Perfluoro-1,2-dioxolane. A new synthesis and its gas-phase structure

Abstract

Highly pure perfluoro-1,2-dioxolane was prepared in good yields by fluorination of 2,2-difluoropropanedioyl difluoride with elemental fluorine in the presence of CsF. A gas-phase electron diffraction study results for the five-membered ring in a half-chair conformation possessing C 2 symmetry and the following geometric parameters ( r a distances and ∠ α angles, error limits are 3σ values and refer to the last digit): OO = 144.3(11) pm, OC = 137.7(15) pm, CC = 153.1(5) pm, (CF) mean = 131.8(4) pm, CCC = 98.1(13)°, CCO = 107.3(12)°, COO = 102.9(9)°, FCF = 109.8(9)° and the torsional angle around the OO bond τ(COOC) = 48(2)°. Ab initio calculations (HF/4-21G and HF/4-21G*) confirm that this half-chair conformation is the only stable structure along the pseudorotational path and they reproduce the geometric parameters reasonably well.