, 2002Co-Authors: Michael W P Petryk, Bryan R HenryAbstract:A comparison of the CH vibrational overtone spectra of vapor phase Neopentane-d0 (C(CH3)4), -d6 (C(CH3)2(CD3)2), and -d9 (C(CH3)(CD3)3) and tetramethylsilane (TMS) in the frequency range ΔvCH = 4−8 (10 800−18 200 cm-1) has revealed pronounced differences between the spectra of TMS and the Neopentanes, and subtle differences among the spectra of the Neopentanes. These spectral differences are interpreted as a manifestation of geometry and vibrational frequency dependent differences in coupling efficiencies that facilitate the de-excitation of local modes of vibration via IVR. Fermi resonance plays a key role in this coupling. Some of the states are perturbed by through space coupling (a collision-like van der Waals interaction) that can facilitate IVR. The normal modes of vibration, which are implicated in Fermi resonance of the Neopentanes and TMS, have been calculated ab initio using density functional theory and are shown to be affected by through space interactions.
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Overtone intensities in Neopentane and tetramethylsilane
Canadian Journal of Chemistry, 2001Co-Authors: Michael W P Petryk, Bryan R HenryAbstract:The CH vibrational overtone transitions of vapour phase Neopentane-d0 ,- d6 ,- d9, and tetramethylsilane (TMS) are investigated via conventional absorbance spectroscopy and intracavity laser photoacoustic spectroscopy (ICL-PAS). The CH stretching overtones of Neopentane-d0 are observed in the energy range 1vCHD 3-9 (8 400 to 22 000 cm 1 ) and in the range 1vCHD 3-8 for the remaining Neopentanes and TMS. While we have extended the range of previous studies, our main focus in this work has been on overtone intensities. The oscillator strengths of the Neopentane- d0 overtone transitions are determined directly by conventional absorbance spectroscopy for 1vCHD 3-6 and via ICL-PAS with methane as an internal standard for 1vCHD 4-7. The correspondence of measured intensities for the two techniques demonstrates the usefulness of the latter for higher overtone ICL-PAS spectra. The experimentally determined Morse parameters e and e as well as the harmonically coupled anharmonic oscillator (HCAO) model are used in conjunction with dipole moment functions that are derived from ab initio computations to calculate overtone transition intensities for the Neopentanes and TMS.
Bryan R Henry - One of the best experts on this subject based on the ideXlab platform.
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Site−Site Potentials in Neopentane and Tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
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site site potentials in Neopentane and tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
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through space coupling and fermi resonances in Neopentane d0 d6 d9 and tetramethylsilane
Journal of Physical Chemistry A, 2002Co-Authors: Michael W P Petryk, Bryan R HenryAbstract:A comparison of the CH vibrational overtone spectra of vapor phase Neopentane-d0 (C(CH3)4), -d6 (C(CH3)2(CD3)2), and -d9 (C(CH3)(CD3)3) and tetramethylsilane (TMS) in the frequency range ΔvCH = 4−8 (10 800−18 200 cm-1) has revealed pronounced differences between the spectra of TMS and the Neopentanes, and subtle differences among the spectra of the Neopentanes. These spectral differences are interpreted as a manifestation of geometry and vibrational frequency dependent differences in coupling efficiencies that facilitate the de-excitation of local modes of vibration via IVR. Fermi resonance plays a key role in this coupling. Some of the states are perturbed by through space coupling (a collision-like van der Waals interaction) that can facilitate IVR. The normal modes of vibration, which are implicated in Fermi resonance of the Neopentanes and TMS, have been calculated ab initio using density functional theory and are shown to be affected by through space interactions.
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Overtone intensities in Neopentane and tetramethylsilane
Canadian Journal of Chemistry, 2001Co-Authors: Michael W P Petryk, Bryan R HenryAbstract:The CH vibrational overtone transitions of vapour phase Neopentane-d0 ,- d6 ,- d9, and tetramethylsilane (TMS) are investigated via conventional absorbance spectroscopy and intracavity laser photoacoustic spectroscopy (ICL-PAS). The CH stretching overtones of Neopentane-d0 are observed in the energy range 1vCHD 3-9 (8 400 to 22 000 cm 1 ) and in the range 1vCHD 3-8 for the remaining Neopentanes and TMS. While we have extended the range of previous studies, our main focus in this work has been on overtone intensities. The oscillator strengths of the Neopentane- d0 overtone transitions are determined directly by conventional absorbance spectroscopy for 1vCHD 3-6 and via ICL-PAS with methane as an internal standard for 1vCHD 4-7. The correspondence of measured intensities for the two techniques demonstrates the usefulness of the latter for higher overtone ICL-PAS spectra. The experimentally determined Morse parameters e and e as well as the harmonically coupled anharmonic oscillator (HCAO) model are used in conjunction with dipole moment functions that are derived from ab initio computations to calculate overtone transition intensities for the Neopentanes and TMS.
Martin L Sage - One of the best experts on this subject based on the ideXlab platform.
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Site−Site Potentials in Neopentane and Tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
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site site potentials in Neopentane and tetramethylsilane
Journal of Physical Chemistry A, 2005Co-Authors: Michael W P Petryk, Bryan R Henry, Martin L SageAbstract:Neopentane and TMS are used as model M(CH3)4 systems to investigate intramolecular interactions. The nonbonded site−site potential between two proximal hydrogen atoms on different methyl groups, Vnb(dHH), is not Lennard−Jones- or Morse-like but is found to be pseudolinear in hydrogen−hydrogen internuclear separation, dHH, for both Neopentane and TMS. The Morse potential is found to be a poor basis in which to expand Vnb(dHH). The nonbonded site−site potential is conformation-dependent and not transferable between molecules. The individual contributions to Vnb(dHH) are presented. The local mode parameters for Neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, dHH.
