A one-pot stereoselective synthesis of novel polyfunctionalized imidazolidines

A facile, one-pot stereoselective synthesis of novel trans-4,5-dihydroxy-2-aryl-1,3-bis(heteroaryl)imidazolidines is achieved by a cyclocondensation reaction of 2 equiv of heteroarylamines with benzaldehyde derivatives, in the presence of guanidinium chloride as a polyfunctional organocatalyst, with aqueous glyoxal to afford the title products. This general protocol provides a wide range of new polyfunctionalized imidazolidines in good to high yields.     

One‐step Hydrothermal Synthesis and Assembly of Copper and Silver Nanoparticles to Aggregates in Glyoxal Reduction System

A simple hydrothermal process has been developed for the synthesis and assembly of copper and silver nanoparticles to aggregates. The reduction of Cu²⁺ and Ag⁺ ions to the zerovalent metal was performed by glyoxal in the absence of any external agent. The produced glyoxylic acid (GA) in the redox process stabi‐ lized metallic copper and silver particles and rendered them oxidation resistant for several months and dispersible in polar organic solvents and water. Detailed nanostructures of synthesized products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The results demonstrated that assembly of nanoparticles to aggregates and their regularity were dependent on the reaction conditions such as temperature and concentration of the starting material. The Ostwald ripening process was proposed to explain the formation of copper nanoparticles by TEM observation at several times during the reaction. The existence of the surface stabilizing agent was identified by Fourier Transform infrared spectroscopy (FT‐IR) and thermogravimetric analyses (TGA).     

Theoretical Studies on Mechanism and Rate Constant of Gas Phase Hydrolysis of Glyoxal Catalyzed by Sulfuric Acid

The gas phase hydration of glyoxal (HCOCHO) in the presence of sulfuric acid (H2SO4) were studied by the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST). The mechanism and rate constant of the ve di erent reaction paths are consid-ered corresponding to HCOCHO+H₂O, HCOCHO+H₂O H₂O, HCOCHO H₂O+H₂O, HCOCHO+H₂O H₂SO₄ and HCOCHO H₂O+H₂SO₄. Results show that H₂SO₄ has a strong catalytic ability, which can signi cantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD(T)/6-311++G(3df, 3pd)//M06-2X/6-311++G(3df, 3pd) level of theory. The rate constant of the H₂SO₄ catalyzed hydrolysis of glyoxal is 1.34×10^-11cm³/(molecule s), about 10¹³ higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10^-11cm³/(molecule s) at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H₂SO₄ catalyst is feasible and could compete with the reaction glyoxal+OH under certain atmospheric condi-tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer     

Flame-retardant effect of a functional DOPO-based compound on lignin-based epoxy resins

A simple and environmentally benign synthetic route to lignin-based epoxy resins is highly desirable. Alkali lignin and glyoxal are promising renewable and sustainable alternatives to phenol and formaldehyde, respectively. Their use is demonstrated to produce lignin-phenol-glyoxal novolac epoxy resins (LPG-NERs) through a simple one-pot synthesis. Flame retardancy of LPG-NERs was improved by functionalization with a N, S modified 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) material (termed DBS) obtained via nucleophilic reaction between DOPO and a N, S containing intermediate. FTIR and ¹H NMR analyses confirmed the successful fabrication of LPG-NERs and SBD. The introduction of lignin and SBD reduced crosslinking of the epoxy network, weakening mechanical properties, but conferred excellent flame retardancy (including vapor and condensed phases) as determined by LOI (34.5%), UL-94 (V-0 rating), and cone calorimetry tests (lower heat release and smoke production, and higher char formation). The SBD structure imparted a desirable vapor mechanism (blowing out phenomenon caused by the fire quenching effect of PO?/PO₂? radicals and dilution effect from non-condensable gases such as NH₃, N₂, SO₂), while lignin (a natural biochar precursor) in synergy with SBD imparted superior charring performance.     

