木薯淀粉与丙烯酸接枝共聚制备淀粉增稠剂

用过硫酸盐 (过硫酸纳、钾或胺盐 )氧化法使木薯淀粉与丙烯酸接枝共聚。探索到最佳反应温度 55℃ ,反应时间 3h ,单体用量 3.1 2 5mol/L ,引发剂浓度 3.5mmol/L ,接枝百分率可达 70 %以上。产品用作淀粉糊的增稠起到明显的效果     

高分子絮凝剂淀粉接枝丙烯酰胺的合成与应用

通过对硝酸铈铵、过硫酸钾、高锰酸钾三种引发体系的筛选,探讨了引发剂种类及浓度、单体浓度、反应温度、反应时间、玉米淀粉与丙烯酰胺的质量配比等因素对接枝共聚的影响。正交试验表明,当引发剂用量为1.1mmol/L,淀粉用量为35 g/L,AM单体用量为1.48mol/L,反应温度为25℃,反应时间2 h时,粘度最高可达587.83m l/g。用IR、DSC等手段对反应的产物进行了分析表征。选用此接枝物用量50g/t干煤泥,辅以凝聚剂用量1.5kg/t干煤泥进行絮凝试验,有效解决了潘一选煤厂煤泥水中细粒含量多、压滤处理困难的特点,处理能力达75 t/h,滤饼水分可控制在25(左右,滤液水浓度在60g/L左右,与非离子型PAM相比,具有价廉、无毒、絮凝效果好等特点,从环保和应用方面为细粒煤泥水的处理与利用提供了一条有效的途径。     

微波辐照下丙烯酰胺的原子转移自由基共聚合

在微波辐射下,以水为反应介质,2-氯丙酰胺为引发剂,氯化亚铜/2,2′-联吡啶为催化体系,自制的磺基甜菜碱两性离子功能单体3-(2-甲基丙烯酰氧乙基二甲胺基)丙磺酸盐(DMAPS)与丙烯酰胺(AM)单体进行原子转移自由基共聚合反应,得到磺基甜菜碱型两性离子聚合物P(AM-DMAPS)。 讨论了微波功率、反应时间、单体用量、引发剂用量、催化剂和配体用量等因素对聚合反应的影响,并与相应的热聚合法进行了对照。 结果表明,微波辐射功率240 W,反应时间为1250 s时,微波辐射下共聚合的表观速率常数(Kappp)为热聚合法4.5倍,此时AM与DMAPS在水介质中的最佳合成条件为:单体总浓度4 mol/L(其中功能性单体DMAPS在混合单体中所占摩尔分数为1.0%),引发剂浓度0.015 mol/L,催化剂浓度0.01 mol/L。 此时转化率为40.15%,Mn为46410。     

淀粉乙酸酯的阴离子接枝己内酯聚合研究

将淀粉在二甲基甲酰胺、吡啶存在下 ,以乙酸酐进行部分乙酰化 ,制备取代度为 0 7～ 1 9的淀粉乙酸酯 (St Ac) .以萘钠与淀粉乙酸酯中残余的羟基反应 ,将羟基转化为醇盐 (ONa) ,引发己内酯进行阴离子开环接枝聚合 ,合成了淀粉 聚己内酯接枝共聚物 (St g PCL) .采用凝胶渗透色谱法 (GPC)研究了接枝前后聚合物分子量的变化情况 ,并以接枝率、单体转化率对接枝反应进行了表征 .研究了接枝条件如温度、溶剂、引发剂和单体的用量对接枝率及单体转化率的影响 .研究发现随着反应温度升高 ,接枝率、单体转化率呈S曲线变化 ,单体浓度、引发剂浓度的增大有利于接枝反应的进行 .     

丙烯酰胺在离子液体中的原子转移自由基聚合

在1-丁基-3-甲基咪唑四氟硼酸盐离子液体中以氯化苄为引发剂,氯化亚铜/2,2’-联吡啶为催化剂成功实现了丙烯酰胺的原子转移自由基聚合(ATRP)。用IR对聚合物的结构进行了表征,证实聚合物链端具有-Cl端基。考察了引发剂用量、催化剂和配体用量、单体用量和反应时间等因素对丙烯酰胺在离子液体中的原子转移自由基聚合的影响,结果表明,反应时间为1.5 h时转化率达到31.43%,M_n^GPC=4451,M_w/M_n=1.38。且80 ℃下丙烯酰胺在离子液体中的最佳聚合工艺条件为：单体浓度3 mol/L,引发剂浓度0.010 mol/L,催化剂浓度0.015 mol/L,反应时间1 h。     

氯丁胶乳乳液接枝甲基丙烯酸甲酯反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。结果表明,当反应温度为50℃,引发剂叔丁基过氧化氢-四乙烯五胺(t-BHP/TEPA)用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M):m(P)=3:5,乳化剂十二烷基连苯醚二磺酸钠(DSB)用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。聚合反应动力学关系式为:Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40～55℃范围内,聚合反应的表观活化能Ea=60.2kJ/mol。接枝聚合基本符合自由基反应机理。     

Fenton试剂引发淀粉与顺丁烯二酸共聚羧化淀粉

采用Fenton试剂引发淀粉与顺丁烯二酸进行自由基共聚,在淀粉分子链上引入大量羧基,制备淀粉基聚阴离子。探讨了引发剂浓度、反应温度和反应时间对淀粉羧化程度的影响。实验结果表明,淀粉和顺丁烯二酸质量比为1∶1与0.009 85 mol/L亚铁离子、4.412 mol/L H2O2在60℃下反应5 h,得到羧基含量为31.32%的羧化淀粉;控制反应温度、反应时间和引发剂浓度,羧化淀粉的羧基含量可在2.7%~31.5%之间进行调节。FTIR分析验证了羧化淀粉的结构;XRD和TGA的分析结果表明,羧化淀粉的结晶度和分解温度(质量分数20%)均随着羧基百分含量的增大而降低。     

4-烯丁氧基-2-羟基丙磺酸钠接枝改性聚乙烯醇的研究

以水为溶剂,过硫酸铵(APS)为引发剂,将4-烯丁氧基-2-羟基丙磺酸钠(AGES)与聚乙烯醇(PVA)进行自由基接枝反应,对改性反应生成物进行分离得到了AGES-g-PVA接枝物。对AGES-g-PVA接枝物用IR、XRD、DTA和TG进行了结构表征。结果表明:随着引发剂浓度增大、AGES用量提高、反应时间延长及反应温度的升高,AGES对PVA接枝率增大。     

高锰酸钾/硫脲引发魔芋粉-丙烯酰胺接技共聚合及产物增稠性研究

用高锰酸钾／硫脲为引发剂，引发魔芋粉(KGM)与丙烯酰胺(AM)的接枝共聚。研究了引发剂浓度、单体浓度、酸度、反应温度、反应时间、反应介质以及KGM预处理方式等对接枝反应的影响，同时还研究了产物的水溶性及增稠性，并探讨了接枝反应机理。     

氯丁胶乳乳液接枝甲基丙烯酸甲酯的反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。 研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。 结果表明,当反应温度为50 ℃,引发剂叔丁基过氧化氢 四乙烯五胺（t-BHP/TEPA）用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M)∶m(P)=3∶5,乳化剂十二烷基连苯醚二磺酸钠（DSB）用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。 聚合反应动力学关系式为：Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40~55 ℃范围内,聚合反应的表观活化能Ea＝60.2 kJ/mol。 接枝聚合基本符合自由基反应机理。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).