Fluorine compounds

PTFE (Teflon) tape has been reported as an alternative to liquid perfluoroalkanes in fluorous phase-vanishing (PV) reactions. Previous research on PV-PTFE reactions found that PTFE tape has unique characteristics compared to liquid flourous phase screens, including reagent permeabilities that are altered by exposure to certain organic solvents. This study investigates these characteristics by observing the effects of solvent adsorption on the diffusion of bromine and dimethyl phthalate. The directionality of solute diffusion in PV-PTFE chemiluminescence was also studied. Literature on Teflon films and on PV reactions is utilized to explain how the structural and chemical features of PTFE tape influence its permeability, and how solvents alter this permeability. We use structural arguments to explain why chemically-identical bulk PTFE behaves differently from PTFE tape. By better understanding how PTFE tape functions in PV reactions, the method may be improved and its use expanded.

Phase-vanishing reactions are triphasic reactions that involve a reagent, a liquid perfluoroalkane, and a substrate. In a phase-vanishing reaction with PTFE (polytetrafluoroethylene) tape as the phase screen instead of a liquid perfluoroalkane, there is no limitation related to the density of a phase, and the denser phase can be in the top layer. Additionally, PTFE tape is inexpensive, easy to use, and reusable. In this work we qualitatively described PTFE tape's thickness, stretching characteristics, and permeability. We investigated the phase-vanishing PTFE method's usefulness both in known transformations and also in a novel nucleophile-assisting leaving group (NALG) reaction with menthol, thionyl bromide, and zirconium(IV) chloride. We successfully used PTFE tape as a phase screen in bromination, bromolactonization, esterification, chemiluminescence, and tandem bromination/esterification phase-vanishing reactions. We found that the PTFE tape is an effective phase screen and useful in performing a slow addition of a reagent.