杂多酸引发甲氢呋喃开环聚合反应——Ⅶ.以1，1，1—三羟甲基丙烷为分子量调节剂

聚氨酯是由硬段和软段组成,其中的软段主要来源于聚醚或聚酯,通过化学交联反应可改变聚氨酯的力学性能,由过氧化物引发或使用小分子的三醇作为扩链剂对聚氨酯的硬段进行化学交联,所得聚氨酯的性能会变坏;而使用环氧丙烷（PO）与四氢呋喃（THF）的共聚醚三醇来制备在软段化学交联的聚氨酯,所得聚氨酯与由PO－THF共聚醚二醇制备的聚氨酯相比,断裂伸长率有轻微的下降,但抗拉强度得取了很大改善,由此可见,通过聚醚多元醇对聚氮酯的软段进行化学交联,有利于改善其力学性能。     

用三氟化硼引发体系制备聚丁二醇

分子量在3000以下特别是1000或2000的聚丁二醇(PTMG)是制备嵌段聚醚聚氨酯及嵌段聚醚聚醋弹性体的重要软段原料。用三氟化硼(BF_3)体系引发制备PTMG巳有报道,但尚难在工业上采用,主要是引发效率低。前已报道,BF_3-环氧氯丙烷(ECH)体系的引发效率比BF_3-环氧乙烷(EO)体系高2.5～6倍,比BF_3-环氧丙烷(PO)体系高2～3倍。本文用BF_3-ECH为引发体系,并用水为分子量调节剂制备分子量1000或2000的PTMG,测     

三氟化硼引发四氢呋喃聚合的研究——以环氧氯丙烷为促进剂

<正> 四氢呋喃(THF)通过正离子开环聚合而制得的聚丁二醇(PTMG)是生产嵌段聚醚聚氨酯及嵌段聚醚聚酯弹性材料的重要原料。目前制备PTMG所采用的引发剂都是强酸型的,如高氯酸、氟磺酸或发烟硫酸等,对设备腐蚀严重。用酸性较弱的三氟化硼引发聚合在文献上也有一些研究报道,但尚难以采用,其主要困难在于实际应用的     

三氟化硼引发四氢呋喃聚合的研究——Ⅱ. 水的影响

<正> 分子量在3000以下的四氢呋喃聚合产物-聚丁二醇(PTMG)是重要的工业原料。前报中我们已证明用BF_3-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合时引发效率较高,在这一基础上有希望通过在聚合体系中加水以达到控制产物分子量的目的。 文献上对水在BF_3-ECH引发THF聚合反应中作用的研究不多,Kyzaeb等人     

三氟化硼引发四氢呋喃聚合的研究——Ⅳ.1,4-丁二醇的影响

前报中已证明用三氟化硼-环氧氯丙烷(ECH)引发四氢呋喃(THF)聚合具有较高的引发效率,并对在Ac_2O、水和无水存在下的聚合反应进行了研究。本文报道1,4-丁二醇(BG)对BF_3引发THF聚合反应的影响。通常认为在BG存在下,BF_3是不能引发THF聚合的,但本工作证明BG是有效的分子量调节剂,制备分子量在     

四氢呋喃-环氧丙烷双端正离子活性共聚醚链的研究

迄今为止,对四氢呋喃(THF)活性共聚合的研究报导甚少。THF均聚醚在分子量大于2000时易结晶使嵌段共聚产物性能变坏,因之THF活性共聚合的研究对嵌段共聚具有重要意义。     

聚氧乙烯功能基复合修饰聚氨酯的合成及其血液相容性研究 (Ⅰ)──聚氨酯-接枝-十八烷基聚氧乙烯

通过十八烷基聚氧乙烯和环氧氯丙烷的封端反应制备了α-环氧基-ω-十八烷基聚氧乙烯大单体.并采用BF₃·Et₂O引发THF和大单体共聚合,得到了梳状的十八烷基聚氧乙烯接枝共聚醚.以该共聚醚为软段合成了十八烷基和聚氧乙烯复合修饰的聚氨酯(PEU-g-PEO-C₁₈).通过血小板粘附试验对材料的体外抗凝血性实验结果表明,采用具有选择性吸附白蛋白功能的十八烷基和PEO复合修饰聚氨酯,材料表面血小板粘附量明显减少.材料血液相容性的改善可能来源于疏水性的十八烷基和亲水性聚氧乙烯的协同作用.     

