Intramolecular hydrogen bonding in (1-fluorocyclopropyl)methanol as studied by microwave spectroscopy and quantum chemical calculations

Abstract

(1-Fluorocyclopropyl)methanol has been studied by microwave spectroscopy in the 12–61 GHz spectral region. The rotational spectra of the ground and of four vibrationally excited states belonging to three different normal modes of one rotamer have been assigned. Most other cyclopropylmethanol derivatives prefer conformations stabilized by an internal hydrogen bond with the pseudo-π electrons along the edges of the ring. This is not the case for the title compound. The conformer assigned in this work has an internal hydrogen bond formed between the fluorine atom and the hydrogen atom of the hydroxyl group. This rotamer is at least 4 kJ/mol more stable than any other form of the molecule. It is pointed out that electrostatic interaction between the O–H and C–F bond dipoles can largely explain the conformational preference of this compound. The microwave work has been assisted by gas-phase infrared spectroscopy and quantum chemical calculations made at the MP2/6-311++G** and B3LYP/6-311++G** levels of theory.