Trifluoroethenylzinc reagent [CF(2)=CFZnX] was generated from the readily available halocarbon HFC-134a by an in situ metalation-transmetalation procedure at temperatures near to room temperature (15-20 degrees C). By systematic standardization of the metalation experiments by manipulation of solvent, cosolvent, temperature, zinc salt, and the base, the trifluoroethenylzinc reagent was produced in 73% yield at 20 degrees C in THF medium. The palladium-catalyzed cross-coupling reaction of the trifluoroethenylzinc reagent with various aryl iodides was carried out under mild reaction conditions to produce 1,2,2-trifluorostyrenes in 59-86% isolated yields. The stability of the intermediate trifluoroethenyllithium reagent was compared at different temperatures and solvent systems. Experimental evidence for the mono-anion from HFC-134a (CF(3)CHF(-)) was obtained by the trapping of the mono-anion with zinc halide in THF/TMEDA medium. The structure and complexation of both the mono- and bis-trifluoroethenylzinc reagents with TMEDA and other ligands are discussed.
A method is presented for determining the dynamic contact angle at the three-phase contact between a solid, a liquid, and a vapor under an applied force, using molecular simulation. The method is demonstrated using a Lennard-Jones fluid in contact with a cylindrical shell of the fcc Lennard-Jones solid. Advancing and receding contact angles and the contact angle hysteresis are reported for the first time by this approach. The increase in force required to wet fully an array of solid cylinders (robustness) with decreasing separation distance between cylinders is evaluated. The dynamic contact angle is characterized by partial slipping of the three phase contact line when a force is applied.
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