奥克托金(HMX)的T-Jump/FTIR快速热裂解研究

采用T-Jump/FTIR快速热裂解原位红外光谱联用技术研究了奥克托金(HMX)在0.1,0.2,0.3和0.4MPa的Ar气条件下,以1000℃·s-1的升温速率快速升温至设定的反应温度,用快速扫描傅立叶变换红外光谱跟踪分析分解产物的种类和相对摩尔浓度的变化,研究了温度及压力对初始检测产物的影响.结果表明,HMX在快速热裂解5s过程中红外所检测到的主要气相产物为CO,CO2,NO,NO2,N2O,HCONH2,CH2O,H2O,HNCO及HCN,并给出了这些产物相对摩尔浓度随时间变化的曲线.根据气体产物相对摩尔浓度的比率N2O/HCN,研究了压力和反应温度对HMX的快速热裂解过程及机理的影响,认为在低温HMX分解的C—N键断裂在两竞争反应中占优,通过压力的变化证明了气相产物之间存在二次反应.     

新型侧基含磷共聚酯的阻燃和热降解动力学

利用动态热重分析法(TG)研究了聚酯(PET )及侧基含磷共聚酯(FR-PET)在不同升温速率下的热稳定性及热降解动力学, 并通过极限氧指数法(LOI)考察了FR-PET的阻燃性能; 采用Flynn-Wall-Ozawa方法分析了PET和FR-PET的热降解表观活化能; 利用Coast-Redfern方法通过对不同机理模型的选取, 确定了PET和FR-PET热降解动力学机理及其模型, 得出了主降解阶段的非等温动力学方程及热降解速率曲线图. 研究结果表明, 侧基含磷单元的引入提高了聚酯的阻燃性能, 侧基上的P—C和P—O键易断裂, 从而降低了聚酯的热稳定性. PET和FR-PET的热降解表观活化能(0.1≤α≤0.85)分别为194-227和184-209 kJ/mol; PET和FR-PET热降解反应均属于受减速形α-t曲线控制的反应级数机理, 其机理函数为f(α)=3(1-α)2/3(0.1≤α≤0.85). 侧基含磷单元的引入对PET的主降解阶段的热降解速率并无实质上的影响. 侧基含磷共聚酯的凝聚相阻燃作用有限, 可能以气相阻燃机理为主发挥阻燃作用.     

DSC分析及原位FT-IR法对聚合物接枝碳纳米管/环氧树脂固化体系的固化反应的研究

合成了一种扩链脲修饰的多壁碳纳米管(MWCNT-PEG-TU),差示扫描量热分析(DSC)结果表明,MWCNT-PEG-TU可明显提高E-51环氧树脂/双氰双胺(DICY)固化体系的固化反应活性。利用原位傅里叶变换红外光谱(in situ FT-IR)法研究了MWCNT-PEG-TU/E-51环氧树脂/DICY固化体系的等温固化动力学,该固化体系在不同温度下的dα/dt与α的关系曲线较好地符合Kamal自催化反应模型。     

BMI/DDE/F-51 环氧树脂的固化及其热稳定性

以双马来酰亚胺(BMI)/二氨基二苯醚(DDE)组合固化剂对酚醛环氧树脂(F-51)进行固化,得到了BMI/DDE/F-51 固化体系,将该体系与单一固化剂固化的 BMI/F-51、DDE/F-51 体系进行比较,探求其固化机理和热稳定性.用差示扫描量热仪(DSC)研究了BMI/DDE/F-51 的固化反应动力学,求得固化反应表观活化能 Ea=60.86 kJ/mol、碰撞因子 A=2.04×106s-1和反应级数 n=0.89;用傅里叶变换红外光谱(FT-IR)对反应历程进行了探讨;用热失重分析仪(TGA)研究BMI/DDE/F-51 固化树脂的热分解动力学,确定了热稳定性能良好的耐高温环氧树脂新体系,其热分解反应表观活化能为 BMI/F-51 或 DDE/F-51 固化体系的3倍以上,达 166.08 kJ/mol.     

TGA和Py-GC/MS研究不同氛围下烟草的热失重和热裂解行为

应用热重红外联用技术(TG-FTIR)和热裂解气相色谱-质谱联用技术(Py-GC/MS)对卷烟烟丝的热失重和热裂解行为及其裂解产物进行研究.采用热重分析法测定不同气氛下卷烟样品的热失重(TG)、微商热重(DTG)曲线,以及热裂解过程中H2O、CO2、CO、NH3和CH4等气体物质的释放量.结果表明,裂解气氛不同可以显著...     