添加剂对EO/THF共聚醚聚氨酯热氧降解的影响

添加剂对EO/THF共聚醚聚氨酯热氧降解的影响     

链段相容性对聚酯-聚醚多嵌段共聚物组成均一性的影响

<正> 由结晶型芳族聚酯为硬链段,无定型脂肪族聚醚为软链段的聚酯-聚醚多嵌段共聚物,是一类性能优良的热塑弹性体,本文研究链段相容性对这类聚合物组成均一性的影响,因此,合成了一系列不同链段结构的聚酯-聚醚多嵌段共聚物。 如硬链为聚对苯二甲酸乙二醇酯(PET)和丁二醇酯(PBT);软链段有聚乙二醇醚(PET)、聚丁二醇醚(PTMG)、聚二醇醚(PPG)和四氢呋喃同环氧丙烷的共聚醚二醇     

四氢呋喃/环氧乙烷共聚醚与N-100固化反应机理(Ⅰ)──NMR研究催化活性与反应物的相互作用

采用高分辨核磁共振方法研究聚醚聚氨酯脲反应体系中四氢呋喃/环氧乙烷共聚醚和固化剂N－100及催化剂之间的相互作用.结果表明共聚醚的羟基和N－100的异氰酸酯基因之间存在相互作用,能够形成一种相对稳定的络合物.催化剂二月桂酸二丁基锡(DBTDL)能与共聚醚的羟基氧络合,从而使羟基氢活化;催化剂三苯基铋(TPB)及其乙氧基取代的衍生物与共聚醚羟基氢之间存在弱氢键作用.其强度随TPB乙氧基衍生物的碱性增强而增大.当DBTDL和TPB同时存在于反应体系中时,羟基上的氧和氢均被活化,表现为协同作用.     

四氢呋喃开环聚合的研究——Ⅳ.发烟硫酸-高氯酸引发四氢呋喃及环氧丙烷的共聚合

用21％或28％发烟硫酸-高氯酸引发四氢呋喃及环氧丙烷(THF:PO=100:5-15(克))进行共聚合反应,收率为50—60％,四氢呋喃的损耗不超过10—15％,产物分子量在1000—2000之间可调。与通常用三氟化硼或五氯化磷及二元醇制备的四氢呋喃-环氧丙烷共聚醚不同;当环氧丙烷用量低时,收率并不降低;产物的端羟基官能度为2;以伯醇端基为主(约65—70％)。     

苯磺酸修饰的层柱磷酸锆的制备及催化应用

以共缩合方法制备了一系列苯磺酸修饰的层柱磷酸锆材料,利用N2吸附、Si核磁共振、红外光谱和热重分析等方法对其结构进行了表征. 将其应用于对苯二酚与叔丁醇烷基化反应中,结果发现催化剂合成时的投料比对其催化性能有较大的影响,催化剂ZrP-0.4-2-10%-PhSO3H的催化性能最佳,反应4 h对苯二酚的转化率为85.4%,2-叔丁基对苯二酚得率达到58.5%. 酸性表征结果显示,催化剂活性与其表面可接触酸性位的数目密切有关. 该催化剂还具有较好的重复利用性能,反应3次后产物得率仅下降10%. 催化剂失活是由于磺酸基团的脱落或活性位被积碳覆盖所引起.     

