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  • 1
    Electronic Resource
    Electronic Resource
    Spectra and Structure of Silicon-Containing Compounds. XXV. Raman and Infrared Spectra, r 0 Structural Parameters, Vibrational Assignment, and Ab Initio Calculations of Ethyl Chlorosilane-Si-d2 (1999)
    Springer
    Structural chemistry 10 (1999), S. 333-348 
    Details
    ISSN: 1572-9001
    Keywords: Structural parameters ; internal rotational barriers ; ab initio calculations ; ethyl chlorosilane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The infrared (3200 to 400 cm−1) spectra of gaseous and solid and Raman (3200 to 20 cm−1) spectra of liquid and solid ethyl chlorosilane-Si-d2, CH3CH2SiD2Cl, have been recorded. Both the gauche and trans conformers have been identified in the fluid phases, but only the gauche conformer remains in the solid phase. Variable temperature (−105 to −150°C) studies of the infrared spectra of CH3CH2SiH2Cl dissolved in liquid krypton have been carried out. From these data, the enthalpy difference has been determined to be 78±11 cm−1 (0.93±0.13 kJ/mol), with the gauche conformer the more stable form. Utilizing the frequencies of the silicon-hydrogen stretches, from the chlorosilane-Si-d isotopomer, Si—H bond distances of 1.481 and 1.480 Å have been obtained for the gauche conformer and 1.481 Å for the trans conformer. Complete vibrational assignments are proposed for both isotopomers which are consistent with the predicted frequencies utilizing the force constants from ab initio MP2/6-31G(d) calculations. Both the infrared intensities and the Raman activities and depolarization values have been obtained from the ab initio calculations. Complete equilibrium geometries have been determined by ab initio calculations employing the 6-31(d), 6-311++G(d,p), and 6-311+G(2d,2p) basis sets with full electron correlation by the Moller–Plesset (MP) perturbation method to second order. Continuing the previously reported rotational constants from five different isotopomers and the ab initio predicted structural parameters, adjusted r 0 parameters have been calculated, which are compared to the corresponding r s parameters. The results are discussed and the theoretical values are compared to the experimental values when appropriate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022087310109
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational and Structural Studies of 1-Fluoropropane from Temperature Dependant FT-IR Spectra of Rare Gas Solutions and Ab Initio Calculations (1999)
    Springer
    Structural chemistry 10 (1999), S. 445-461 
    Details
    ISSN: 1572-9001
    Keywords: Conformational stabilities ; FT-IR spectra ; rare gas solutions ; 1-fluoropropane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Variable temperature (−55 to −150°C) studies of the infrared spectra (3500 to 400 cm−1) of 1-fluoropropane, CH3CH2CH2F, dissolved in liquid krypton and xenon have been recorded. Utilizing three conformer pairs in the krypton solution and four conformer pairs in the xenon solution, enthalpy differences of 104±6 cm−1 (1.24±0.07 kJ/mol) and 99±5 cm−1 (1.16±0.06 kJ/mol) were obtained from the krypton and xenon solutions, respectively, with the gauche form the more stable conformer. From these data it is estimated that 24% of the trans forms is present at ambient temperature. The conformational stabilities, harmonic force constants, fundamental frequencies, infrared intensities and Raman activities have been obtained from RHF/6-31G(d) and/or MP2/6-31G(d) ab initio calculations and these quantities have been compared to the experimental values when appropriate. The optimized geometries have also been obtained with several different ab initio basis sets up to MP2/6-311+G(2d,2p). The r0 structural parameters have been obtained by combining the ab initio data with the previously reported rotational constants for both conformers. The results are compared to the corresponding results for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022483207135
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational Studies of Methyl Vinyl Silane from Temperature-Dependent FT–IR Spectra of Xenon and Krypton Solutions (2000)
    Springer
    Structural chemistry 11 (2000), S. 229-240 
    Details
    ISSN: 1572-9001
