Kinetic and mechanistic studies of the copolymerization of bis-4-substituted-1,2,4-triazoline-3,5-diones with styrenes

Highly reactive 4-substituted-1,2,4-triazoline-3,5-diones (TDs) have been studied extensively as dienophiles, but little work has been done on their role as enophiles and particularly on their use as propagating species in polymerization studies. The copolymerization between bis-4-substituted-1,2,4-triazoline-3,5-diones (bis-TDs) and styrene has been reported. The purpose of the present work was to synthesize new copolymers derived from a variety of substituted styrenes and bis-TDs and to study the mechanism and kinetics of this novel polymerization. Three bis-TDs were prepared: 3,3′-dimethyl-4,4′-bis[3,5-dioxo-1,2,4-triazoline-4-yl] biphenyl (8), t-1,4-bis[3,5-dioxo-1,2,4-triazoline-4-yl] methyl cyclohexane (9), and 4,4′-bis[3,5-dioxo-1,2,4-triazoline-4-yl] phenyl ether (10). Their structures were fully established by spectroscopic studies, elemental analyses, and indirectly, their quantitative ene reactions with 2,3-dimethyl-2-butene. Copolymerization between bis-TDs and substituted styrenes was carried out in dimethylformamide (DMF), tetrahydrofuran (THF), or dichloroethane (DCE). Polymers formed were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and viscometry. Molecular weights of polymers range from 5000 to 16,000 in most cases. They were stable up to 250°C and higher. Polymers derived from bis-TDs and p-t-butylstyrene, α-methylstyrene, p-nitrostyrene, and p-acetoxystyrene contained only Diels-Alder-ene (DAe) repeating units, whereas those derived from styrene, p-chlorostyrene, p-bromostyrene, p-methylstyrene, p-methoxystyrene, and 4-vinylbiphenyl contained both DAe and double Diels-Alder (dDA) repeating units. A kinetic study of the copolymerization of 4,4′-bis-(3,5-dioxo-1,2,4-triazoline-4-yl) phenyl ether with α-methylstyrene, p-t-butylstyrene, styrene, p-chlorostyrene, and p-nitrostyrene in DCE was carried out; the copolymerization rate constants were 60.9, 49.8, 8.4, 5.5, and 0.8 (1 mol^?1s), respectively.     

Novel construction of the brassinolide side chain

A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described.     

Electronic density of levels in a disordered system

Three-, two-, and one-dimensional disordered systems with randomly distributed, purely repulsive scattering centers, known as Lorentz models, are studied in the low energy limit [1]. Using a functional integral representation and a version of the “replica trick”, we have found in the D-dimensional system the density of electronic levels of the form

$\text{n(E)=b}{}_0\text{Eγ}\text{exp}\text{(?b}{}_1\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>D</mtext><mtext>2</mtext><mtext>)</mtext>}}\text{+b}{}_2\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>D</mtext><mtext>2</mtext><mtext>)+1</mtext>}}\text{+·+b}{}_{\mathrm{D}}\text{E}{}^{\mathrm{<mtext>?(</mtext><mtext>1</mtext><mtext>2</mtext><mtext>)</mtext>}}\text{)(1+O(}\text{E}\text{))}$

and the constants b₀, b₁,…, b_D, and γ have been determined.     

Polarographic Behaviour and Determination of Kinetic Parameters of Lead-Pamoate Complex in Dimethyl Sulfoxide

The polarography of lead ion in dimethyl sulfoxide (DMSO) was investigated in the DMSO concentration range 0–80 vol.%. The complex species identified were Pb₂(DMSO)⁴⁺₃, Pb(DMSO)²⁺₃ and Pb(DMSO)²⁺₆ in [DMSO]<10 vol.%, 10< [DMSO]<43 vol.% and [DMSO]>43 vol.%, respectively. In the presence of pamoic acid, the reduction of lead ion in DMSO was two-electron reversible diffusion-controlled at pH≤6.0, but it became irreversible at pH>6.0. The complex species identified was Pb(D_m)₂(P_m)₃(OH)^6? at pH>6.0. The rate constants of electro-reduction and electro-oxidation, activation energies were determined. The hydrolysis constants of lead ion in dimethyl sulfoxide concentration 40–70 vol.% at pH 4.5–6.0 were found to be of the order of 10^?6. The stability constants of the Pb(DMSO)²⁺₃ and Pb(DMSO)²⁺₀ were also determined to be of the orders of 10¹ and 10⁵, respectively.     

羟乙基皂仁胶水溶胶和凝胶体系流变性的研究——不含交联剂溶胶体系的粘度

研究了羟乙基皂仁胶水溶胶体系的粘度对浓度、温度和切变速率的依赖性。溶胶的表观粘度进行了非牛顿校正,其表观粘度的切变速率依赖性可用幂律模型描述。采用Spencer-Dillon方程求得的体系零切粘度与浓度的关系可用Onogi公式描述。对于溶剂和较稀溶液,温度对粘度的影响可用Andrade公式描述,但对较浓溶液,此式不再适用。     

Sorption and desorption of neptunium(V) on calcareous soil and its solid components: A comparative study

The sorption and desorption isotherms of untreated calcareous soil and three treated soils to remove CaCO₃, organic matter (OM) and both CaCO₃ and OM were determined and analyzed with the Freundlich equation at pH 7.8, moderate concentrations of NpO₂ ⁺ (~10^-5mol/l), in the presence of 0.01 mol/l CaCl₂ and under ambient aerobic conditions. The relative contribution of CaCO₃ and OM to the neptunium(V) sorption on calcareous soil and the sorption/desorption hysteresis is discussed. The effects of adding fulvic acid (FA) and carbonate in to the solution on the sorption of neptunium(V) on the soils were also studied. The sorption and desorption characteristics of NpO₂ ⁺, Zn²⁺, Sr²⁺ and Cs⁺ on the soils are compared.     

VIB金属蝎型配合物(Scorpionate)的研究进展

综述了VIB金属(Mo、W)多吡唑硼配合物近年来的研究进展。详细地叙述了第二代多吡唑硼配体的合成与表征。     

A Substituted Tetraazaporphyrinogen as an Electroactive Component for a Polymeric Membrane Anion-Selective Electrode

A novel anion-selective electrode has been prepared by usingtetraazaporphyrinogen as the electroactive component and o-nitrophenyloctylether as the plasticizer. The electrode exhibits almost Nernstian responsecharacteristics for Pic^-, ReO ₄ ^- ,SCN^-, ClO ₄ ^- and TPB^-. The linearresponse ranges towards the above-mentioned anions are 10^-6 10^-2, 10^-5 10^-2,10^-5 10^-2, 10^-5 10^-1, and 10^-5 10^-2mol/Land the corresponding slopes are -56.8, -57.1, -56.3, -56.1, and -59.9mV/decade with correlation coefficients of -0.99978, -0.99987, -0.99999,-0.99998, and -0.99998, respectively. The electrode shows an anti-Hofmeisterselectivity sequence: Pic^- > SCN^- >ReO ₄ ^- > ClO ₄ ^- > I^- >Br^- > BF ₄ ^- > Sal^->NO ₃ ^- > Cl^-. The unusual responsemechanism of the novel anion-selective electrode was investigated byexperimental observations and calculation with the MNDO method. Theelectrode was used as a TPB^- and a Pic^-sensitiveelectrode, respectively, and applied to the assay of levamisolehydrochloride tablets by potentiometric titration and Gran's methods. Theresults obtained are in excellent agreement with that determined by thestandard pharmacopoeia method based on nonaqueous titration.