Complex conformal rescalings and complex Lorentz transformations

Complex Lorentz transformations and complex conformal rescalings with independent conformal factors and are investigated in terms of elements of the group GL(2,C) G (2,C). It is shown how a general element of this group decomposes into a standard conformal rescaling (with =), a pure spin transformation, complex null rotations, and a complex boost-rotation. Of particular interest are the pure spin transformations that leave invariant the metric but transform the permutation spinors. It is these transformations that, when , are responsible for seemingly complicating the transformation law of the derivative operator and of spinors dependent thereon. It has been suggested that to avoid this complication one should allow the rescaled metric to have torsion. It is argued here that simplicity can be achieved even when the torsion-free condition is imposed.     

Effect of grafted methyl methacrylate on the catalytic hydrogenation of natural rubber

The graft copolymerization of methyl methacrylate onto natural rubber was carried out by using a cumene hydroperoxide redox initiator. The graft copolymer was purified by extraction and then hydrogenated in the presence of OsHCl(CO)(O₂)(PCy₃)₂. The graft copolymer and hydrogenated product were characterized by proton nuclear magnetic resonance (¹H NMR). The rate of hydrogenation was investigated using a gas-uptake apparatus. The hydrogenation was observed to be inverse first-order with respect to rubber concentration. The addition of a small amount of poly(methyl methacrylate) demonstrated a beneficial effect on the hydrogenation of the grafted copolymer.     

Bestimmung der Hexabromidzahl, insbesondere des Lein?ls

Ohne Zusammenfassung     

Zur Bestimmung des Mangans in Eisen und Stahl

Ohne Zusammenfassung     

Zur Bestimmung des Gerbstoffs

Ohne Zusammenfassung     

Zur Untersuchung der Gerbstoffe, bezw. des Leders

Ohne Zusammenfassung     

A faux hawk fullerene with PCBM-like properties

Reaction of C₆₀, C₆F₅CF₂I, and SnH(n-Bu)₃ produced, among other unidentified fullerene derivatives, the two new compounds 1,9-C₆₀(CF₂C₆F₅)H (1) and 1,9-C₆₀(cyclo-CF₂(2-C₆F₄)) (2). The highest isolated yield of 1 was 35% based on C₆₀. Depending on the reaction conditions, the relative amounts of 1 and 2 generated in situ were as high as 85% and 71%, respectively, based on HPLC peak integration and summing over all fullerene species present other than unreacted C₆₀. Compound 1 is thermally stable in 1,2-dichlorobenzene (oDCB) at 160 °C but was rapidly converted to 2 upon addition of Sn₂(n-Bu)₆ at this temperature. In contrast, complete conversion of 1 to 2 occurred within minutes, or hours, at 25 °C in 90/10 (v/v) PhCN/C₆D₆ by addition of stoichiometric, or sub-stoichiometric, amounts of proton sponge (PS) or cobaltocene (CoCp₂). DFT calculations indicate that when 1 is deprotonated, the anion C₆₀(CF₂C₆F₅)^– can undergo facile intramolecular S_NAr annulation to form 2 with concomitant loss of F^–. To our knowledge this is the first observation of a fullerene-cage carbanion acting as an S_NAr nucleophile towards an aromatic C–F bond. The gas-phase electron affinity (EA) of 2 was determined to be 2.805(10) eV by low-temperature PES, higher by 0.12(1) eV than the EA of C₆₀ and higher by 0.18(1) eV than the EA of phenyl-C₆₁-butyric acid methyl ester (PCBM). In contrast, the relative E _1/2(0/–) values of 2 and C₆₀, –0.01(1) and 0.00(1) V, respectively, are virtually the same (on this scale, and under the same conditions, the E _1/2(0/–) of PCBM is –0.09 V). Time-resolved microwave conductivity charge-carrier yield × mobility values for organic photovoltaic active-layer-type blends of 2 and poly-3-hexylthiophene (P3HT) were comparable to those for equimolar blends of PCBM and P3HT. The structure of solvent-free crystals of 2 was determined by single-crystal X-ray diffraction. The number of nearest-neighbor fullerene–fullerene interactions with centroid···centroid (⊙···⊙) distances of ≤10.34 Å is significantly greater, and the average ⊙···⊙ distance is shorter, for 2 (10 nearest neighbors; ave. ⊙···⊙ distance = 10.09 Å) than for solvent-free crystals of PCBM (7 nearest neighbors; ave. ⊙···⊙ distance = 10.17 Å). Finally, the thermal stability of 2 was found to be far greater than that of PCBM.