Bruce C. Gates - One of the best experts on this subject based on the ideXlab platform.
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Neopentane cracking catalyzed by iron- and manganese-promoted sulfated zirconia
Catalysis Letters, 1995Co-Authors: Tsz-keung Cheung, Julie L. D'itri, Friederike C. Lange, Bruce C. GatesAbstract:Cracking of Neopentane was catalyzed by a sulfated oxide of zirconium promoted with iron and manganese. Reaction at 300–450°C, atmospheric pressure, and Neopentane partial pressures of 0.00025–0.005 bar gave methane as the principal product, along with C_2 and C_3 hydrocarbons, butenes, and coke. The order of reaction in Neopentane was determined to be 1, consistent with a monomolecular reaction mechanism and with the formation of methane and t -butyl cations; the latter was presumably converted into several products, including only little isobutylene. At 450°C and a Neopentane partial pressure of 0.005 bar, the rate of cracking at 5 min onstream was 5×10^−8 mol/(g of catalyst s). Under the same conditions, the rates observed for unpromoted sulfated zirconia and USY zeolite were 3×10^−8 and 6×10^−9 mol/ (g of catalyst s), respectively. The observation that the promoted sulfated zirconia is not much more active than the other catalysts is contrasted to published results showing that the former catalyst is more than two orders of magnitude more active than the others for n -butane isomerization at temperatures
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Neopentane cracking catalyzed by iron and manganese promoted sulfated zirconia
Catalysis Letters, 1995Co-Authors: Tsz-keung Cheung, Friederike C. Lange, Julie L Ditri, Bruce C. GatesAbstract:Cracking of Neopentane was catalyzed by a sulfated oxide of zirconium promoted with iron and manganese. Reaction at 300–450°C, atmospheric pressure, and Neopentane partial pressures of 0.00025–0.005 bar gave methane as the principal product, along with C2 and C3 hydrocarbons, butenes, and coke. The order of reaction in Neopentane was determined to be 1, consistent with a monomolecular reaction mechanism and with the formation of methane andt-butyl cations; the latter was presumably converted into several products, including only little isobutylene. At 450°C and a Neopentane partial pressure of 0.005 bar, the rate of cracking at 5 min onstream was 5×10−8 mol/(g of catalyst s). Under the same conditions, the rates observed for unpromoted sulfated zirconia and USY zeolite were 3×10−8 and 6×10−9 mol/ (g of catalyst s), respectively. The observation that the promoted sulfated zirconia is not much more active than the other catalysts is contrasted to published results showing that the former catalyst is more than two orders of magnitude more active than the others forn-butane isomerization at temperatures <100°C. The results raise a question about whether the superacidity attributed to sulfated zirconia as a low-temperature butane isomerization catalyst pertains at the high temperatures of cracking.
Tsz-keung Cheung - One of the best experts on this subject based on the ideXlab platform.
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Neopentane cracking catalyzed by iron- and manganese-promoted sulfated zirconia
Catalysis Letters, 1995Co-Authors: Tsz-keung Cheung, Julie L. D'itri, Friederike C. Lange, Bruce C. GatesAbstract:Cracking of Neopentane was catalyzed by a sulfated oxide of zirconium promoted with iron and manganese. Reaction at 300–450°C, atmospheric pressure, and Neopentane partial pressures of 0.00025–0.005 bar gave methane as the principal product, along with C_2 and C_3 hydrocarbons, butenes, and coke. The order of reaction in Neopentane was determined to be 1, consistent with a monomolecular reaction mechanism and with the formation of methane and t -butyl cations; the latter was presumably converted into several products, including only little isobutylene. At 450°C and a Neopentane partial pressure of 0.005 bar, the rate of cracking at 5 min onstream was 5×10^−8 mol/(g of catalyst s). Under the same conditions, the rates observed for unpromoted sulfated zirconia and USY zeolite were 3×10^−8 and 6×10^−9 mol/ (g of catalyst s), respectively. The observation that the promoted sulfated zirconia is not much more active than the other catalysts is contrasted to published results showing that the former catalyst is more than two orders of magnitude more active than the others for n -butane isomerization at temperatures
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Neopentane cracking catalyzed by iron and manganese promoted sulfated zirconia
Catalysis Letters, 1995Co-Authors: Tsz-keung Cheung, Friederike C. Lange, Julie L Ditri, Bruce C. GatesAbstract:Cracking of Neopentane was catalyzed by a sulfated oxide of zirconium promoted with iron and manganese. Reaction at 300–450°C, atmospheric pressure, and Neopentane partial pressures of 0.00025–0.005 bar gave methane as the principal product, along with C2 and C3 hydrocarbons, butenes, and coke. The order of reaction in Neopentane was determined to be 1, consistent with a monomolecular reaction mechanism and with the formation of methane andt-butyl cations; the latter was presumably converted into several products, including only little isobutylene. At 450°C and a Neopentane partial pressure of 0.005 bar, the rate of cracking at 5 min onstream was 5×10−8 mol/(g of catalyst s). Under the same conditions, the rates observed for unpromoted sulfated zirconia and USY zeolite were 3×10−8 and 6×10−9 mol/ (g of catalyst s), respectively. The observation that the promoted sulfated zirconia is not much more active than the other catalysts is contrasted to published results showing that the former catalyst is more than two orders of magnitude more active than the others forn-butane isomerization at temperatures <100°C. The results raise a question about whether the superacidity attributed to sulfated zirconia as a low-temperature butane isomerization catalyst pertains at the high temperatures of cracking.