乙二醛在Ti/纳米TiO2-Pt修饰电极上的电催化氧化

采用溶胶-凝胶和电沉积法制备Ti基纳米TiO2-Pt(Ti/纳米TiO2-Pt)修饰电极. X射线衍射(XRD)表明纳米TiO2为锐钛矿型, 扫描电镜(SEM)显示Pt纳米粒子在纳米TiO2多孔膜的表面呈现簇分散状态, 平均粒径约25 nm. 通过循环伏安(CV)和计时电流法研究了Ti/纳米TiO2-Pt修饰电极对乙二醛直接电氧化的电催化活性, 结果表明, 修饰电极对乙二醛的直接电氧化呈现良好的催化活性, 在0.60和1.23 V(vs SCE)出现两个氧化峰, 二者电流密度分别为16 和42 mA·cm-2, 约为纯Pt电极的2倍和1.5倍, 反应过程受浓差扩散控制.     

Kinetic Studies of Chromic Acid Oxidation of Glyoxal

The kinetics of chromic acid oxidation of glyoxal is reported. The reaction is first-order in glyoxal and indicates a gradual change from a first-order to a zero-order dependence on acidity. The kinetic nature of this reaction has been studied and the rate law is consistent with a proposed mechanism as follows; rate = kK_b, K[Cr⁺⁶][Gx][H⁺]/(l+0.238[H⁺]) at 25°C. The product analysis indicates that formic acid is the oxidation product under similar kinetic condition.     

Chromium(III) ion selective electrode based on glyoxal bis(2-hydroxyanil)

A poly(vinyl chloride) membrane based on glyoxal bis(2-hydroxyanil) as membrane carrier was prepared and investigated as a Cr(III)-selective electrode. The electrode has a linear dynamic range of 3.0×10⁻⁶-1.0×10⁻² mol l⁻¹, with a Nernstian slope of 19.8±0.5 mV per decade and a detection limit of 6.3×10⁻⁷ mol l⁻¹. It has a fast response time of <20 s and can be used for at least 3 months without any considerable divergence in potential. The proposed electrode revealed good sensitivities for Cr(III) over a wide variety of metal ions and could be used in a pH range of 2.7-6.5. Above all, the membrane sensor has been used very successfully for the analysis of some food materials and alloys for the determination of Cr(III) ion.     

A quantum-mechanical study of the interaction of glyoxal with guanine

A quantum molecular study by the SCFab initio method of the interaction of glyoxal with guanine provides for the formation of a stable covalent adduct in which the glyoxal fragment forms a complementary cyclic ring attached to the imino N₁ and amino N₂ atoms of guanine with the concomitant migration of the N-bonded H atoms to the oxygens of glyoxal. The reaction should proceed in two steps. The most plausible mechanism involves as the first step the interaction of a carbonyl group of glyoxal with the amino group of guanine followed by a similar interaction at the imino group of guanine, rather than the reverse order of interactions. The respective energy barriers are 49.7 and 63.9 kcal/mole. The intermediate product is also more stable when the adduct occurs first at N₂:30.7 kcal/mole versus 17.9 kcal/mole for the adduct at N₁.     

紫外分光光度法测定乙二醛含量的研究

首次报道利用醛基的成肟反应以及乙二醛二肟对紫外光的特征吸收，用紫外分光光度法测定乙二醛的含量。试验表明，在８．２×１０＾－６－５．９×１０＾－５ｍｏｌ／Ｌ浓度范围内，乙二醛溶液遵守Ｂｅｅｒ定律；方法的平均回收率为１００．７％（ｎ＝９，ＲＳＤ＝１．１％），具有简便，快速等优点。可供乙二醇氧化制备乙二醛研究中测定乙二醛产率用，也可用于乙二醛产品纯度的测定。     

KMnO4-乙二醛化学发光体系测定阿魏酸

酸性介质下,KMnO4氧化阿魏酸产生化学发光,乙二醛对该体系有增敏作用。结合流动注射技术,建立了测定阿魏酸的流动注射化学发光新方法。该方法线性范围为1.0×10-7～2.0×10-5mol/L,检出限为1.0×10-8mol/L,对1.0×10-6mol/L的阿魏酸平行测定11次,相对标准偏差为2.8%。该法用于太太美容口服液中阿魏酸的测定,结果令人满意。