    Keywords: Conformational stability ; variable-temperature FT–IR spectra ; krypton solutions ; methyl vinyl silane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Variable-temperature (−55 to −155°C) studies of the infrared spectra (3500–400 cm−1) of methyl vinyl silane, CH2CHSiH2CH3, dissolved in liquid xenon and krypton have been recorded. Utilizing three sets of conformer doublets due to the cis and gauche rotamers, the enthalpy difference has been determined to be 133 ± 11 cm−1 (1.59 ± 0.13 kJ/mol) with the gauche conformer the more stable form in the krypton solution. In the xenon solution, the enthalpy difference could not be determined because the infrared bands become so broad and the overlap was so extensive that meaningful areas could not be determined. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311+G(2d,2p) from which structural parameters and conformational stabilities have been determined. With the largest basis set, the cis conformer is predicted to be the more stable conformer, which is inconsistent with the experimental results. Utilizing previously reported microwave rotational constants for both conformers along with the ab initio predicted distances and angles, r 0 parameters have been obtained for both the cis and gauche conformers. The spectroscopic and theoretical results are compared to the corresponding quantities for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009258109080
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  • 4
    Electronic Resource
    Electronic Resource
    Spectra and Structures of Silicon-Containing Compounds. XXIV.* Raman and Infrared Spectra, r 0 Structural Parameters, Vibrational Assignment, Barriers to Internal Rotation, and Ab Initio Calculations of Ethylsilane (1998)
    Springer
    Structural chemistry 9 (1998), S. 255-264 
    Details
    ISSN: 1572-9001
    Keywords: Structural parameters ; internal rotational barriers ; ab initio calculations ; ethylsilane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The infrared (3200 to 400 cm−1) and Raman (3200 to 20 cm−1) spectra of gaseous and solid ethylsilane, CH3CH2SiH3, have been recorded. Additionally, the Raman spectrum of the liquid has been obtained with quantitative depolarization values. The SiH3 torsional mode has been observed as sum and difference bands with the silicon-hydrogen stretching vibration. Utilizing the torsional fundamental frequency of 132 cm−1 the threefold periodic barrier of 590 cm−1 (7.06 kJ/mol) has been obtained. Utilizing the frequencies of the silicon-hydrogen stretches, Si-H bond distances of 1.485 and 1.484 Å have been obtained for the bonds gauche and trans to the methyl group, respectively. Using previously reported rotational constants from seven different isotopomers, the r 0 parameters have been calculated and are compared to the corresponding r s parameters. A complete vibrational assignment is proposed that is consistent with the predicted frequencies utilizing the force constants from ab initio MP2/6-31G(d) calculations. Both the infrared intensities as well as the Raman activities and depolarization values have been obtained from the ab initio calculations. Complete equilibrium geometries have been determined by ab initio calculations employing the 6-31G(d), 6-311 + G(d,p), and 6-311+G(2d,2p) basis sets at levels of restricted Hartree–Fock (RHF) and/or Moller–Plesset (MP) to second order. The results are discussed and the theoretical values are compared to the experimental values when appropriate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022426829370
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  • 5
    Electronic Resource
    Electronic Resource
    Conformational Stability, Raman and Infrared Spectra, Vibrational Assignment, and Ab Initio Calculations of Allyltrifluorosilane (1999)
    Springer
    Structural chemistry 10 (1999), S. 1-15 
    Details
    ISSN: 1572-9001
    Keywords: Conformational stability ; structural parameters ; infrared and Raman intensities ; allyltrifluorosilane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Raman spectra (3500 to 30 cm−1) of allyltrifluorosilane, CH2CHCH2SiF3, in the liquid with quantitative depolarization ratios and solid states, and the infrared spectra (3500 to 30 cm−1) of the gas and solid have been recorded. Additionally, the mid-infrared spectra of the sample dissolved in liquified xenon as a function of temperature (−100° to −55°C) have been recorded. All of these data indicate there are two conformers, the more stable gauche rotamer and a very small amount of the cis conformer in the fluid states, but only the gauche form remains in the polycrystalline solid. The variable temperature studies of the infrared spectrum of the xenon solution indicate a relatively large enthalpy difference of 354±30 cm−1 (4.23±0.36 kJ/mol) between the conformers. The fundamental frequencies for the asymmetric (54 cm−1) and SiF3 (48 cm−1) torsions for the gauche conformer were observed in the far infrared spectrum, and from the SiF3 torsional frequency the barrier to internal rotation is calculated to have a value of 525 cm−1 (6.28 kJ/mol). A complete vibrational assignment is presented for the gauche conformer that is consistent with the predicted wavenumbers utilizing the force constants from ab initio MP2/6-31G* calculations. The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios, and vibrational wavenumbers have been obtained from RHF/6-31G* and/or MP2/6-31G* ab initio calculations. These quantities are compared to the corresponding experimental quantities when appropriate as well as with corresponding results for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022061710477
