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  • 1
    Electronic Resource
    Electronic Resource
    Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of 2-chloropropenoyl fluoride (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 905-917 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The far-infrared spectrum of gaseous 2-chloropropenoyl fluoride, CH2 CClCFO, has been recorded at a resolution of 0.10 cm−1 in the region of 350–35 cm−1. The fundamental asymmetric torsional frequencies of the more stable s-trans (two double bonds oriented trans to one another) and the high energy s-cis conformations have been observed at 67.80 and 49.96 cm−1, respectively, each with several excited states falling to lower frequencies. From these data the asymmetric torsional potential function governing the internal rotation about the C–C bond has been determined. The potential coefficients are V1 =−125±1, V2 =1586±6, V3 =375±2, V4 =−36±2, and V5 =−65±1 cm−1. The s-trans to s-cis and s-cis to s-trans barriers have been determined to be 1755 and 1570 cm−1, respectively, with an energy difference between the conformations of 185±9 cm−1 (529±26 cal/mol). From studies of the Raman spectrum at variable temperatures, the conformational enthalpy difference has been determined to be 176±40 cm−1 (503±114 cal/mol) and 625±51 cm−1 (1787±146 cal/mol) for the gas and liquid, respectively. A complete assignment of the vibrational fundamentals observed from the infrared spectra (3500–50 cm−1) of the gas and solid and the Raman spectra (3200–10 cm−1) of all three physical states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree–Fock gradient calculations employing both the 3-21G* and 6-31G* basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459117
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of 2-fluoropropenoyl fluoride (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7361-7373 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The far infrared spectrum of gaseous 2-fluoropropenoyl fluoride CH2CFCFO, has been recorded at a resolution of 0.10 cm−1 in the 350–35 cm−1 region. The asymmetric torsional fundamental of the more stable s-trans (two double bonds oriented trans to one another) and the high energy s-cis conformations have been observed at 84.1 and 68.5 cm−1, respectively, each with excited states falling to lower frequencies. From these data, the asymmetric torsional potential function governing internal rotation about the C–C bond has been determined. The potential coefficients are V1=−201±4, V2=2106±16, V3=382±6, V4=−41±5, and V5=−74±3 cm−1. The s-trans to s-cis and s-cis to s-trans barriers have been determined to be 2232 and 2124 cm−1, respectively, with an enthalpy difference between the conformations of 108±26 cm−1 (309±74 cal/mol). From variable temperature studies of the Raman spectrum, the conformational enthalpy difference has been determined to be 187±39 cm−1 (535±112 cal/mol) and 370±82 cm−1 (1058±234 cal/mol) for the gas and liquid, respectively. A complete assignment of the vibrational fundamentals observed from the infrared (3500–50 cm−1) spectra of the gas and solid and the Raman (3200–10 cm−1) spectra of all three physical states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree–Fock gradient calculations employing both the 3-21G and 6-31G* basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457259
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of fluoroacetyl chloride (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6840-6851 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The far infrared spectrum (375 to 35 cm−1) of gaseous fluoroacetyl chloride, CH2FC(O)C1, has been recorded at a resolution of 0.10 cm−1. The fundamental asymmetric torsions of the more stable trans (halogen atoms are trans) and the high energy cis conformations have been observed at 116.18 and 49.42 cm−1, respectively, each with several upper state transitions falling to lower frequency. From these spectral data, an asymmetric potential function has been calculated and the potential coefficients are: V1=43±6, V2=1039±36, V3=498±3, V4=149±21, and V6=−10±7 cm−1. The trans to cis and cis to trans barriers are 1455±25 cm−1 (4.16±0.07 kcal/mol) and 914±24 cm−1 (2.61±0.07 kcal/mol), respectively, with an enthalpy difference of 541±45 cm−1 (1.55±0.13 kcal/mol). From studies of the Raman spectra at variable temperatures, values of 509±37 cm−1 (1.46±0.10 kcal/mol) and 310±8 cm−1 (0.89±0.02 kcal/mol) have been determined for the enthalpy difference for the gas and liquid, respectively. The conformational stability, barriers to internal rotation, and fundamental vibrational frequencies which have been determined experimentally, are compared to those obtained from ab initio Hartree–Fock calculations employing both the 3-21G* and 6-31G* basis sets, and to the corresponding quantities obtained for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456257
