反应挤出接枝共聚反应表观链增长常数的测量

以预辐照的LLDPE反应挤出接枝MAA作为研究对象,通过在双螺杆挤出机中的不同部位取样,用FTIR分析接枝物及均聚物的产量,并用ESR测试链增长自由基浓度,设计了测定接枝和均聚反应初始阶段的表观链增长常数的方法.结果表明,在本实验测试范围内表观接枝链增长常数不同于均聚链增长常数;所得的测量值符合理论预测值,证明测试方法适合高温熔融体系的研究.     

纤维素与丙烯腈的气相接枝共聚

用高锰酸钾作引发剂活化纤维素,以丙烯腈为接枝单体在气相下反应共聚,考查了引发剂浓度从0.01～0.07N,催化剂浓度从0.01～0.15N范围内的接枝增量,接枝效率和副反应物均聚量的变化,同时也探讨了反应时间、反应温度和含液量的变化对接枝增量,接枝效率和均聚物量的影响。     

自由基接枝共聚的动力学模拟与分析

考察了典型的接枝共聚过程 ,首先由变量相关函数的内涵规律出发 ,在Eu clid空间内拟Tchebycheff意义下的曲线模型 ,对共聚过程中的均聚部分作最佳逼近 ,由此可得到接枝单体浓度的变化规律 .其方法是以数据的回归模拟处理 ,而得到单体变化最切实的描绘 .在此基础上 ,处理了接枝引发过程 .继而在n维线性空间对链增长引为向量分析 ,利用Laplace变换进行递推处理 ,推出包括链转移的接枝链增长的动态过程表达式 ,由此可获得一系列接枝动力学的微观信息 .     

丁二烯－八甲基环四硅氧烷的嵌段共聚合研究 Ⅰ．嵌段共聚物合成及D_4开环动力学

以α－甲基萘钾为引发剂，按顺序加入丁二烯、八甲基环四硅氧烷（Ｄ４）在ＴＨＦ中进行负离子嵌段共聚，制备了聚了二烯－聚二甲基硅氧烷嵌段共聚物．讨论了聚合条件对嵌段共聚合过程的影响．考察了聚了二烯活性链引发Ｄ４进行嵌段共聚的反应动力学，求得在ＴＨＦ中３０℃时Ｄ４开环链增长的表观速率为１０ｋｇ／ｍｏｌ．ｈ、表观活化能为２８．３ｋＪ／ｍｏｌ．     

不同分子量软链段的聚已内酯型聚氨酯扩链反应动力学研究

合成了一系列不同分子量的聚已内酯，进而制备异氰酸根封端的聚已内酯预聚体，用傅里叶变换红外光谱研究了不同分子量的聚已内酯预聚体与二元醇的扩链反应。扩链反应动力学研究结果表明：聚已内酯预聚体与二元醇的扩链反应均为二级反应；随着软链段反应物料分子量的增加，反应速率常数显著降低，但当分子量超过某一范围后，其对反应速率的影响逐渐减小，趋于不变。对于不同硬链段反应物料含量扩链反应体系，硬链段反应物料含量越高，软链段反应物料分子量对反应速率的影响越明显，而且，当软链段反应物料分子量超过某一范围后，不同体系的反应速率常数间的差值趋于不变。Arrhenius方程中的指前因子（B）随软链段反应物料分子量的变化关系与速率常数对分子量的依赖关系相同；从反应速率常数对温度的依赖关系可见：表观活化能的直线斜率基本相同，扩链反应的活化能主要一官能团的反应活性相关。     

窄分布三元醇聚酯的酶催化合成和链增长机理研究

分别以三羟甲基乙烷和辛二酸二乙酯为反应单体，通过酶催化的方式，得到了窄分的树枝状3元醇聚酯。通过¹H-NMR， ¹³C-NMR以及GPC测试表征，我们对比了三羟甲基乙烷聚酯与丙三醇聚酯的链增长行为。结果显示：拥有3个等活性伯羟基的三羟甲基乙烷在与辛二酸聚合过程中，先后经历短时间的接枝链增长和长时间的树枝状链增长，最终形成了结构规则，分子量分布窄的树枝状结构。丙三醇同时含有伯羟基和仲羟基，脂肪酶对伯羟基的选择性催化导致其与辛二酸聚合过程中先后经历线型增长、接枝增长和“接枝+树枝状”增长，最终形成高分子量分布的无规树枝状结构。      

杂多酸引发四氢呋喃聚合反应Ⅴ.生长链浓度与链生长速率常数的测定

采用改进的酚钠法及端羟基测定法对环氧乙烷促进的低浓度磷钨杂多酸引发的四氢呋喃聚合反应过程中生长链浓度的测定表明 ,杂多酸分子中的三个质子均参与了引发反应 ,各引发一个聚合链 .采用醋酸酐为促进剂时杂多酸引发四氢呋喃聚合反应生长链浓度测定的结果也证明了这一点 .由此测得在 0℃和 2 0℃时四氢呋喃聚合反应链增长表观速率常数分别为 3 78× 10 -3 和 1 98× 10 -2 L·mol-1·s-1,这与四氢呋喃按离子型生长链增长时的反应速率常数相近 .说明PW12 引发的THF聚合反应是通过氧离子活性中心增长的     

丁二烯－八甲基环四硅氧烷的嵌段共聚合研究 Ⅰ．嵌段共聚物合成及D4开环动力学

以α－甲基萘钾为引发剂，按顺序加入丁二烯，八甲基环四硅氧烷（Ｄ４）在ＴＨＦ中进行负离了嵌段共聚，制备了聚丁二烯－聚二甲基硅氧烷嵌段共聚物，讨论了聚合条件对嵌段共聚合过程的影响。考察聚丁二烯活性链引发Ｄ４进行嵌段共聚的反应动力学，求得在ＴＨＦ中３０℃时Ｄ４，开环链增长的表观速率为１０ｋｇ／ｍｏｌ．ｈ表观活化能为２８．３ｋＪ／ｍｏｌ。     

烯类单体与可溶性淀粉的接技共聚

甲基丙烯酸与可溶性淀粉在硝酸铈氨(CAN)、高锰酸钾及Fenton’。试剂(Fe~(2+)—H_2O_2)引发下的接枝反应,经历了不同的反应历程。对可溶性淀粉而言,采用Fenotn‘s试剂为引发剂,水—丙酮混合液为介质,可以有效地控制反应,并获得高转化率和高接枝率的最佳效果。通过溶解度参数估算及拟均相反应设计,选择二甲基亚砜(DMSO)为中介溶剂,通过链转移引发完成了油溶性单体苯乙烯与可溶性淀粉间的有效接枝共聚,确定了转化率高、接枝率高、均聚物含量少的最佳反应条件,突破了多年来用相类似化学引发体系引发在苯乙烯与淀粉接枝时转化率低下及均聚物含量高的局限。在上述研究基础上,对反应介质与条件对油溶性烯类单体与可溶性淀粉接枝聚合之接枝参数的影响进行了探讨。     

苯乙烯在顺1,4—聚丁二烯上的接枝共聚反应动力学的Monte Ca …

用Ｍｏｎｔｅ Ｃａｒｌｏ模拟方法对苯乙烯在顺１，４－聚丁二烯上的接枝反应动力学进行了研究。模拟结果表明，对于不同的橡胶浓度，接枝和均聚的聚苯乙烯的数均聚合度、接枝效率与苯乙烯在顺１，４－聚丁二烯上的接枝共聚反应的动力学的解析解十分吻合，证明本方法能够有效地应用于自由基型接枝共聚合反应体系。     

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

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.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.