Structural Analysis of Perfluoropropanoyl Fluoride in the Gas, Liquid, and Solid Phases

Abstract

The coexistence of two conformers in perfluoropropanoyl fluoride, CF3CF2C(O)F, differing in the CC-CF dihedral angle (gauche 85(10)% and anti 15(10)%), has been determined by means of gas-phase electron diffraction (GED). Quantum-chemical calculations performed at the MP2 and B3LYP approximations and cc-pVTZ basis sets reproduce the experimental values with confidence. By contrast, FTIR spectra give no clear evidence for the anti-conformer in the gas phase. Information on this less abundant but stable rotamer is obtained from matrix-isolation/FTIR spectroscopy and liquid Raman spectroscopy. In situ crystallization and single-crystal X-ray diffraction (XRD) data reveal the presence of solely the gauche-conformation in the solid state. A set of intermolecular interactions including C═O···C═O, C-F···F-C, and F···C═O is detected. The nature of bonding and the relative stabilities of gauche- and anti-conformers are explored using natural bond orbitals.

Effect of the Substituents on the Nature and Strength of Lone-Pair–Carbonyl Interactions in Acyl Halides

“…0.4 Å shorter than the sum of the van der Waals radii. However, the shortest C=O•••C=O contact is found at 2.803 Å (α = 96.5°) in the crystal structure of pentafluoropropanoyl fluoride (HALWUP), 24 in which there is also a F•••C=O contact at 3.129 Å, i.e. 0.1 Å…”

“…0.4 Å shorter than the sum of the van der Waals radii. However, the shortest CO••• CO contact is found at 2.803 Å (α = 96.5°) in the crystal structure of pentafluoropropanoyl fluoride (HALWUP), 24 in which there is also a F•••CO contact at 3.129 Å: i.e., 0.1 Å shorter than the sum of the corresponding van der Waals radii. In the crystal structure of FAYNOI, 25 in which the donor oxygen is an ether, the O•••C contact is found at a very short distance of 2.590 Å (Figure 2).…”

Organoelement Compounds Crystallized In Situ: Weak Intermolecular Interactions and Lattice Energies

“…In 2016, Norbert W. Mitzel and Carlos O. Della Védova's teams published a joint work in which perfluoropropanoic acid fluoride 56 (CF 3 CF 2 C(O)F) was described [67]. The structure of this compound was studied by gas electron diffraction, IR, Raman, and ultraviolet spectroscopy, and by quantum chemical calculations (MP2/cc-pVTZ and B3LYP/cc-pVTZ).…”