STUDIES ON THE RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN Ⅳ. COPOLYMERIZATION OF TETRAHYDROFURAN AND PROPYLENE OXIDE INITIATED BY FUMING SULFURIC ACID AND PERCHLORIC ACID CATALYST SYSTEM

The yield of copolymerization of tetrahydrofuran and propylene oxide (THF:PO=100:5—15, by wt.) using a binary catalyst of fuming sulfuric acid (21% or 28%) and perchloric acid is around 50—60%, and the loss of THF in the reaction is below 10—15%. The average molecular weight of the product can be controlled in the range of 1000—2000 by varying the binary catalyst system. The present method, which is different from the usual copolymerization initiated by BF_3-diol or SbCl_5-diol system, shows the pecularities i.e. the yield of copolymerization with the low PO feed is not decreased, the hydroxyl functionality is equal to 2, and the end-groups are predominantly primary hydroxyls (around 65—70%).     

Synthesis of Pb(OH)2/rGO Catalyst for Conversion of Sugar to Lactic Acid in Water

Conversion of sugars from biomass to platform chemicals or fuels is an attracting topic for the utilization of biomass. Pb²⁺ ion is an efficient catalyst for the degradation of sugar to lactic acid, and it will be better to fix lead on a solid catalyst to reduce the risk of exposure of Pb²⁺ to environment. Here, a simple method has been developed to prepare a composite catalyst of Pb(OH)₂/rGO, where the nanoparticles of Pb(OH)₂ in size of 2-5 nm were prepared and fixed over the as-prepared reduced graphene oxide (rGO) nanosheets. The as-obtained catalyst showed an efficient catalytic activity to degrade glucose, fructose, and cellulose in aqueous solution, and the major product is lactic acid. The yield of lactic acid reached 58.7% when fructose was used as the feedstock (433 K and 2.5 MPa N₂), and the catalyst can be recycled with high activity. Cellulose can also be directly converted into lactic acid in aqueous solution over the catalyst without extra acid or alkali, and the maximum yield of lactic acid is 31.7%.     

二氧化硒催化过氧化氢氧化萘丙醛制萘丙酸的研究

萘丙酸((±)-2-(6-甲氧基-2-萘基)-丙酸)的右旋体有解热镇痛特效,国内生产中由萘丙醛氧化成酸系采用多伦试剂,耗费大量硝酸银。我们采用过氧化氢作氧化剂,结果表明,制得的产品纯度高,而且成本低。     

Partial oxidation of 4-tert-butyltoluene catalyzed by homogeneous cobalt and cerium acetate catalysts in the Br-/H2O2/acetic acid system: insights into selectivity and mechanism

The partial oxidation of 4-tert-butyltoluene to 4-tert-butylbenzaldehyde by hydrogen peroxide in glacial acetic acid, catalyzed by bromide ions in combination with cobalt(II) acetate or cerium(III) acetate, has been studied in detail. Based on the observed differences in reaction rates and product distributions for the different catalysts, a reaction mechanism involving two independent pathways is proposed. After the initial formation of a benzylic radical species, either oxidation of this intermediate by the metal catalyst or reaction with bromine generated in situ occurs, depending on which catalyst is used. The first pathway leads to the exclusive formation of 4-tert-butylbenzaldehyde, whereas reaction of the radical intermediate with bromine leads to formation of the observed side products 4-tert-butylbenzyl bromide and its hydrolysis and solvolysis products 4-tert-butylbenzyl alcohol and 4-tert-butylbenzyl acetate, respectively. The cobalt(II) catalysts Co(OAc)(2) and Co(acac)(2) are able to quickly oxidize the radical intermediate, thereby largely preventing the bromination reaction (i.e., side-product formation) from occurring, and yield the aldehyde product with 75-80 % selectivity. In contrast, the cerium catalyst studied here exhibits an aldehyde selectivity of around 50 % due to the competing bromination reaction. Addition of extra hydrogen peroxide leads to an increased product yield of 72 % (cerium(III) acetate) or 58 % (cobalt(II) acetate). Product inhibition and the presence of increasing amounts of water in the reaction mixture do not play a role in the observed low incremental yields.     

