木素的氧化性氨化反应(英文)

在一定压力和温度条件下,木素大分子和氨发生反应,生成一些氮修饰木素.为了解反应过程中木素分子结构的变化,用13 C和1H - 13 C 2D -NMRHMQC技术检测了反应前后的分子谱图,结果显示反应过程中木素分子的碎裂化现象十分明显,很可能在氧化性氨化反应过程中,木素大分子表面基团发生了氧化性修饰,如一些侧链 -CH3 被氧化形成 -CHO和 -COOH等,然后这些基团与氨结合等;此外,芳香环结构可能通过粘康酸单体断裂形成一些酰胺类产物,但木素分子内部的高度缩合性结构没有明显的变化     

电化学氧化油页岩反应机理的研究

本文进一步考察了电化学氧化黄县油页岩过程。利用DSC、IR等分析技术研究了反应前后油页岩有机质性质的变化情况。初步认为电解氧化优先发生在油页岩有机质的芳环结构单元上,导致油页岩有机质三维网络结构的破裂,形成大量羧酸。反应过程中的氧化剂主要为阳极产生的活性氧基团而不是分子氧。     

氨基修饰β-环糊精衍生物水相仿生催化不对称Michael加成反应

在不对称 Michael加成反应中,有机小分子如伯胺、吡咯烷类衍生物、(硫)脲类、手性方酰胺、联萘类、奎宁类、手性膦、离子液体和肽类等是目前使用的主要催化剂,如果能避免或少量使用有机溶剂,则更符合“绿色化学”的环境友好发展方向.β-环糊精的内腔疏水,而外部亲水,可以类似酶分子结合有机反应物,在水相体系进行催化反应.当β-环糊精分子上连接催化部位或结合部位时,能产生更优异的包结底物和诱导对映选择性的能力.目前基于β-环糊精衍生物构筑人工类酶催化剂用于不对称 Michael加成反应的报道较少.本文通过亲核取代反应将氨基类有机小分子与单(6-O-p-甲苯磺酰基)-β-环糊精结合,得到9个氨基修饰β-环糊精衍生物CD-1–CD-9(收率在24.2%–64.9%,分子结构通过1H NMR,13C NMR和 ESI-MS表征确认),并用于室温水相体系不对称Michael加成的仿生催化反应,以期获得较好的催化反应活性和对映选择性.通过设计不同β-环糊精衍生物的修饰基团结构、改变反应介质pH值和反应底物结构,分析了Michael加成反应体系产物产率和对映选择性的变化,采用2D-1H ROESY NMR、紫外吸收光谱、红外光谱和和量子化学计算,分析了β-环糊精衍生物和反应底物分子的包结状态,探究了反应过程机理.结果显示,在该水相体系中进行的不对称Michael加成反应产物产率和对映体过量值(ee值)受修饰基团结构、反应介质pH值和底物结构影响较大.当反应介质pH值低于6.0时,由于氨基分子被质子化而失去催化活性;当 pH值为7.5时,获得中等水平的对映选择性,通过量子化学在 ONIOM (B3LYP/6-31G(d)：PM3)水平上的优化计算发现,底物分子与β-环糊精衍生物的包结可以出现两种形式：当底物分子的活性部位接近β-环糊精衍生物小口端的修饰基团时,产生分子内催化,诱导反应产生较好的对映选择性;当底物分子的活性部位远离β-环糊精衍生物小口端的修饰基团时,产生分子间催化,几乎没有对映选择性,而这两种情况同时存在.当底物分子以较大的空间位阻与β-环糊精疏水性空腔结合时,产生较好的对映选择性,邻位取代的2-硝基-β-硝基苯乙烯比对位取代的4-硝基-β-硝基苯乙烯 ee值更高,通过量子化学优化计算证实空间位阻效应.应用2-金刚烷酮与β-环糊精衍生物空腔形成竞争性的包结反应实验,产物产率和ee值都下降,说明β-环糊精衍生物的疏水性空腔是产生不对称诱导和催化活性不可或缺的部分,底物分子与β-环糊精衍生物的包结过程通过2D-1H ROESY NMR和紫外吸收图谱获得确认.其中L-2-氨甲基吡咯烷修饰β-环糊精 CD-1表现出较好的反应对映选择性,在溶剂(pH =7.5,0.5 mol/L CH3COONa-HCl)2 mL,环己酮2 mmol,2-硝基-β-硝基苯乙烯0.2 mmol,CD-1用量0.04 mmol,25°C反应96.0 h的条件下,环己酮与2-硝基-β-硝基苯乙烯 Michael加成产物的 ee值达71%,产率为47%.该反应过程在β-环糊精衍生物的疏水性空腔内进行,修饰基团L-2-氨甲基吡咯烷与环己酮形成烯胺的催化反应.     