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  • 6
    Electronic Resource
    Electronic Resource
    Conformational Stability, Structural Parameters, Vibrational Frequencies, and Raman and Infrared Intensities of Allylsilane (1998)
    Springer
    Structural chemistry 9 (1998), S. 265-277 
    Details
    ISSN: 1572-9001
    Keywords: Conformational stability ; structural parameters ; infrared and Raman intensities ; allylsilane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Raman spectra (3500 to 30 cm−1) of allylsilane, CH2CHCH2SiH3, in the liquid with quantitative depolarization ratios and solid states and the infrared spectra (3500 to 30 cm−1) of the gas and solid have been recorded. Similar data have also been recorded for the Si-d3 isotopomer. Additionally, the mid-infrared spectra of the normal sample dissolved in liquified xenon as a function of temperature (−100 to −50°C) have been recorded. All these data indicate there is a single conformer, the gauche rotamer, in all three physical states. Utilizing the Si-H stretching frequencies from the infrared spectrum of the gaseous CH2CHCH2SiD2H isotopomer, the three Si-H bond distances (r 0) are calculated to be 1.484 Å for the gauche conformer. The other r 0 parameters are estimated from the previously reported rotational constants. The fundamental frequencies for the asymmetric (78 cm−1) and SiH3 (137 cm−1) torsions were obtained from sum and difference bands with the SiH3 stretches. From the SiH3 torsional frequency the barrier to internal rotation is calculated to have a value of 731 cm−1 (8.74 kJ/mol). The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios, and vibrational frequencies have been obtained from RHF/6-31G* and/or MP2/6-31G* ab initio calculations. These quantities are compared to the corresponding experimental quantities when appropriate as well as with some corresponding results for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022478913441
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  • 7
    Electronic Resource
    Electronic Resource
    Spectra and structure of silicon containing compounds (1995)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 352 (1995), S. 499-507 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Raman (50 to 3200 cm−1) and infrared (50 to 3500 cm−1) spectra of chlorodimethylmethoxysilane, Cl(CH3)2SiOCH3, in the vapor and solid phases have been recorded. Raman spectra of the liquid including depolarization ratios have also been recorded. Optimized geometries and conformational stabilities have been obtained from ab initio calculations utilizing the RHF/3–21G* and RHF/6–31G* basis sets. The calculations from both of these basis sets indicated the gauche conformer to be significantly more stable than the trans conformer. Since the gauche has twice the multiplicity of the trans form it is unlikely that the trans conformer will be detected in the fluid phases at room temperature. This is supported by the fact that no infrared or Raman bands were found to vanish in the spectra of the crystalline solid. The vibrational frequencies have been calculated using appropriate scaling factors, and the vibrational spectra are interpreted in detail. The results have been compared with those obtained for some related molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323375
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  • 8
    Electronic Resource
    Electronic Resource
    Raman and infrared spectra, conformational stability, barrier to internal rotation, and ab initio calculations for 1,1-dichloromethyl methyl ether (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 747-760 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman (3200-30 cm-1) and infrared (3200-50 cm-1) spectra of 1,1-dichloromethyl methyl ether are reported for the gas, liquid, amorphous solid and annealed polycrystalline solid. These spectral data were interpreted on the basis that in the fluid phases there is a mixture of trans and gauche conformers but only the trans conformer remains in the annealed solid. From the temperature-dependent relative intensity of Raman bands at 379 and 427 cm-1 in the liquid, an enthalpy difference of 656 ± 84 cm-1 (1.88 ± 0.24 kcal mol-1 or 7.85 ± 1.0 kJ mol-1) was obtained with the trans conformer the more stable form. Complete vibrational assignments are made for the much more abundant trans form, and a number of fundamentals are assigned for the gauche conformer with the aid of ab initio computations made with the 3-21G and 6-31G* basis sets. The harmonic force fields obtained using the 3-21G basis set are reported for both conformers together with scaled and unscaled wavenumbers and the accompanying potential energy distributions. The results are compared with the corresponding quantities obtained for some similar molecules.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250250903
