High-Resolution Infrared Spectroscopy in the 1200−1300 cm-1 Region and Accurate Theoretical Estimates for the Structure and Ring-Puckering Barrier of Perfluorocyclobutane

Mechanism of Reductive Fluorination by PTFE-Decomposition Fluorocarbon Gases for WO3

Reductive fluorination, which entails the substitution of O^2- from oxide compounds with F^- from fluoropolymers, is considered a practical approach for preparing transition-metal oxyfluorides. However, the current understanding of the fundamental reaction paths remains limited due to the analytical complexities posed by high-temperature reactions in glassware. Therefore, to expand this knowledgebase, this study investigates the reaction mechanisms behind the reductive fluorination of WO₃ using polytetrafluoroethylene (PTFE) in an Ni reactor. Here, we explore varied reaction conditions (temperature, duration, and F/W ratio) to suppress the formation of carbon byproducts, minimize the dissipation of fluorine-containing tungsten (VI) compounds, and achieve a high fluorine content. The gas-solid reaction paths are analyzed using infrared spectroscopy, which revealed tetrafluoroethylene (C₂F₄), hexafluoropropene (C₃F₆), and iso-octafluoroisobutene (i-C₄F₈) to be the reactive components in the PTFE-decomposition gas during the reactions with WO₃ at 500 °C. CO₂ and CO are further identified as gaseous byproducts of the reaction evincing that the reaction is prompted by difluorocarbene (:CF₂) formed after the cleavage of C═C bonds in i-C₄F₈, C₃F₆, and C₂F₄ upon contact with the WO₃ surface. The solid-solid reaction path is established through a reaction between WO₃ and WO_3-xF_x where solid-state diffusion of O^2- and F^- is discerned at 500 °C.

Pseudorotation in pyrrolidine: rotational coherence spectroscopy and ab initio calculations of a large amplitude intramolecular motion

Pseudorotation in the pyrrolidine molecule was studied by means of femtosecond degenerate four-wave mixing spectroscopy both in the gas cell at room temperature and under supersonic expansion. The experimental observations were reproduced by a fitted simulation based on a one-dimensional model for pseudorotation. Of the two conformers, axial and equatorial, the latter was found to be stabilized by about 29 +/- 10 cm(-1) relative to the former one. The barrier for pseudorotation was determined to be 220 +/- 20 cm(-1). In addition, quantum chemical calculations of the pseudorotational path of pyrrolidine were performed using the synchronous transit-guided quasi-Newton method at the MP2 and B3LYP levels of theory. Subsequent CCSD(T) calculations yield the energy preference of the equatorial conformer and the barrier for pseudorotation to be 17 and 284 cm(-1), respectively.