酸性体系V催化木质素β-O-4模型物C—C键高选择性切断

研究了酸性体系下NH_4VO_3催化木质素模型物2-(苯氧基)-1-苯乙酮(1a)的C—C键氧化切断过程.通过优选反应溶剂,在温和条件下(100℃,101 kPaO_2)于DMSO-HOAc(V∶V=3∶1)溶剂中高选择性地得到了苯甲酸和苯酚(产率分别为82.1%和88.1%),并通过对反应过程的监测和催化剂的研究提出了该反应可能的反应路径.反应过程存在两条可能的途径,一是1a先发生C—O键断裂生成苯酚和2-羟基苯乙酮,再催化2-羟基苯乙酮C—C键氧化断裂生成苯甲酸;二是1a直接发生C—C键氧化断裂生成苯甲酸和苯酚.同时,催化剂表征结果表明,+5价钒氧离子是催化活性物种.钒催化剂在反应过程中通过+4和+5价循环完成催化过程.     

氨基修饰β-环糊精衍生物水相仿生催化不对称Michael加成反应（英文）

在不对称Michael加成反应中,有机小分子如伯胺、吡咯烷类衍生物、(硫)脲类、手性方酰胺、联萘类、奎宁类、手性膦、离子液体和肽类等是目前使用的主要催化剂,如果能避免或少量使用有机溶剂,则更符合"绿色化学"的环境友好发展方向.β-环糊精的内腔疏水,而外部亲水,可以类似酶分子结合有机反应物,在水相体系进行催化反应.当β-环糊精分子上连接催化部位或结合部位时,能产生更优异的包结底物和诱导对映选择性的能力.目前基于β-环糊精衍生物构筑人工类酶催化剂用于不对称Michael加成反应的报道较少.本文通过亲核取代反应将氨基类有机小分子与单(6-O-p-甲苯磺酰基)-β-环糊精结合,得到9个氨基修饰β-环糊精衍生物CD-1–CD-9(收率在24.2%–64.9%,分子结构通过~1H NMR,~(13)CNMR和ESI-MS表征确认),并用于室温水相体系不对称Michael加成的仿生催化反应,以期获得较好的催化反应活性和对映选择性.通过设计不同β-环糊精衍生物的修饰基团结构、改变反应介质pH值和反应底物结构,分析了Michael加成反应体系产物产率和对映选择性的变化,采用2D-~1HROESY NMR、紫外吸收光谱、红外光谱和和量子化学计算,分析了β-环糊精衍生物和反应底物分子的包结状态,探究了反应过程机理.结果显示,在该水相体系中进行的不对称Michael加成反应产物产率和对映体过量值(ee值)受修饰基团结构、反应介质pH值和底物结构影响较大.当反应介质pH值低于6.0时,由于氨基分子被质子化而失去催化活性;当pH值为7.5时,获得中等水平的对映选择性,通过量子化学在ONIOM(B3LYP/6-31G(d):PM3)水平上的优化计算发现,底物分子与β-环糊精衍生物的包结可以出现两种形式:当底物分子的活性部位接近β-环糊精衍生物小口端的修饰基团时,产生分子内催化,诱导反应产生较好的对映选择性;当底物分子的活性部位远离β-环糊精衍生物小口端的修饰基团时,产生分子间催化,几乎没有对映选择性,而这两种情况同时存在.当底物分子以较大的空间位阻与β-环糊精疏水性空腔结合时,产生较好的对映选择性,邻位取代的2-硝基-β-硝基苯乙烯比对位取代的4-硝基-β-硝基苯乙烯ee值更高,通过量子化学优化计算证实空间位阻效应.应用2-金刚烷酮与β-环糊精衍生物空腔形成竞争性的包结反应实验,产物产率和ee值都下降,说明β-环糊精衍生物的疏水性空腔是产生不对称诱导和催化活性不可或缺的部分,底物分子与β-环糊精衍生物的包结过程通过2D-~1HROESYNMR和紫外吸收图谱获得确认.其中L-2-氨甲基吡咯烷修饰β-环糊精CD-1表现出较好的反应对映选择性,在溶剂(pH=7.5,0.5mol/LCH_3COONa-HCl)2mL,环己酮2mmol,2-硝基-β-硝基苯乙烯0.2mmol,CD-1用量0.04mmol,25°C反应96.0h的条件下,环己酮与2-硝基-β-硝基苯乙烯Michael加成产物的ee值达71%,产率为47%.该反应过程在β-环糊精衍生物的疏水性空腔内进行,修饰基团L-2-氨甲基吡咯烷与环己酮形成烯胺的催化反应.     

