Addition of thianthrene cation radical to non-conjugated dienes—Part I: Addition to one double bond

Reaction of thianthrene cation radical tetrafluoroborate and hexafluorophosphate with an excess of 1,4-hexadiene, 1,5-hexadiene, 1,7-octadiene, 1,8-nonadiene and 1,9-decadiene gave, in each case, a mixture of bis- and monoadduct from addition to one of the diene’s double bonds. Addition to both double bonds did not occur. The monoadduct of each diene and the bisadduct (7a) of 1,5-hexadiene were isolated. All monoadducts and 7a were characterized with ¹H and ¹³C NMR spectroscopy. By reaction on activated alumina adducts were converted into (E)- and (Z)-(5-thianthreniumyl)dienes, all of which were characterized with ¹H and ¹³C NMR spectroscopy. The monoadduct (6a) of 1,4-hexadiene and the bisadduct 7a were characterized with X-ray crystallography.     

Synthesis of cyclic poly(methyl methacrylate) by the intramolecular cyclization of α-amino, ω-carboxyl heterodifunctional poly(methyl methacrylate)

Summary α-Amino, ω-carboxyl heterodifunctional poly(methyl methacrylate) was prepared by a living anionic polymerization of methyl methacrylate using N,N'-diphenylethylenediamine monolithium amide and succinic anhydride as an initiator and terminator, respectively. Its intramolecular cyclization was carried out to obtain a well-defined cyclic poly(methyl methacrylate). Received: 27 June 2001/Accepted: 16 July 2001     

Formation of Hydroperoxy-, Keto- and Hydroxy-Dienes in FAME from Oils: Influence of Temperature and Addition of α-Tocopherol

The influence of temperature (40, 60 and 80 °C) and addition of α-tocopherol (0, 500 mg/kg) on the formation and distribution of the main oxidation products of linoleic acid, i.e. hydroperoxy-, keto- and hydroxy-dienes, were studied in samples of fatty acid methyl esters (FAME) derived from high-linoleic (HL) and high-oleic (HO) sunflower oils. In the range of temperatures studied, the formation of hydroperoxydienes showed monomolecular and bimolecular rate constants that ranged from 0.01 to 1 mmol^1/2kg^−1/2h⁻¹ and from 0.02 to 0.9 h⁻¹, respectively. The overall activation energies involved were similar for both samples and for the monomolecular and bimolecular periods (63–68 kJ/mol). The relative oxidation of methyl linoleate, which depended on the fatty acid composition of the FAME sample, was unaffected by temperature. At the three temperatures assayed, hydroperoxydienes constituted approximately 90 and 50% of total hydroperoxides in the HL and HO samples, respectively. Formation of keto- and hydroxy-dienes was influenced by temperature in a similar way to hydroperoxydienes and, consequently, changes in the distribution of compounds were not observed. The addition of α-tocopherol not only decreased the overall oxidation rate, but also affected the distribution of compounds. The content of hydroperoxydienes relative to that of total hydroperoxides was not affected by the presence of the antioxidant in the HL sample, whereas a significant increase (75%) was found in the HO sample compared with the control (50%). The addition of α-tocopherol in both samples also resulted in a slight increase of keto- and hydroxy-dienes in relation to hydroperoxydienes.     

Synthesis and characterization of novel crown ether containg copolymers Ru catalyzed copolymerization of 4′-acetylbenzocrown ethers with α,ω-dienes

Summary Ruthenium catalyzed step growth copolymerization of 4-acetylbenzo-15-crown-5 and 4-acetylbenzo-18-crown-6 and ,-dienes such as 1,3-divinyltetramethyldisiloxane or 3,3,6,6-tetramethyl-3,6-disila-1,7-octadiene give novel copolymers which incorporate crown ethers into the polymer backbone in a regular manner. The synthesis of these thermally stable copolymers and their characterization is reported. Lithium cation crown complexes have been formed.     

Free radical polymerization of ethyl methacrylate and ethyl α-hydroxy methacrylate: A computational approach to the propagation kinetics

The propagation kinetics of ethyl methacrylate (EMA) and ethyl α-hydroxy methacrylate (EHMA) has been subject to a computational study to understand their free radical polymerization (FRP) behavior in bulk and in solution using Density Functional Theory (DFT). The propagation of EHMA is studied in ethanol and toluene to assess the effect of hydrogen-bonding solvents on FRP of monomers with α-hydroxy functionality. Although EMA and EHMA resemble each other in structure, EHMA propagates faster in bulk due to the presence of intermolecular hydrogen-bonds, which tend to facilitate the approach of the propagating species. This falls in contrast with the experimentally observed lower propagation rates of EHMA in ethanol compared to toluene. Calculations show that the 2.28 rate acceleration in toluene is governed by the ratio of the pre-exponential factors, which reflect the entropies of activation, in both media. The polar protic solvent ethanol has a disruptive effect via hydrogen-bonding on the 6-membered ring shape of EHMA monomers thus decreasing the entropy of activation of the reaction. In the case of toluene, there are no special interactions with the hydrophobic solvent, the entropy of activation is higher than in ethanol.     

