A Direct Link from the Gas to the Condensed Phase: A Rotational Spectroscopic Study of 2,2,2‐Trifluoroethanol Trimers

Abstract

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The Chiral Trimer and a Metastable Chiral Dimer of Achiral Hexafluoroisopropanol: A Multi‐Messenger Study

“…Microwave spectra were recorded with a2 .0-6.0 GHz chirped pulse FTMW spectrometer [11,26,35] and ac avity-based FTMW spectrometer [36] with frequency uncertainties of about 12 kHz and about 2kHz, respectively.H FIP (Sigma Aldrich, 99.9 %) was used without further purification. Mixtures of 0.1 %H FIP in Ne (Praxair, 99.999 %) were preparedf or the measurements.T he nozzle stagnation pressure was kept at subambient pressures (ca.…”

“…However,t he Boltzmann-weighted relative intensity distributions for m b -a nd m c -type transitions track very differently at the experimental rotational temperature of about 0.5 Kinthis frequency region. [28] In the related 3,3,3trifluoroethanol trimer, [11] these effects provide at hermodynamic drive to stabilize a t-subunit, which is not stable in its monomeric form. While we observed the strongest m c transitions at about 3500-4000 MHz, the m b -type transitions in this region are expected to be approximately 5-10 times weaker than the m c -type transitions and below the detection limit of the experiment.…”

“…Therefore,whether the (ggg')trimer is considered as acombination of g + g + g' or g + gg', all subunits are in astate of high energy.These subunit disadvantages are compensated by amaximization of fluorous and other secondary contacts as well as the larger monomer dipole. [28] In the related 3,3,3trifluoroethanol trimer, [11] these effects provide at hermodynamic drive to stabilize a t-subunit, which is not stable in its monomeric form. [28] For2 -fluoroethanol (FE) tetramers, [29] one tetramer containing exclusively the least stable monomer subunits with an energy penalty of % 40 kJ mol À1 was predicted to be only 2kJmol À1 less stable than the global minimum although it was not observed experimentally.…”

“…[8] Theh omochiral dimer of trifluoroethanol has been particularly enigmatic,due to aheterochiral competitor very close in energy which was initially not observed at all [9] and later quantified at about 10 %i najet expansion experiment. [11] Since monomeric trifluoroethanol exists in at ransiently chiral ground-state conformation that can be rapidly interconverted via internal rotation of the hydroxyl group,i tm ay be less surprising that it forms chirality-synchronized oligomers. [11] Since monomeric trifluoroethanol exists in at ransiently chiral ground-state conformation that can be rapidly interconverted via internal rotation of the hydroxyl group,i tm ay be less surprising that it forms chirality-synchronized oligomers.…”

“…[10] Thet rimer of trifluoroethanol was recently shown to exhibit low-energy ring and chain conformations with different degrees of chirality synchronization. [11] Since monomeric trifluoroethanol exists in at ransiently chiral ground-state conformation that can be rapidly interconverted via internal rotation of the hydroxyl group,i tm ay be less surprising that it forms chirality-synchronized oligomers. Here,w es tudy the more intriguing and computationally more challenging case of 1,1,1,3,3,3-hexafluoro-propan-2-ol (HFIP).…”