Bracketing subtle conformational energy differences between self-solvated and stretched trifluoropropanol†
Matthias Heger,Katharina E. Otto,Ricardo A. Mata,Martin A. Suhm
Physical Chemistry Chemical Physics Pub Date : 03/17/2015 00:00:00 , DOI:10.1039/C4CP05868B
Abstract

The intramolecular OH⋯F hydrogen bond in 3,3,3-trifluoropropanol (TFP) exerts a subtle stabilizing effect that, when compared to the non-fluorinated analog, reorders the five distinguishable conformers and widens the gap between the two most stable structures. Here, we combine findings from Raman spectroscopy in supersonic expansions and high-level quantum-chemical calculations to bracket the energy difference between the two most stable TFP structures at 1.7(5) kJ mol−1. The torsional potential energy surface suggests consecutive backbone and OH torsional motions for the conformer interconversion, which are discussed in the framework of supersonic jet cooling as a function of nozzle temperature. The picture of a bistable cold molecule with trans or gauche backbone emerges, in which the OH group controls the energy difference and modulates the high barrier separating the heavy atom frames.

Graphical abstract: Bracketing subtle conformational energy differences between self-solvated and stretched trifluoropropanol