具有 MWW 结构钛硅分子筛的研究进展

 综述了具有 MWW 结构钛硅分子筛的制备方法、孔道和晶体结构的调变和修饰以及催化应用三个方面的研究进展. 与 TS-1 相比, 具有 MWW 结构钛硅分子筛的制备方法多种多样; 其孔道结构可塑性强, 通过采用层间剥离、柱撑以及分子水平硅烷化插硅扩孔技术, 可以增大和暴露孔道和外表面, 满足不同选择氧化反应的要求. 由于 MWW 结构钛硅分子筛拥有复杂而独特的孔道结构, 所以在小分子 (如直链烯烃等) 的环氧化反应, 和大分子 (环状烯烃, 二苯并噻吩等) 氧化反应中都表现出优异的催化性能. 此外, 该钛硅分子筛表现出与 TS-1 完全不同的溶剂效应, 用于烯丙基氯液相环氧化与酮类氨氧化反应主产物选择性更高.     

硫酸盐型厌氧氨氧化性能的研究

研究了自养条件下硫酸盐型厌氧氨氧化的性能．试验表明,在无氧条件下,SO4^2-和NH4^＋化学性质稳定,两者间不发生化学反应．在厌氧反应器中接种厌氧消化污泥,经过三年多的连续驯化,可使厌氧反应器发生硫酸盐型厌氧氨氧化（NH4^＋-N和SO4^2-S同时减少）．在高基质浓度下,NH4＋-N和5042-浓度平均降低71．67和56．82mg．L^-1．硫酸盐型厌氧氨氧化的标准吉布斯自由能变化较小,反应可以发生,但不易进行．高基质浓度和低氧化还原电位对该反应有促进作用．     

12顶点[1-R-CB11-Me11]-碳硼烷氧化-还原过程二阶NLO效应的理论研究

采用密度泛函理论（DFT）对12顶点[1-R-CB₁₁-Me₁₁]^-碳硼烷的结构和二阶非线性光学（NLO）调节效应进行计算分析. 结果表明,C位连接的取代基R供、吸电子能力的不同以及分子发生可逆氧化-还原反应对分子构型有一定影响. 由自然键轨道（NBO）电荷和电子自旋密度分析可知,分子的氧化中心是碳硼笼,分子的氧化反应可导致碳硼笼部分给、受体特性发生改变. 氧化态分子的第一超极化率总有效值（β_tot）大于相应还原态分子,当C位取代基R为供电子基团（—NH₂）的分子时,氧化态与还原态的β_tot值变化最大. 这类分子的氧化-还原反应可以有效调节二阶NLO光学效应.     

松柏醇-β-D-葡萄糖苷-[α—^13 C]与造纸废水中LCC的聚合反应

为了有效地去除废水中水溶性、难降解木素及木素碳水化合物复合体(LCC),降低废水的污染负荷.文研究了在木素氧化酶催化下,木素前驱物松柏醇-β-D-葡萄糖苷-[α-13C]与废水中的木素碳水化合物复合体反应的方法及其机理.采用了13C同位素示踪技术,并结合红外谱图分析、核磁共振技术来探讨聚合产物的化学结构.同时应用了GPC分析手段测定了聚合产物的相对分子质量Mn.研究表明:木素前驱物松柏醇-β-D-葡萄糖苷能与废水中LCC发生脱氢聚合反应,同时GPC测定的结果表明聚合后相对分子质量也明显增大,Mn从406上升为23810-36886.反应生成聚合产物为疏水性较好的木素-碳水化合物复合大分子而沉淀析出.     