Contribution to the chemistry of the Belousov-Zhabotinsky reaction. Products of the Ferriin-Bromomalonic acid and the Ferriin-Malonic acid reactions

In the present mechanistic schemes of the ferroin-catalyzed oscillatory Belousov-Zhabotinsky (BZ) reaction the oxidation of the organic substrates (bromomalonic or malonic acid) by ferriin (the oxidized form of the catalyst) plays an important role. As the organic products of these reactions were not yet identified experimentally, they were studied here by an HPLC technique. It was found that the main organic oxidation product of bromomalonic acid is bromo-ethene-tricarboxylic acid (BrEETRA), the same compound that is formed when bromomalonic acid is oxidized by Ce4+ (another catalyst of the BZ reaction). Formation of BrEETRA is explained here by a new mechanism that is more realistic than the one suggested earlier. To find any oxidation product of malonic acid in the ferriin-malonic acid reaction was not successful, however. Neither ethane-tetracarboxylic acid (ETA) nor malonyl malonate (MAMA), the usual products of the Ce4+- malonic acid reaction, nor any other organic acid, not even CO2, was found as a product of the reaction. We propose that malonic acid is not oxidized in the ferriin-malonic acid reaction, and it plays only the role of a complex forming catalyst in a process where Fe3+ oxidizes mostly its phenantroline ligand.     

9-fluorenylphosphines for the Pd-catalyzed sonogashira, suzuki, and Buchwald-Hartwig coupling reactions in organic solvents and water

The lithiation/alkylation of fluorene leads to various 9-alkyl-fluorenes (alkyl=Me, Et, iPr, -Pr, -C18H25) in>95% yields, for which lithiation and reaction with R2PCl (R=Cy, iPr, tBu) generates 9-alkyl, 9-PR2-fluorenes which constitute electron-rich and bulky phosphine ligands. The in-situ-formed palladium-phosphine complexes ([Na2PdCl4], phosphonium salt, base, substrates) were tested in the Sonogashira, Suzuki, and Buchwald-Hartwig reactions of aryl chlorides and aryl bromides in organic solvents. The Sonogashira coupling of aryl chlorides at 100-120 degrees C leads to>90% yields with 1 mol% of Pd catalyst. The Suzuki coupling of aryl chlorides typically requires 0.05 mol% of Pd catalyst at 100 degrees C in dioxane for quantitative product formation. To carry out "green" cross-coupling reactions in water, 9-ethylfluorenyldicyclohexylphosphine was reacted in sulphuric acid to generate the respective 2-sulfonated phosphonium salt. The Suzuki coupling of activated aryl chlorides by using this water-soluble catalyst requires only 0.01 mol% of Pd catalyst, while a wide range of aryl chlorides can be quantitatively converted into the respective coupling products by using 0.1-0.5 mol% of catalyst in pure water at 100 degrees C. Difficult substrate combinations, such as naphthylboronic acid or 3-pyridylboronic acid and aryl chlorides are coupled at 100 degrees C by using 0.1-0.5 mol% of catalyst in pure water to obtain the respective N-heterocycles in quantitative yields. The copper-free aqueous Sonogashira coupling of aryl bromides generates the respective tolane derivatives in>95% yield.     

Synthesis of optically active methyl 4-(4-biphenylyl)-3-hydroxybutanoate via enantioselective hydrogenation using a tartaric acid-modified nickel catalyst and recrystallization

Enantioselective hydrogenation of methyl 4-(4-biphenylyl)-3-oxobutanoate over a tartaric acid-modified Raney nickel catalyst gave the title compound in 82% ee, which was enantiomerically enriched by recrystallizations. The product was converted to an (R)-3-acetoxyglutaric acid half ester via a ruthenium-catalyzed oxidation.     

固体酸SO_4~(2-)/ZrO_2-MoO_3催化合成富马酸二甲酯

在固体酸SO2-4/ZrO2 MoO3催化下,由马来酸酐和甲醇催化合成了富马酸二甲酯.探讨了催化剂用量,原料配比,反应时间对产率的影响.最佳反应条件为:醇酸摩尔比为6∶1,反应时间3h,催化剂占反应物总质量的1.5%,产物收率在93%以上.