Rotational spectra of singly substituted rare isotopologues of two conformers of 3,3,3-trifluoropropanol

Rotational spectroscopy of hydrogen-bonded binary trifluoro-propanol conformers: conformational diversity, preference and abundances in a jet expansion

“…On the other hand, the abundance of a species may not be correctly predicted based on a simple thermodynamic model. For example, using the reported TFP conformational temperature (135 K), 24 the abundance of dimer 1 to dimer 14 was predicted to be 0.03 based on their relative ZPE corrected energies, in clear disagreement with the observed relative abundance of 0.2. Furthermore, the conformational temperature of a H-bonded dimer was reported to be as low as 45 K using a jet expansion, 59 which would lead to an even lower predicted abundance for dimer 14 versus 1 .…”

“…The conformation conversion between members of different binary families is highly unlikely in a jet expansion and each binary family is metastable, based on the reports that the conversions between different backbone family members have high barriers for the TFP monomer. 24,25 While the conformational conversion or cooling within a dimer family is generally possible, as elaborated below with theoretical supports.…”

“…This leads to nine conformations including four pairs of enantiomers which are transiently chiral, G− g +/G+ g −, T g −/T g +, G− t /G+ t , G− g −/G+ g +, and one achiral monomer, T t , whose zero-point-energy (ZPE) corrected relative energies are 0.0, 4.3, 6.4, 7.5, and 2.6 kJ mol −1 , respectively at the B3LYP-D3BJ/def2-TZVP level. 24 The geometries of these nine TFP conformations are shown in Fig. S1, (ESI†).…”

“…With this kinetic model the abundances of each binary family were predicted to be G−G− (34%), G−G+ (34%), GT (14%), TG (14%), and TT (3%), based on the experimental abundance of the monomer subunits: G (83%) and T (17%) and the statistical probabilities of the binary products. 24…”

“…19,20 In the current study, we applied jet-cooled CP-FTMW spectroscopy and a recently developed conformational searching tool, CREST, 21,22 to explore the rich conformational landscape of the 3,3,3-trifluoropropanol (TFP) dimer. The monomeric TFP conformers have been investigated with a static gas sample using microwave spectroscopy 23 and with a jet expansion using CP-FTMW 24 and Raman spectroscopy 25 where two TFP conformers were observed. So far, no spectroscopic investigations have been reported for the hydrogen (H)-bonded dimer.…”