基于环糊精主客体包合作用构筑的聚合物

在由超分子作用构筑聚合物的研究中,环糊精因能与多种客体分子形成超分子包合物而被广泛应用。本文根据超分子构筑单元的不同,综述了两类基于环糊精主客体包合作用的聚合物:(1)通过具有环糊精及客体基团的大分子间的包合构筑的非共价键嵌段聚合物,包括不同拓扑结构聚合物的制备及其功能化;(2)通过客体基团修饰环糊精的相互包合构筑的超分子聚合物,主要涉及高聚合度超分子聚合物的制备及其研究进展。     

Reactions of lignin in chlorine dioxide bleaching of kraft pulps

The reactions between chlorine dioxide and the residual lignin in oxygen-bleached softwood kraft pulps have been studied. In a first series, isolated lignin samples have been subjected to chlorine dioxide oxidation at different pH values and subsequently analysed by oxidative degradation and elemental analysis. Different analytical techniques have also been employed to follow the gradual chemical changes in lignins isolated from kraft pulps after each of the bleaching stages in the OD(EOP)DD sequence. The results demonstrate that, in order to minimize chlorination of the lignin, the first chlorine dioxide stage should be carried out at a pH around or above three. At this pH level, a high degree of lignin oxidation is also achieved. A certain (mono)-chlorination of the lignin in the first D stage cannot be avoided, but this chlorine is to a large extent removed in the later bleaching stages. The efficient and non-selective oxidation of the various phenolic lignin end groups by chlorine dioxide is clearly illustrated by the analytical data. Moreover,¹³C NMR reveals that reduced lignin structures formed during the kraft cook survive the oxidative bleaching stages to a large extent.     

Ammonolysis of technical lignins

The oxidative ammonolysis of hydrolysis lignin, cellolignin, and lignosulfonate takes place effectively with the greatest formation of a water-soluble fraction at 140–150°C in 2 h. On oxyammonolysis, cellolignin forms approximately twice as much water-soluble fraction as hydrolysis lignin, while lignosulfate desulfonates under conditions exceeding the optimum. The maximum amount of nitrogen in the water-soluble fraction of lignin (nitrogen-containing lignin) amounts to 9.0% for cellolignin and is 2–3% less for the others.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 275–278, March–April, 1987.     

Quantitative1H and13C NMR spectroscopy of lignins from an aqueous ethanolic cook of aspen wood

General and comparative characteristics obtained by¹H and¹³C NMR spectroscopy of the lignins from aqueous ethanolic cooks are presented. It is shown that degradation of the lignin macromolecule takes place during the digestion of aspen wood. The mean length of the lignin side chains decreases and ether bonds are cleaved, while the degree of condensation of the substances increases.Irkutsk State University. Irkutsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 277–285, March–April, 1993.     

Distinction and identification of lignins based on their volatile headspace composition

A new non-degradation methodology is proposed for the distinction and identification of lignins, according to their biological origin and/or isolation methodology, using an electronic aroma sensing system. The system, once trained with representative lignins, could quickly and objectively be used as a simple tool by providing, in real-time, information about the lignin origin, based on their headspace volatile composition. In order to understand which kind of volatile compounds are responsible to the different sensors response present in the headspace, lignins were also analysed by headspace-solid phase microextraction followed by gas chromatography-mass spectrometry detection mode (HS-SPME/GC-MS). Among volatile compounds in the lignin headspace were identified a series of aromatic compounds, C14 to C18 fatty acids and an isoprenoid, squalene. It was proposed that a small proportion of volatile degradation products emerged during the lignin partial degradation during the technogenic process (i.e. delignification) play a key role regarding the aroma sensor response.     

Chemical,Thermal and Antioxidant Properties of Lignins Solubilized during Soda/AQ Pulping of Orange and Olive Tree Pruning Residues

Some agroforestry residues such as orange and olive tree pruning have been extensively evaluated for their valorization due to its high carbohydrates content. However, lignin-enriched residues generated during carbohydrates valorization are normally incinerated to produce energy. In order to find alternative high added-value applications for these lignins, a depth characterization of them is required. In this study, lignins isolated from the black liquors produced during soda/anthraquinone (soda/AQ) pulping of orange and olive tree pruning residues were analyzed by analytical standard methods and Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (solid state ¹³C NMR and 2D NMR) and size exclusion chromatography (SEC). Thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) and antioxidant capacity (Trolox equivalent antioxidant capacity) were also evaluated. Both lignins showed a high OH phenolic content as consequence of a wide breakdown of β-aryl ether linkages. This extensive degradation yielded lignins with low molecular weights and polydispersity values. Moreover, both lignins exhibited an enrichment of syringyl units together with different native as well as soda/AQ lignin derived units. Based on these chemical properties, orange and olive lignins showed relatively high thermal stability and good antioxidant activities. These results make them potential additives to enhance the thermo-oxidation stability of synthetic polymers.     

