Abstract:The proton mobilities (kinetic acidities) of bis-and tris(trifluoromethyl)benzene are dictated to a large extent by steric factors; the trifluoromethyl group is a fairly bulky substituent that can seriously impede the approach of the metalating reagent. Most satisfactory results in terms of yields and selectivities have been achieved with lithium 2,2,6,6-tetramethylpiperidide or with methyllithium in the presence of potassium tert-butoxide, a slim version of the standard superbase. The rates of deprotonation under irreversible conditions do not parallel the thermodynamic (equilibrium) acidities. Substituent effects on the deprotonation energies in the gas phase appear to be additive: each trifluoromethyl group lowers it by 13 kcal mol À1 when located ortho with respect to the carbanion, and by 10 kcal mol À1 when located in a meta or para position.
We present the results of a structural study of metallic alloy liquids from high temperature through the glass transition. We use high energy X-ray scattering and electro-static levitation in combination with molecular dynamics simulation and show that the height of the first peak of the structure function, S(Q) − 1, follows the Curie-Weiss law. The structural coherence length is proportional to the height of the first peak, and we suggest that its increase with cooling may be related to the rapid increase in viscosity. The Curie temperature is negative, implying an analogy with spin-glass. The Curie-Weiss behavior provides a pathway to an ideal glass state, a state with long-range correlation without lattice periodicity, which is characterized by highly diverse local structures, reminiscent of spin-glass.
Sodium dithionite-initiated reactions of pyrrole and 1methylpyrrole with 1-bromo-1-chloro-2,2,2-ethane in an acetonitrile-water mixture provide the respective 5-(trifluoromethyl)dipyrromethanes 1 and 3 as main products in 40-58% isolated yields and of high purity. Small amounts of tripyrranes 2 and 4 are also formed and could be isolated from the reaction mixtures. 1-Methyl-2,5-bis[2,2,2-trifluoro-1-(1-methyl-2-pyrrolo)ethyl]pyrrole (4) Mp 194-196 °C. EI-MS: m/z (%) = 403 (58, M + ), 334 [100, (M -CF 3 ) + ], 265 [33, (M -2CF 3 ) + ], 162 (8), 133 (26), 94 (15). Crystal Structure of 3 Molecular Formula: C 12 H 13 F 3 N 2 , F.W. = 242.24. X-Ray diffraction experiment was performed on a Nonius BV MACH3 diffractometer using graphite monochromatised CuKa radiation (l = 1.54178 Å). Lattice constants for compound 3 were determined by a least squares fit of the setting angles of 15 reflections: a = 8.8547(6), b = 8.5247(4), c = 15.4952(9) Å, b = 91.644(5) o , V = 1169.15(12) Å 3 , Z = 4, D c = 1.376 Mgm -3 , monoclinic space group P2 1 /n, F(000) = 504, absorption coefficient m(CuKa) = 1.002 mm -1 , crystal size 0.56´0.35´0.35 mm. 1632 Unique reflections have been masured in the q-range 5.69 to 73.97 o . These have been corrected for LP and y-scan based absorption (max. and min. transmission
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