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  • 9
    Electronic Resource
    Electronic Resource
    Raman and infrared spectra, conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of 3-bromo-2-methylpropene (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 767-780 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman (3200-20 cm-1) and infrared (3200-35 cm-1) spectra of 3-bromo-2-methylpropene, H2C=C(CH3)CH2Br were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The fundamental asymmetric torsional mode for the gauche conformer is observed at 81.5 cm-1 with one excited state falling at a lower wavenumber but the asymmetric torsion is not observed for the higher energy s-cis conformer. Utilizing the gauche observed torsional wave numbers, the gauche dihedral angle, the enthalpy difference between conformers and the calculated torsional fundamental wavenumber for the s-cis conformer, the potential function governing the interconversion of the rotamers was estimated. This potential function gives values of 170 cm-1 (486 cal mol-1) (1 cal = 4.184 J), 2659 cm-1 (7.60 kcal mol-1) and 725 cm-1 (2.07 kcal mol-1) for the s-cis to gauche, gauche to gauche and gauche to s-cis barriers, respectively, and it is compared with tht obtained with the RHF/STO-3G* basis set. From the methyl torsional wavenumber of 172 cm-1 for the gauche conformer, the threefold barrier of 695 cm-1 (1.99 kcal mol-1) was calculated for the methyl group. A complete vibrational assignment is proposed based on Raman : depolarization data, group wavenumbers and relative infrared and Raman intensities. The conformational energy difference and optimized geometries of both conformers were also obtained from ab initio calculations with the RHF/STO-3G*, RHF/LANL1DZ and MP2/LANL1DZ basis sets. Normal-coordinate analyses were also performed with force fields determined from both the RHF/STO-3G* and RHF/LANL1DZ basis sets. The calculated wavenumbers support the proposed vibrational assignment. These data are compared with the corresponding data for some similar molecules.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250250905
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  • 10
    Electronic Resource
    Electronic Resource
    Raman and infrared spectra, conformational stability, barriers to internal rotation and ab initio calculations of allyl cyanide (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 907-921 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman (3200-10 cm-1) and infrared (3150-50 cm-1) spectra of allyl cyanide, CH2=CHCH2CN, were recorded for the gas and solid phases. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. Both the cis and gauche conformers are present in the gas and liquid phases with the cis conformer being the more stable rotamer and the only conformer present in the annealed solid. The fundamental asymmetric torsion of the cis conformer has been observed in the far-infrared spectrum of the gas at 141.3 cm-1 with three excited states falling to lower wavenumbers. The corresponding fundamental for the gauche conformer has been observed in the Raman spectrum of the gas at ca. 102 cm-1. From temperature-dependent studies of the Raman spectrum of the liquid, three pairs of conformer peaks have been used to determine the ΔH value of 245 ± 6 cm-1 (707 ± 17 cal mol-1), with the cis conformer the most stable rotamer. Additionally, a variable-temperature study of the infrared spectrum of the sample dissolved in liquified xenon gives a ΔH of 336 ± 61 cm-1 (961 ± 175 cal mol-1), which should closely represent the ΔH value for the gas. Utilizing the torsional transitions, the enthalpy difference and the gauche dihedral angle, the potential function governing the conformational interchange was determined. A complete vibrational assignment is proposed for the cis conformer and several fundamentals are identified for the gauche rotamer based on infrared band contours, Raman depolarization data, group wavenumbers, relative intensities and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation, structural parameters and fundamental vibrational wavenumbers are compared with those obtained from ab initio gradient calculations employing the RHF/3-21G, RHF/6-31G* and/or MP2/6-31G* basis sets and to the corresponding quantities obtained for some similar molecules.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250251203
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