Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland.
Published: October 2021
AI Article Synopsis
Article Abstract
We present and compare two high-pressure, high-repetition-rate electric-discharge sources for the generation of supersonic beams of fluorine radicals. The sources are based on dielectric-barrier-discharge (DBD) and plate-discharge units attached to a pulsed solenoid valve. The corrosion-resistant discharge sources were operated with fluorine gas seeded in helium up to backing pressures as high as 30 bars. We employed a (3 + 1) resonance-enhanced multiphoton ionization combined with velocity-map imaging for the optimization, characterization, and comparison of the fluorine beams. Additionally, universal femtosecond-laser-ionization detection was used for the characterization of the discharge sources at experimental repetition rates up to 200 Hz. Our results show that the plate discharge is more efficient in F dissociation than the DBD by a factor between 8 and 9, whereas the DBD produces internally colder fluorine radicals.
We have developed a glycosyl radical-based synthesis of -alkyl glycosides through a deoxygenative Giese addition-reduction-cyclization cascade, in which readily available 1-hydroxy carbohydrates serve as precursors for glycosyl radicals and aryl alkenes function as radical acceptors. This reaction not only provides an effective method for accessing a previously underexplored class of functionalized cyclopropanes but also enhances the application of Giese addition in the synthesis of -alkyl glycosides by derivatizing the radical intermediate generated through polar cyclization to yield a cyclopropane.
To provide fluorinated allylamines, a visible-light photocatalytic C-F/C-H coupling of easily accessible -difluoroalkenes and secondary -alkylanilines was described. The protocol proceeded under mild conditions, with excellent functional group compatibility and a broad scope including complex natural product derivatives, thus providing a green method for the preparation of high-value functionalized monofluoroalkenes. Mechanistic studies elucidated a photoredox catalyzed radical-radical coupling pathway.
Dimethyl sulfide (CHSCH) is the largest natural source of atmospheric sulfur. Bis(trifluoromethyl) sulfides (CFSCF) are one of the perfluorinated thioethers with great interest as the new refrigerant fluid and dielectric replacement gas for the sake of environmental concern. In order to clarify the effect of fluorine substitution, degradation mechanisms and kinetics for the reactions of CHSCH and CFSCF with OH radicals in the atmosphere have been calculated comprehensively in a comparative manner using various high-level methods.
Fluoride contamination is a serious environmental problem in lepidolite hydrometallurgy wastewater. The treatment of fluoride-bearing wastewater is challenging because of the presence of coexisting ions including lithium (Li), rubidium (Rb), silicate (SiO), sulfate radical (SO). However, aluminum-modified zeolite (Al@zeolite) with sufficient hydroxyl groups and high adaptability has unique advantages for eliminating fluoride from lepidolite hydrometallurgy wastewater.
The heme paradigm where Fe=O acts as the C-H oxidant and Fe-OH rebounds with the formed carbon-centered radical guides the design of the prototypical synthetic hydroxylation catalyst. We are exploring methods to evolve beyond the metal-oxo oxidant and hydroxide rebound, to incorporate a wider array of functional group. We have demonstrated the application of CoII(OTf)2 (10 mol% catalyst; OTf = trimfluoromethanesulfonate) in combination with polydentate N-donor ligands (e.
