Novel pi-expanded radialene macrocycles with inner cavity

[structure: see text] Polyenyne macrocycles with pi-extended [9]- and [12]radialene frameworks have been synthesized. These radialenes exhibit restricted rotation of the aromatic rings, and the D3- and D4-symmetric structures in solutions have been determined by dynamic NMR. The macrocyclic radialenes bear small to medium inner cavities, and the small cavity of the pi-extended [9]radialene can incorporate a silver cation.     

Rotational power loss of magnetic steel sheets in a circular rotational magnetic field in CCW/CW directions

This paper presents rotational power loss properties of magnetic steel sheets under high flux density conditions using two-dimensional vector magnetic properties measurement. Recently it was reported by some research groups that the magnetic power loss measured in a counter clockwise (CCW) rotating field differed from that in a clockwise (CW) rotating field. This phenomenon was only observed in case of higher magnetic flux density excitation condition. We call this the CCW/CW problem. To clarify the reasons why the disagreement exists in the CCW/CW direction, we have examined angle errors of H- and B-coils by using geometrical, optical and magnetic methods. Then we compensated the measured vector components including different signals due to the angle errors. In the components of irremovable small angle error, we have also used the measured field strength waveforms in CCW/CW conditions. We have applied the compensation method to measurement of a grain-oriented electrical steel sheet.     

A measurement method of the magnetic properties of magnetic sheet by means of a single sheet tester at audio frequency

A single sheet tester (SST) for audio frequency of 400 Hz–10 kHz was made experimentally and the magnetizing winding can get the nearly uniform distribution of flux density of a specimen in the longitudinal direction at the frequency up to 10 kHz. The flux densities at various positions of strips measured by the Epstein method were detected by search coils wound on strips at 400 Hz and 1.0 T. They have large discrepancy. However, the magnetic properties obtained from both methods have a little discrepancy. Although the uniformity of flux distribution in the Epstein frame is not sufficient, the average is fairly effective because the magnetic properties can be assumed to be locally linear within the small deviation of flux density.     

Polymerization of Methyl Methacrylate Initiated with Organomanganate Reagents

Organomanganate reagents [R₃Mn]^–Li⁺ (R = Bu, Me) were found to polymerize methyl methacrylate in the presence of potassium tert‐butylate. A conversion of the tacticity of the resulting poly(methyl methacrylate)s from heterotactic (mr = 54%) to isotactic (mm = 58%) was observed upon changing the R group of the initiator from Bu to Me. The addition of triisobutylaluminium was found to efficiently control M̄_w and M̄_w/M̄_n of the resulting polymers.     

Color‐Tunable Solid‐State Fluorescence Emission from Carbazole‐Based BODIPYs

Several carbazole‐based boron dipyrromethene (BODIPY) dyes were synthesized by organometallic approaches. Thiazole, benzothiazole, imidazole, benzimidazole, triazole, and indolone substituents were introduced at the 1‐position of the carbazole moiety, and boron complexation of each dipyrrin generated the corresponding compounds 1 , 2 a , and 3 – 6 . The properties of these products were investigated by UV/Vis and fluorescence spectroscopy, cyclic voltammetry, X‐ray crystallography, and DFT calculations. These compounds exhibited large Stokes shifts, and compounds 1 , 2 a , and 3 – 5 fluoresced both in solution and in the solid state. Complex 2 a showed the highest fluorescence quantum yield (Φ_F) in the solid state, therefore boron complexes of the carbazole–benzothiazole hybrids 2 b – f , which had several different substituents, were prepared and the effects of the substituents on the photophysical properties of the compounds were examined. The fluorescence properties showed good correlation with the results of crystal‐packing analyses, and the dyes exhibited color‐tunable solid‐state fluorescence.     

Thermal decomposition of biodiesel fuels produced from rapeseed, jatropha, and coffee oils with different alcohols

Thermal behaviors and the effects of various alcohols on biodiesel fuel (BDF) derived from edible oil such as rapeseed oil and inedible oils such as coffee oil and jatropha oil, were studied. TG curves in air and N₂ of rapeseed BDF, jatropha BDF, drip coffee, and BDF espresso coffee BDF synthesized from the methanol presented similar results which exhibited only one mass loss step, which is attributed to vaporization or combustion of the methyl esters. The decomposition temperature (T _d) of rapeseed, jatropha and coffee Bt-BDF were high by about 30 °C compared with the standard, Me-BDF. The amount of decomposition residue at 400 °C was found to be related to the number of carbon atoms in the alcohol, with the residue becoming greater with more carbons in the alcohol. The oxidation stability of rapeseed BDF depended on the carbon chain of the alcohol. However, coffee and jatropha BDFs were stable in spite of the long chain alcohol.     

