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Title
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Vibrational spectra, conformational stability, barriers to internal rotation, structural parameters and **ab initio** calculations of fluoromethyl methyl ether
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Author
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Abstract
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| The far-infrared spectrum of gaseous fluoromethyl methyl ether, FCH2OCH3, along with three of the deuterium isotopes, has been recorded at a resolution of 0. 10 cm-1 in the 350 to 50 cm-1 region. The fundamental asymmetric torsional and methyl torsional modes are extensively mixed and have been observed at 182 and 132 cm-1, respectively, for the stable gauche conformer with the lower frequency band having several excited states falling to lower frequency. An estimate is given for the potential function governing the asymmetric rotation. On the basis of a one-dimensional model the barrier to internal rotation of the methyl moiety is determined to be 527 +/- 9 cm-1 (1.51 +/- 0.03 kcal/mol). A complete assignment of the vibrational fundamentals for all four isotopic species observed from the infrared (3500 to 50 cm-1) spectra of the gas and solid and from the Raman (3200 to 10 cm- 1) spectra of the gas, liquid, and solid is proposed. No evidence could be found in any of the spectra for the high-energy trans conformer. All of these data are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing the 3-21G and 6-31G* basis sets along with the 6-31G* basis set with electron correlation at the MP2 level. Additionally, complete r0 geometries have been determined from the previously reported microwave data and carbon-hydrogen distances determined from infrared studies. The heavy-atom structural parameters (distances in angstrom, angles in degrees) are r(C1-F) = 1.395 +/- 0.005; r(C1-0) = 1.368 +/- 0.007; r(C2-O) = 1.426 +/- 0.003; less than with right parenthesis through FC1O = 11 1.33 = 0.25; less than with right parenthesis through C1OC2 = 113.50 +/- 0.18 and dih FC1OC2 = 69.12 +/- 0.26. All of these results are discussed and compared with the corresponding quantities obtained for some similar molecules. |
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Language
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English
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Source (journal)
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Structural chemistry. - Deerfield Beach, Fla
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Publication
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Deerfield Beach, Fla
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1993
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ISSN
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1040-0400
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DOI
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10.1007/BF00677371
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Volume/pages
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4
:2
(1993)
, p. 103-126
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ISI
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A1993LB12900004
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Full text (Publisher's DOI)
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