Cotton plant lignins

This paper generalizes the results of studies on lignins isolated from the stems, bolls, and seed hulls of cotton plants of a number of varieties as functions of the vegetation periods of the plants. The UV, IR and¹H and¹³C NMR spectra of the lignins have been studied. The dioxane lignin (DLA) and the natural lignins have been subjected to nitrobenzene oxidation and to cleavage with sodium in liquid nitrogen. A structure of the lignin macromolecules consisting of 18 phenylpropane structural units has been done up. Information is given on the use of lignins in agriculture, the food industry, and the paint and varnish industry. The anticorrosion and sorption properties of hydrolysis and modified hydrolysis lignins have been studied.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 465–496, July–August, 1997.     

Solution and solid state13C-NMR of barley straw lignins

Grass lignins are formed by the polymerization of phenoxy radicals and contain a variety of carbon-carbon and carbon-oxygen bonds. They are similar to the hardwood lignins, but differ by containing a substantial proportion of esterified cinnamic acids. Detailed nuclear magnetic resonance studies in conjunction with chemical analysis have given new information on the structure of grass lignins. Milled straw lignins (MSL) from barley were examined by both solution and solid-state (CP/MAS) NMR before and after acetylation. The assignment of the carbon-13 (100 MHz) solution spectra was achieved using model compound data, nuclear Overhauser enhancement (NOE) suppression, and insensitive nuclei enhanced by polarization transfer (INEPT) techniques. The NOE suppression permitted quantitative analysis of lignin, giving information on the ratio of specific carbon atoms. Use of the relaxation agent, chromium acetylacetonate, enabled accumulation of sufficient spectral data to give a spectrum suitable for integration after 90 h. The INEPT technique, which had not previously been used for lignin analysis, was successfully applied to acetylated MSL. This technique increased signal intensities 3–4-fold and simplified the spectrum by inverting methylene carbons and eliminating or inverting quaternary carbons. Comparison of this spectrum with the normal spectrum permitted accurate assignment of quaternary and methine carbons. The solid-state carbon-13 CP/MAS NMR was used to examinein situ lignin and the isolated MSL. The¹³C-CP/MAS spectrum ofin situ lignin shows that cellulose and hemicellulose resonances dominate with little evidence ot the aromatic structure of lignin. the¹³C-CP/MAS of MSL shows reduced carbohydrate resonances and increased aromatic resonances. The extent of modification to the barley straw was estimated and results indicate the presence oflignin-carbohydrate complexes. Detailed information on the nature of the linkages between lignin components and between lignin and carbohydrate components has been obtained from these spectra.     

Investigation of Lignins by FTIR Spectroscopy

Summary: Applying special computer mathematical treatments to increase resolution of experimental spectra there were established a set of stable characteristic bands for isolated softwood lignins. In the 740–1620 cm⁻¹ spectral range the band maximum positions did not change but values of bandwidths and peak intensities were varied in limits 15% and 32%. After analysis of the infrared spectra of 30 investigated samples a softwood lignin spectral model was constituted. This model allowed to clear discrepancies in the bands parameters of different mild isolated (lignins of Bjorkman, Pepper and Freudenberg), dioxane and technical lignin spectra. It was helpful for studying lignin structure changes during degradation procedures.     

Thermal Degradation of Hydrolyzed and Oxidized Lignins

The infrared spectra of lignin treated with hydrochloric acid and peroxyacetic acid is investigated. The hydrolysed lignin spectra show a high intensity phenolic OH band at 1375 cm⁻¹ and a decrease in the intensities of CH vibration of methoxyl group at 2920–2810 cm⁻¹ and of the linkage (β–O–4 linkage) at 1120 cm⁻¹. In contrast, the intensity of methoxy group band increases in the case of lignin treated with peroxyacetic acid. This treatment increases also the intensity of the C=O band at 1710 cm⁻¹. The intensity of C=C of aromatic ring band at 1605 and1505 cm⁻¹ is highly affected by the treatment of lignin with peroxyacetic acid, it decreases with large value than in case of lignin treated with HCl. The thermal behavior of these types of lignin has also been studied. The initial and char temperatures of lignin were determined to be 280 and 700°C respectively for unreacted lignin while were 265and 550; 220 and 580°C for lignins treated with hydrochloric and peroxyacetic acid respectively. The rate constants of the mass loss of untreated, hydrolysed and oxidized lignins were found to be 0.05, 0.045 and 0.044 min⁻¹ respectively. This revised version was published online in August 2006 with corrections to the Cover Date.