V_2O_5/C催化氧化乙二醛制备乙醛酸

利用等体积浸渍法制备了V2O5/C催化剂,并应用于乙二醛的液相氧化反应,采用XRD、TEM手段对催化剂进行了物化性质表征.结果表明,V2O5/C对乙二醛的氧化表现出较高的催化活性和乙醛酸选择性,反应10h,乙二醛的转化率达29.2%,乙醛酸得率13.6%.与贵金属Pd-Bi/C催化剂相比,V2O5/C催化剂的稳定性和重复使用效果都比较好.     

Gem-dinitro compounds in organic synthesis. 4. Use of the condensation product of glyoxal and dinitromethane in the synthesis of nitro-1,2,3-triazoles

The condensation of dinitromethane with glyoxal has been investigated and it has been demonstrated that 1,1,4,4-tetranitro-2,3-butandiol, -hydroxy-,-dinitropropionic acid or their mixture may be formed. Interaction of 1,1,4,4-tetranitro-2,3-butandiol or 1,4-dibromo-1,1,4,4-tetranitro-2,3-butanediol diacetates with sodium azide leads to bis(5-nitro-1,2,3-triazol-4-yl) via intermediate 1,1,4,4-tetranitro-1,3-butadiene.For communication 3, see [1].N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2123–2131, September, 1992.     

Ag/ZrO2催化剂上的1,2-丙二醇选择性气相氧化反应

采用浸渍法制备了一系列Ag/ZrO₂催化剂, 考察了Ag/ZrO₂催化剂对1,2-丙二醇选择性氧化合成丙酮醛反应的催化性能. 实验结果表明: 在原料气配比为V(N₂)∶V(O₂)＝300∶19, n(O₂)/n(alcohol)＝1.2, 反应物液时空速为3.2 g/(g•h), 反应温度为673 K时, 1,2-丙二醇选择性氧化合成丙酮醛反应的转化率为95.7%, 选择性为55.3%, 高于传统电解银催化剂. UV-Vis DRS和XPS的研究结果表明: 在Ag/ZrO₂催化剂上存在大量的Ag^＋和Ag_n^δ＋有利于促进催化活性的提高.     

Four‐Component Cyclocondensation of Aminodiazines,Glyoxal, Formaldehyde,and Methanol to Imidazolidines

Four‐component reaction of aminodiazines (2‐aminopyrimidine and 2‐aminopyrazine), glyoxal, formaldehyde, and methanol yields trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrimidinyl)imidazolidine (5a) and trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrazinyl)imidazolidine (5b), respectively. Changing methanol to acetonitrile leads to the formation of the corresponding 1,3‐bis(2‐pyrimidinyl) and‐1,3‐bis(2‐pyrazinyl)‐ derivatives of trans‐4,5‐dihydroxyimidazolidine (6). Details of the proposed mechanism are discussed.     

金催化剂上乙二醛氧气氧化合成乙醛酸的研究

利用沉积-沉淀法和溶液相还原法制备了系列金催化剂,以氧气氧化乙二醛合成乙醛酸为探针反应,进行了反应条件的优化,并通过对催化剂进行XRD、AAS、UV-Vis和XPS表征,分析了影响催化剂活性的因素.结果显示:与沉积-沉淀法相比,采用溶液相还原法制备的催化剂Au/ZrO2(L),金的实际负载量较高,表现出较高的催化活性,当溶液pH为7.7,反应温度为323 K时,乙醛酸收率达到6.2%.     

Synthesis of new 3-cyanoacetamide pyrrole and 3-acetonitrile pyrrole derivatives

A new fused heterocyclic derivatives of pyrrole containing acetonitrile or cyanoacetonitrile moiety at 3-position is described by a one-pot multicomponent reaction. The reaction of dimedone, various aniline, aryl glyoxal with malononitrile/ethyl cyanoacetate/methyl cyanoacetate under mild conditions. The present method does not involve any hazardous organic solvents or catalysts. The significant features of this method are readily available starting materials, good yields, and easy purification.     

Preparation and characterization of a nanoscale poly(vinyl alcohol) fiber aggregate produced by an electrospinning method

Nanoscale poly(vinyl alcohol) (PVA) fiber (100–500 nm) aggregates were prepared with an electrospinning technique. Additionally, a chemical crosslinking method was used to crosslink the nanoscale PVA fiber aggregates. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and scanning electron microscopy techniques were employed to characterize the PVA fiber aggregates. The different crosslinking densities of the PVA fiber aggregates were obtained through the control of the weight percentage of glyoxal to PVA. The crosslinking densities due to heat treatment and chemical crosslinking were studied. The influence of heat treatment could be neglected in contrast to chemical crosslinking when the curing temperature was 120 °C. The primary factor that affected the crosslinking density was the volume of the chemical crosslinking agent. The results showed that the properly crosslinked PVA fiber aggregates had better antiwater solubility and mechanical properties than the noncrosslinked PVA fiber aggregates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1261–1268, 2002     

银-磷催化剂催化乙二醇制乙二醛及其表面性质

用银－磷催化剂研究了原料气线速、空速、氧醇摩尔比、反应温度、乙二醇重量浓度对催化氧化乙二醇制乙二醛的反应活性的影响．结果表明，在相近的反应条件下，银－磷催化剂能使副产物ＣＯ２的产率从电解银的３０％降到１３．３％，而使乙二醛收率从５４％增至８１％．Ｘ射线光电子能谱表明，在银表面上形成了稳定的表面磷化合物并占据了一部分深度氧化的活性位，因而提高了反应的选择性．     

Glyoxal measurement with a proton transfer reaction time of flight mass spectrometer (PTR‐TOF‐MS): characterization and calibration

We examine the potential for PTR‐TOF‐MS systems to quantitatively measure glyoxal in ambient air by characterizing the response of the instrument to a dilute glyoxal sample, calibrating the system as a function of humidity. The concentration of glyoxal in a sample air‐stream was measured with an UV absorption spectrometer in parallel to a PTR‐TOF‐MS. This calibration demonstrated that the PTR‐TOF‐MS has a relatively low sensitivity to glyoxal particularly at high humidity. Extensive fragmentation of glyoxal to formaldehyde was observed. This behaviour not only desensitizes PTR‐MS system to glyoxal; it may also pose a problem to the quantification of formaldehyde. © 2016 The Authors. Journal of Mass Spectrometry Published by John Wiley & Sons Ltd.     

Pyridine-mediated, one-pot, stereoselective synthesis of acyclic enaminones

A new one-pot, three-component reaction of phenacyl pyridinium bromides, various primary aromatic amines, and phenyl glyoxal or ethyl glyoxalate for the stereoselective synthesis of acylic enaminones in good chemical yields is described.