热致性液晶聚合物的种类对液晶/环氧树脂共混物固化反应动力学的影响

采用等温DSC固化动力学研究方法,用自催化动力学模型对反应型热致性液晶聚合物/环氧树脂共混体系进行研究.结果表明,EP/DDS未改性体系,在α＜40%范围遵循自催化反应机理;EP/DDS/LCPU共混改性体系,在α＜60%范围遵循自催化动力学反应机理,而且自催化反应速率和非催化反应速率均大于未改性体系,表明反应型热致性液晶聚合物的活性基团对固化反应起到了催化促进作用;EP/DDS/PHBHT共混改性体系能够较好符合n级反应机理,固化反应的活化能较大,说明没有反应基团的液晶聚合物(PHBHT)对固化反应无明显促进作用.     

基于TGA-FTIR联用技术研究ABS树脂的热氧降解行为

采用热失重-傅立叶变换红外光谱(TGA-FTIR)联用技术研究了空气气氛下ABS树脂的热稳定性及热氧降解失重情况。研究了ABS在4个不同升温速率下的失重情况;采用TGA-FTIR联用技术对10℃/min等速升温下ABS失重过程的逸出气体进行分析;采用热分解动力学方法分析ABS的热氧降解过程,计算热分解活化能。结果表明,ABS的TGA曲线有两个失重区间:第一区间是ABS的急剧氧化降解过程,活化能(Ea)为191.8~262.8 kJ.mol-1,第二区间是成炭产物的氧化,Ea约为139.7 kJ.mol-1;升温速率越小,ABS热氧降解速率越慢,交联成炭产物越多,有利于抑制ABS的降解;由FTIR测试和Ea变化发现,热氧降解反应为多步复杂反应,初期时氧化反应和氧化断链同时进行,并以氧化断链反应为主,随着分子链上产生的双键增多发生交联反应,失重率大于80%时开始炭化反应,最终交联炭层发生氧化反应生成CO2。     

α- Fe2O3-TiO2复合晶膜的制备及光催化特性的研究

α-Fe2O3和Ti02均为n型半导体，在紫外光照射下可使亚甲基蓝发生氧化还原反应，使之降解．α-Fe2O3禁带宽度(2．2eV)比Ti02的禁带宽度(3．1eV)小，而其吸收光于的效率大于Ti02，在催化降解亚甲基蓝时表现出比Ti02更高的活性．α-Fe2O3-Ti02复合晶体的光吸收强度要比单一α-Fe2O3晶体的光吸收强度明显增强．在α-Fe2O3中掺入少量Ti02后，在紫外光照射下对亚甲基蓝的降解显示出更高的活性．     

含芳基噻唑基团环氧树脂材料的制备及热性能

制备了一种含芳基噻唑基团热稳定环氧树脂材料(TDABZ),通过傅里叶变换红外光谱(FTIR)对其结构进行了表征,采用热重分析-微熵热重分析(TGA-DTG)计算了TDABZ的热分解动力学参数,利用热重分析(TGA)和动态热机械分析(DMTA)探讨了TDABZ的耐热性能。 结果表明,TDABZ通过TGDDM结构中的环氧基团与混合固化剂(DDS和2-ABZ)结构中的活泼氢反应,在较低的温度下就能完全交联固化。 通过Kissinger和Ozawa方法求得TDABZ的热分解活化能分别为205.5和221.9 kJ/mol。 TDABZ固化物具有优异的耐热性能,双悬臂梁法测得的玻璃化转变温度(T_g)达到242.3 ℃,在N₂气气氛下失重5%对应的温度(T_d5)为340.2 ℃,最大失重速率对应的温度(T_dmax)为395.5 ℃,600 ℃的质量保留率为24.1%,显著提高了环氧树脂的热稳定性能,拓宽了其应用领域。     

光敏性季铵盐的合成与性能研究

制备了α-二乙氨基苯乙酮并在醋酸环境下将该化合物与苯基缩水甘油醚（PGE）反应合成了以醋酸根为配对阴离子的、具有芳酮结构的光敏性季铵盐（α-PGE－A），通过红外吸收光谱，核磁共振谱及热重分析对α-PGE－A紫外光辐照前后的结构进行了研究。红外光谱显示α-PGE－A经紫外辐照后，其羰基吸收峰显著增强，醋酸根离子吸收峰消失；核磁共振研究表明样品光照后可能生成频胺及醋酸酯。α-PGE-A与环境树脂复配合的热固化研究显示，经紫外光辐照后的样品热固化较易进行完全。表明α-PGE-A具有一定光产碱活性。     

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%.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.