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@PHDTHESIS{Andresen:812167,
      author       = {Andresen, Maike},
      othercontributors = {Lüchow, Arne and Cuisset, Arnaud and Schmitt, Michael},
      title        = {{S}tructures and internal dynamics of ketones studied by
                      microwave spectroscopy and quantum chemistry},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2021-01709},
      pages        = {1 Online-Ressource (XVI, 291 Seiten)},
      year         = {2021},
      note         = {Cotutelle-Dissertation. - Veröffentlicht auf dem
                      Publikationsserver der RWTH Aachen University; Dissertation,
                      RWTH Aachen University, 2021. - Dissertation, Université
                      Paris-Est, 2021},
      abstract     = {In this dissertation, diverse ketones containing an acetyl
                      methyl group were studied by microwave spectroscopy with the
                      main focus on the effects of internal rotations. As a result
                      a “barrier class system” was introduced, which firmly
                      links the barrier to internal rotation of the acetyl methyl
                      group to the characteristic structure of the molecule. The
                      acetyl methyl barrier thus functions as a “structural
                      detector”. The analysis was supplemented by quantum
                      chemical calculations of molecular parameters. For a series
                      of methyl n-alkyl ketones, including pentan-2-one,
                      hexan-2-one, heptan-2-one and octan-2-one, at least two
                      conformers could be identified in the spectrum of each of
                      these aliphatic ketones: one with C1 and one with Cs
                      symmetry. The barriers to internal rotation of the acetyl
                      methyl group of the C1 conformers were determined to always
                      be about 240 cm−1. In case of the Cs conformers, the
                      barrier heights are found to be approximately 180 cm−1.
                      These conformers are hence members of the “C1” and “Cs
                      class”, respectively. Only for hexan-2-one, a third
                      conformer showing another specific C1 structure and a
                      barrier height of 182 cm−1 was assigned. Furthermore,
                      spectral splittings caused by the internal rotation of the
                      methyl group at the end of the respective alkyl chain were
                      observed. Here, the barriers are about 1000 cm−1 for each
                      conformer. E-3-Penten-2-one and 3-methyl-3-buten-2-one are
                      α,β-unsaturated ketones and members of the “mesomeric
                      class”. They exhibit complicated splitting patterns in the
                      spectrum arising due to the internal rotation of the acetyl
                      methyl group, as well as of the methyl group attached to the
                      propenyl or isopropenyl group, respectively. For
                      E-3-penten-2-one, two conformers were assigned, one with
                      antiperiplanar (ap) and one with synperiplanar (sp)
                      structure. In case of 3-methyl-3-buten-2-one, only the ap
                      conformer could be identified. The acetyl methyl torsional
                      barriers range from 350 cm−1 to 520 cm−1, while they are
                      about 600 cm−1 for the propenyl and isopropenyl methyl
                      groups. In the microwave spectrum of 3-methylbutan-2-one, a
                      branched ketone, additional splittings beside those due to
                      internal rotation were observed. They are probably caused by
                      a tunnelling motion between two enantiomeric versions of the
                      molecule. Therefore, 3-methylbutan-2-one is a member of the
                      “tunnelling class”.},
      cin          = {153420 / 150000},
      ddc          = {540},
      cid          = {$I:(DE-82)153420_20140620$ / $I:(DE-82)150000_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2021-01709},
      url          = {https://publications.rwth-aachen.de/record/812167},
}