Anionic polymerization of methyl methacrylate initiated with late transition‐metal halides/organolithium/triisobutylaluminum systems

Anionic polymerization of methyl methacrylate (MMA) initiated with late transition‐metal halides [manganese chloride (MnCl₂), iron dichloride (FeCl₂), iron trichloride (FeCl₃), cobalt chloride (CoCl₂), or nickel bromide (NiBr₂)]/organolithium [nButyllithium (nBuLi) or phenyllithium (PhLi)]/triisobutylaluminum (iBu₃Al) systems is described. Except for the system with NiBr₂, the polymerizations of MMA afforded narrow molecular weight distribution poly(methyl methacrylate)s (PMMAs) with high molecular weights in quantitative yields at 0 °C in toluene. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses of the PMMAs obtained by the systems with FeCl₂, FeCl₃, and CoCl₂ revealed that the polymers had hydrogen (H) at both chain ends. Accordingly, the reaction of the transition‐metal halides with the organolithium in the presence of iBu₃Al should result in the formation of transition‐metal hydride [M‐H]^? species, which was nucleophilic enough to initiate the MMA polymerization. Because the presence of a six‐membered cyclic structure resulting from backbiting was confirmed from the MALDI‐TOF MS analyses of the PMMA obtained with the metal halide (FeCl₂, FeCl₃, or CoCl₂)/organolithium systems in the absence of iBu₃Al, the introduction of H at the ω‐chain end indicated that iBu₃Al should prevent the backbiting. However, the MnCl₂/nBuLi/iBu₃Al initiating system gave PMMAs bearing H at the α chain end and six‐membered cyclic structure at the ω chain end. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1962–1977, 2003     

The flash points and thermal behaviors of diesel blends with biodiesels, α-pinene,d-limonene and caffeic acid as antioxidants

The present study assessed the effects of antioxidants on the flash point and thermal behavior of diesel fuel blended with 3–10 vol% biodiesel made from spent coffee grounds oil (SCGO) or Jatropha seed oil (JSO) extracted using with n-hexane or acetone, with or without α-pinene and d-limonene (as volatile antioxidants) or caffeic acid (as a non-volatile antioxidant). Effects were evaluated by assessing flash points and by thermogravimetry/differential thermogravimetry and differential thermal analysis (DTA). The flash points of the JSO and SCGO biodiesels obtained from oils extracted using n-hexane were higher than those extracted using acetone, and the addition of 10 vol% JSO or SCGO biodiesel made using acetone extraction increased the flash point by up to 2 °C. The DTA results for JSO and SCGO biodiesels also changed according to the extraction solvent. The flash points of diesel/α-pinene/d-limonene mixtures decreased as the amount of α-pinene was increased up to 10 vol%. TG peaks obtained from 10% α-pinene/d-limonene (50 vol%/50 vol%) in diesel were lowered by approximately 20 °C. The addition of 100–1000 mg kg^?1 caffeic acid to diesel lowered the flash point by 2 °C and shifted the TG peak to approximately 75 °C from the value of 66 °C for pure diesel. This effect was constant regardless of the caffeic acid content, while DTA results were largely unaffected by this additive. The results of this work confirm that both flash point and thermal behavior are dependent on the particular type of antioxidant employed.

     

Diphenylparabanic acid as a synthon for the synthesis of α-diketones and α-ketocarboxylic acids

Diphenylparabanic acid was found to react with >2 equiv of organolithiums at -78 °C to effectively give the corresponding symmetrical α-diketones. However, upon treatment with 1 equiv of organolithium, the parabanic acid gave mainly 5-substituted 5-hydroxyimidazolidine-2,4-diones. On the other hand, Grignard reagents were less reactive toward the parabanic acid at low temperature, and selectively gave the corresponding 5-hydroxyimidazolidine-2,4-diones even if more than 1 equiv of the reagents was used. A tandem process in which the parabanic acid was first reacted with a Grignard reagent and then reacted in one-pot with an organolithium effectively gave the unsymmetrical α-diketone. 5-Substituted 5-hydroxyimidazolidine-2,4-diones were useful as versatile precursors for preparing α-ketocarboxylic acids as well as unsymmetrical α-diketones.