Cyclopolymerization. Part XXXII radical polymerization of α-(2-phenylallyloxy)methylstyrene: synthesis of highly cyclized polymers with high glass transition temperatures and thermal stability

A new 1,6-diene, α-(2-phenylallyloxy)methylstyrene (1), was synthesized and its radical cyclopolymerizations were studied, since 1 is expected to yield highly cyclized polymers with thermal stability and high glass transition temperatures. A low homopolymerization tendency of the monofunctional counterpart of 1 can be assumed reasonably, because it is a derivative of α-methylstyrene with a low ceiling temperature. This means that intermolecular propagation leading to pendant unsaturations is hard to occur during the polymerization of 1, which results in the formation of highly cyclized polymers. In fact, the degree of cyclization of poly(1) obtained at 180 °C attained the value 99%. Structural studies using a monomeric cyclic compound obtained by the telomerization of 1 permitted to assign main repeating cyclic units of poly(1) to a six-membered ring. The poly(1)s with a higher degree of cyclization were found to be stable up to 300 °C on thermogravimetric analyses and their glass transition temperatures were detected at temperatures over 250 °C.     

Transformation of the Β-Triketone Pesticides Tembotrione and Sulcotrione by Reactions with Ozone: Kinetic Study,Transformation Products,Toxicity and Biodegradability

Rate constants between ozone and triketone herbicides, tembotrione and sulcotrione, were determined between pH 2 and 12. Both compounds are completely transformed within seconds by ozone under real water treatment conditions. A reaction pathway was proposed based on the identification of transformation products. Toxicity evaluation using Vibrio fischeri test showed that a residual toxicity remained even after degradation of the major by-products, but biodegradation significantly increased from 50% to 70% for molar ozone to pesticide ratios from 0 to 2. Thus, ozonation coupled with biological treatment would drastically reduce the risk associated to the presence of triketone herbicides.     

Titanium silicate molecular sieves (TS-1 and TS-2) catalyzed Michael reaction of silyl enol ethers with α,β unsaturated carbonyl compounds

The Michael addition reaction has been carried out with silyl enol ether and Michael acceptors such as acrylates, and , - unsaturated ketones over aluminum-free titanium silicates (TS-1 and TS-2) in the absence of H₂O₂. The reaction was carried out slightly above room temperature (40°C) in the presence of dry solvents giving moderate to good yield. The effect of various modified zeolites like RE-Y, La-Y, steamed-Y, Na-Y, VS-1, SnS-1, Zn/ZSM-5 and different solvents has been studied. The catalytic activity is explained on the basis of oxophilic Lewis acidity of titanium silicate molecular sieves.     

Spark plasma sintering of multi-cation doped (Yb,Sm) α/β-SiAlON ceramic tool materials: Effects of cation type,composition, and sintering temperature

The multi-cation doped α/β-SiAlON composite ceramics tool materials were prepared via spark plasma sintering. The effects of cation type (Yb, Sm, Yb/Sm), composition, and sintering temperature on densification behavior, phase formation, microstructural evolution, and mechanical properties of α/β-SiAlON were studied. Results showed that the addition of Sm₂O₃ in Yb/Sm-SiAlON could decline the shrinkage temperature and accelerate the densification process due to the increased liquid phase volume and decreased viscosity. The Sm₂O₃ played the role of both sintering additives and stabilizing cation of α-SiAlON, which could promote the formation of α-SiAlON and the elongation of β-SiAlON, thus acquired refined α grains and large aspect ratio of β grains. The SPS-sintered multi-cation doped Yb/Sm-SiAlON with 2 wt% additional Sm₂O₃ possessed excellent comprehensive mechanical properties (3.40 g/cm³, 18.53 ± 0.18 GPa, and 6.13 ± 0.23 MPa m^1/2).     

Reactions of Metal Ion Complexes with Lignin Model Compounds,Part III. Rh(TSPP) Catalyzed Formation of Guaiacol from β-Aryl Ethers in Exceptionally High Yield

Trisodium meso-tetra-4-sulfonatophenylporphinerhodium(III) (Rh(SPP)) was found to be a very effective catalyst for cleaving the β-aryl ether bonds of the lignin model compounds guaiacylglycol β-guaiacyl ether (1) and guaiacylglycerol β-guaiacyl ether (11). In both cases very large amounts of guaiacol (2) were formed regardless of whether the reducing sugar glucose was present or not. With the substituted phenylethane model 1 the other major product was acetovanillone (5); with the substituted phenylpropane model 11 considerable amounts of vanillin (4) were formed. The products obtained with the rhodium catalyst were very different to those formed in the Co(SPP) or anthraquinone (AQ) catalyzed reactions. They were, however, similar to those obtained with Fe(TSPc), although the rhodium catalyst was much more active and formed guaiacol at a much faster rate. In addition to these reactions, the rhodium complex also catalyzes the partial demethylation of the 3, 4-dimethoxyphenyl model compound 10. Mechanisms are proposed for these reactions in which the key steps involve single electron transfer between the catalyst and the substrate.     

Ionic solvation—III. free energies of transfer of copper(II) ion from water to sulfolane,tetrahydrofuran, acetone,dioxan and dimethylsulphoxide and to their mixtures with water

The emf of the cell: Cu/Cu²⁺, water + organic co-solvent/water, Cu²⁺//Cu with sulfolane, dioxan, tetrahydrofuran, acetone and dimethylsulphoxide (DMSO) as organic co-solvents has been measured for different solvent compositions. To decrease the liquid junction potential the salt bridge filled with the methanolic solution of tetrabutylammonium picrate has been applied. The emf data were used to calculate the Gibbs free energy of copper(II)cation transfer from water to nonaqueous or mixed solvents. Determined free energies of transfer are negative for DMSO and positive for other organic solvents.