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational stability and barriers to internal rotation of 2-methylpropanal by far infrared and microwave spectroscopy (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 738-751 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From the far infrared spectrum of 2-methylpropanal (isobutyraldehyde), (CH3)2CHCHO, in the gaseous state, the asymmetric torsion for the gauche conformer was observed as a series of Q branches at 75.0, 80.9, 85.8, and 90.3 cm−1 with similar transitions observed for (CD3)2CDCHO. Also from an investigation of the Raman spectrum of the gas a transition at ∼110 cm−1 has been tentatively assigned as the "double jump'' of the asymmetric torsion for the trans conformer. The microwave spectrum of the excited vibrational states for the light molecule has been investigated in the region from 12.5 to 40 GHz and, from relative intensity measurements, the frequencies of the asymmetric torsions were determined to be 72±7 and 50±20 cm−1 for the gauche and trans rotamers, respectively. Additionally, "tunneling'' splitting of 2.0±0.4 and 60.0±0.3 MHz has been observed for the second and third excited states, respectively, of the asymmetric torsion of the gauche conformer. From these data the asymmetric potential function has been calculated and the following potential constants have been evaluated: V1=−131±35, V2=−225±21, V3=555±10, V4=−70±5, V5=95±5, and V6=−140±10 cm−1 where the 1←0 transition of the gauche has been assigned at 75.0 cm−1. This potential function leads to an enthalpy difference of 250±66 cm−1 (715±189 cal/mol) which is in good agreement with the value of 248±35 cm−1 determined from variable temperature studies of the Raman spectrum of the gas. Analysis of the transitions observed between 250 and 150 cm−1 in the far infrared spectrum of the gas indicated that the two methyl rotors are coupled for the gauche conformer and the barriers to internal rotation of the methyl tops have been calculated to be 987 cm−1 (2.82 kcal/mol) and 1132 cm−1 (3.24 kcal/mol).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457126
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  • 5
    Electronic Resource
    Electronic Resource
    Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of chloroacetyl fluoride (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1285-1296 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The far infrared spectrum of gaseous chloroacetyl fluoride, CH2ClC(O)F, has been recorded at a resolution of 0.10 cm−1 in the 350 to 35 cm−1 region. The fundamental asymmetric torsional frequencies of the more stable trans (two halogen atoms oriented trans to one another) and high energy gauche (Cl–C–C=O torsional dihedral angle of 122°) have been observed at 86.5 and 48.8 cm−1, respectively, each with excited states falling to lower frequency. From these data the asymmetric torsional potential function governing internal rotation about the C–C bond has been determined. This potential function is consistent with torsional potential coefficients of: V1=350±12, V2=306±6, V3=420±1, V4=44±1, and V6=2±1 cm−1. The trans to gauche, gauche to gauche, and gauche to trans barriers have been determined to be 796, 245, and 271 cm−1, respectively, with an energy difference between the conformations of 525±24 cm−1 (1.50±0.07 kcal/mol). From studies of the Raman spectrum at variable temperatures the conformational energy difference has been determined to be 445±80 (1.27±0.2 kcal/mol) and 534±68 cm−1 (1.53±0.2 kcal/mol) for the gaseous and liquid phases, respectively. A complete assignment of the vibrational fundamentals observed from the infrared (3500 to 50 cm−1) spectra of the gaseous and solid states and Raman (3200 to 10 cm−1) spectra of the gaseous, liquid, and solid states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree–Fock gradient calculations employing both the 3-21G* and 6-31G* basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455718
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  • 6
    Electronic Resource
    Electronic Resource
