数码成像比色法探究反应物浓度对化学反应速率的影响

利用数码成像比色法探究反应物浓度对化学反应速率的影响,采用紫红色溶液互补光"绿"通道的亮度值-时间的曲线变化表征反应物浓度与化学反应速率的关系。同时也利用分光光度计研究反应物浓度与反应速率的关系,测出透光率-时间的曲线变化。从实验结果比较分析,用数码成像比色法探究反应物浓度对化学反应速率的影响是非常简便可行的方法,同时让学生使用随身所带的电子产品开展实验研究,不仅使实验教学具有趣味性和科学性,而且能更好地培养学生的创新潜质。     

对化学反应速率的实验教学研究

对人教版普通高中教材(必修加选修)中测量化学反应速率的方法进行了改进,将定性实验改进成定量和半定量实验,提出了测量化学反应速率的3种新方法。利用反应物或生成物的性质如生成一定量沉淀所需时间,反应混合物颜色改变所需时间研究了浓度、温度对平均反应速率的影响;对有气体生成的反应,测量反应混合物的质量随时间的减少,或生成气体的体积随时间的增加测量和比较了固体颗粒物大小,催化剂对初始反应速率的影响。     

反胶团萃取铅的动力学机理研究

利用恒界面池研究了二壬基萘磺酸(DNNSA)反胶团溶液萃取模拟电池废水中铅离子的动力学。考察了搅拌转速、DNNSA、初始铅离子浓度以及温度对萃取速率的影响,得到了DNNSA反胶团萃取废水中铅离子的动力学方程并对萃取机理进行了探讨。结果表明,当搅拌速率在200r/min时出现与搅拌强度无关的动力学"坪区",萃取过程为化学反应控制。在动力学"坪区",铅离子萃取速率随着萃取剂DNNSA浓度和水相铅离子浓度增加而增加,温度升高萃取速率加快,萃取反应活化能为35.11k J/mol。     

反应速度实验的改进

通过精心设计的三价铁离子与硫代硫酸根发生的氧化还原反应的实验,揭示了化学反应速度与浓度、温度、催化剂的密切关系。     

铜锌铝催化剂上变换反应动力学的研究 Ⅱ.二维多组分扩散模型及效率因子的数值解

本文研究在铜锌铝催化剂上,一氧化碳变换反应中的气体扩散速率对化学反应速率的影响。建立了各反应气体在柱形催化剂内扩散过程的数学模型;并用正交配置法将模型离散后,以拟牛顿法求得数值解,获得颗粒内的气体浓度分布及催化剂的效率因子,并与其它简化模型作了比较;同时通过实验获得化学反应本征动力学方程及宏观反应速率,从而求得效率因子实验值。二维多组分扩散模型理论计算值与实验值是比较接近的,最高偏差13%,平均偏差为7.5%。而一维模型的偏差比其大2—3%,但能简化计算,节省机时。     

在缓冲溶液中探究高锰酸钾与草酸的反应

以硫酸氢钠-硫酸钠缓冲溶液为反应介质,研究了温度、溶液pH、高锰酸钾浓度以及草酸浓度等因素对高锰酸钾与草酸反应的反应速率的影响。研究发现,升高温度、降低溶液pH（即增大氢离子浓度）以及增大草酸浓度均能加快反应速率,而高锰酸钾浓度对反应速率的影响规律性不强。     

镍基催化剂用于合成气甲烷化的实验研究

实验基于工业用镍基甲烷化催化剂,分别考察了操作温度、原料气CO浓度、操作压力、空速等对合成气(CO浓度5%~25%)甲烷化反应的影响,并分析了造成催化剂失活的因素。结果表明,在300~500 ℃ CH₄的生成速率随着温度的升高、压力的增大、CO浓度的增加而增大。但CO的浓度不能过高,当H₂/CO≤3时催化剂的催化活性会逐步下降。通过XRD、EDS等分析结果得知,催化剂表面存在积炭,催化剂的失活跟积炭有关,通过进一步的对照实验和BET分析表明,积炭的速率与反应温度有关,温度越高积炭速率越快。     

Study on the syngas methanation of nickel-based catalyst

实验基于工业用镍基甲烷化催化剂,分别考察了操作温度、原料气CO浓度、操作压力、空速等对合成气(CO浓度5％～25％)甲烷化反应的影响,并分析了造成催化剂失活的因素.结果表明,在300～500℃CH4的生成速率随着温度的升高、压力的增大、CO浓度的增加而增大.但CO的浓度不能过高,当H2/CO≤3时催化剂的催化活性会逐步下降.通过XRD、EDS等分析结果得知,催化剂表面存在积炭,催化剂的失活跟积炭有关,通过进一步的对照实验和BET分析表明,积炭的速率与反应温度有关,温度越高积炭速率越快.     

负载型Ni-Co-P/CNFs催化剂的制备及释氢性能

以纳米碳纤维(CNFs)为基体材料,采用化学镀法在CNFs表面沉积了Ni-Co-P催化剂。研究了催化剂用量,硼氢化钠、氢氧化钠浓度,温度等对碱性硼氢化钠溶液水解释氢的影响。电感耦合等离子体原子发射光谱法(ICP-AES)测试得出负载型Ni-Co-P催化剂含镍13.30%(质量分数,下同)、钴82.25%、磷4.45%。硼氢化钠水解释氢实验结果表明,产氢速率与催化剂用量呈线性关系。当温度为45 ℃、催化剂浓度为7.5 g/L、氢氧化钠浓度为5%、硼氢化钠浓度为2.5%时,氢气释放速率达到最大值18.044 L/(g·min)。通过对负载型催化剂Ni-Co-P/CNFs催化碱性硼氢化钠溶液释放氢气动力学研究表明,该催化剂的活化能E_a为51.57 kJ/mol。     

催化剂对CaO固硫反应活性的影响研究

用热天平研究了在CaO中添加不同催化剂对固硫反应进程及固硫反应转化率的影响,并采用等效粒子模型处理实验数据,计算了固硫反应两个阶段(表面化学反应控制阶段及产物层扩散控制阶段)的动力学参数。实验表明不同的催化剂对CaO固硫的影响效果和机制不同：催化剂KNO3,NaNO3使表面化学反应活化能和产物层扩散控制阶段反应活化能降低,但同时也使表面化学反应指前因子和扩散系数指前因子降低;而催化剂Fe2O,V2O5增大了表面化学活化能和产物层扩散控制阶段反应活化能,但同时也增大了表面化学反应指前因子和扩散系数指前因子。并发现几种催化剂对活化能和指前因子的影响都具有耦合性,因此单以表面化学反应活化能或产物层扩散控制阶段反应活化能来判断固硫反应活性是不够全面的,应计算出具体温度下的反应速率常数和产物层扩散系数值,才能准确地反映固硫反应的活性。     

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.     

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.     

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.     

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.