    Spectra and structure of small ring compounds. XLVIII. Conformational stability of methylcyclobutane from low frequency Raman data of the gas (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 545-551 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The low frequency (500–80 cm−1) Raman spectra of gaseous methylcyclobutane, c-C4H7CH3, and methyl-d3-cyclobutane have been recorded. A series of Q branches beginning at 161 cm−1 for the light molecule and 154 cm−1 for the d3 compound with successive transitions falling to lower frequencies have been assigned to the ring puckering vibrations of both the low energy equatorial and high energy axial conformers. These data have been fitted to an asymmetric potential function of the form: V(cm−1)=(4.78±0.10)×105X4−(3.08±0.04)×104X2 +(2.18±0.1)×104X3 with an assumed reduced mass of 160 amu for the light compound. Utilizing this potential the difference between the puckering angles for the two conformers was calculated to be 4.3° with the equatorial conformer having the larger value of 20.7°. A similar potential was obtained for the d3 molecule. The energy difference between the equatorial and axial forms was found to be 247±20 cm−1 (706 cal/mol) and a barrier of 641±20 cm−1 (1.83 kcal/mol) was found for the interconversion. Experimental values for the ΔH of both the liquid (354±179 cm−1) and gas (295±75 cm−1) from relative intensities of different Raman band pairs over 85 and 37 °C temperature ranges, respectively, were found to be consistent with the value obtained from the potential function. These results are compared to the corresponding quantities for similar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452305
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  • 7
    Electronic Resource
    Electronic Resource
    Spectra and structure of small ring molecules. XLVII. Rotational and vibrational spectra and conformational stability of cyclobutylcarboxylic acid fluoride (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5446-5456 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of cyclobutylcarboxylic acid fluoride, c-C4H7CFO, has been recorded from 18.0 to 40.0 GHz. The a-type R-branch transitions have been observed and assigned for the ground and two vibrationally excited states of the asymmetric torsional mode as well as for the first vibrationally excited state of the ring puckering fundamental. The rotational constants were determined from the frequency fit to a rigid rotor model for the ground vibrational state to be: A=5467.35±0.03, B=1884.76±0.01, and C=1558.64±0.01 MHz. These constants are shown to be consistent with an equatorial-gauche conformation (i.e., the CFO group is in the equatorial position relative to the ring and the C=O bond is eclipsing, or nearly so, one of the C–C bonds of the ring). From relative intensity measurements the frequency for the asymmetric torsion for this conformer is estimated to be 72±10 cm−1. From the Stark effect the dipole moment components were determined to be: ||μa|| =2.97±0.02, ||μb|| =0.84±0.01, ||μc|| =0.35±0.01, and ||μt|| =3.11±0.01 D. The central line of an additional conformer has been identified with a B+C value of 3482 MHz which is consistent with the expected value for the equatorial-trans conformer. The infrared (3500 to 30 cm−1) and Raman spectra (3200 to 30 cm−1) have also been recorded for the gaseous and solid states of cyclobutylcarboxylic acid fluoride.Additionally, the Raman spectrum of the liquid phase has been recorded and qualitative depolarization values have been obtained. From the relative intensities of the Raman lines of the gas at 918 cm−1 (equatorial-trans) and 926 cm−1 (equatorial-gauche) as a function of temperature, the enthalpy difference was found to be 352±100 cm−1 (1.01 kcal/mol) with the equatorial-gauche being more stable. A complete vibrational assignment is proposed based on infrared band contours, depolarization values, and group frequencies. These results are compared to similar quantities for some related molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451555
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  • 8
    Electronic Resource
    Electronic Resource
    Vibrational spectra, normal-coordinate analysis, r0 structure, ab initio calculations, and conformational equilibrium of 3-fluoropropene (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 2877-2886 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100259a034
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational analysis, barriers to internal rotation, vibrational assignment, and ab initio calculations of 1,2-difluoroethane (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 8224-8233 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100200a006
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  • 10
    Electronic Resource
    Electronic Resource
    Spectra and structure of small ring compounds. 46. Infrared and Raman spectra, conformational stability, and vibrational assignment of cyclobutylsilane (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 4307-4317 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100266a032
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