茶叶中提取咖啡因实验装置的改进与探索

介绍了使用自动萃取仪和旋转蒸发仪提取咖啡因的实验方法,并用改进的升华装置代替了传统的蒸发皿漏斗法.通过比较现代化学实验手段和常规实验方法的联系和区别,进一步理解现代化学仪器方便、快速、精确的特点.教学过程中,传统方法与现代方法相结合,丰富了有机化学实验内涵和技术手段,提高了学生学习化学知识的兴趣,收到了很好的教学效果.     

咖啡因提取的综合性实验教学

介绍了一个综合性化学实验。该实验以绿茶为原料,95%的乙醇为提取剂,通过索氏提取器提取、常压蒸馏及升华等实验操作,得到咖啡因产品。通过超高效合相色谱法（Ultra Performance Convergence Chromatography,UPC2）确定咖啡因的含量,熔点测定法及1H-NMR归属分析表征结构。本实验将经典的有机化学实验和先进的分析测试仪器相结合,提高了学生的实验综合能力,激发了学生的科研兴趣和探索精神。     

基于培养学生科学实验能力的综合性多步有机合成实验设计与实践:咖啡因的化学合成与表征*

在大学有机化学的经典实验“从茶叶中提取咖啡因”的基础上,设计了以氰乙酸与二甲基脲为原料的“咖啡因的化学合成与表征”综合性实验。该实验操作过程易于控制,重复性较好,通过熔点、紫外、红外、核磁共振、质谱等手段对产物进行了结构表征。通过该实验,学生不仅可以巩固蒸馏、过滤及重结晶等基本实验操作,而且有助于提高对有机化合物合成研究过程的认识,有利于学生综合实验能力的培养。     

咖啡因的升华装置的优化和形象化展现

“茶叶中咖啡因的提取实验”是有机化学的一个经典实验。对传统的升华装置进行了改进,让升华实验更加简单高效,并且能够看到咖啡因晶体聚集和长大的过程,该装置便于咖啡因的收集,能对所收集的咖啡因进行定量计算,同时增加了采用薄层色谱法对浓缩液中咖啡因进行定性鉴定的实验环节。改进的实验丰富了实验内容,降低了实验可能的失误,提高了实验的安全性,创造性地运用实验室的显微熔点仪和智能手机成功地对咖啡因晶体的形貌进行了拍摄,增加了实验的趣味性。     

茶叶中咖啡因的提取实验装置的改进与探索

"茶叶中咖啡因的提取"是有机化学实验的一个经典实验,本文对该实验所用的原索氏提取器进行改进,得到内通气集热式索氏提取器并用于实验教学。通过对照实验,对改进索氏提取器和原索氏提取器的提取效果进行比较。结果表明,改进装置具有原装置的功能和特点,且提取时间更短、提取温度和提取率更高,可在高校推广使用。     

在化学教学中让学生多角度理解化学反应

介绍了中学化学教学中,从物质用途、物质结构、化学实验、物质转化、工业生产等10个不同的角度研究化学反应的一些做法和体会,有利于帮助学生全面地理解化学反应。     

热裂解-气相色谱-质谱法分析烟用咖啡颗粒热裂解特性

利用热裂解-气相色谱-质谱联用分析烟用咖啡颗粒的热裂解特性。分别于150、200、250、300、350℃对烟用咖啡颗粒进行热裂解分析，同时针对不同水分含量和粒径的咖啡颗粒在同一温度下进行热裂解成分分析。结果显示，随着温度的升高，热裂解产物逐渐增多，释放物质的种类逐渐也逐渐增多，在250℃时咖啡颗粒生成关键致香成分占比较高。不同水分含量和粒径的咖啡颗粒在250℃裂解时，水分越高，裂解产物中烟碱含量占比越高，烟气越充足；粒径越小，裂解产物中咖啡因和烟碱的总量越大，香气质量也越高。该试验为咖啡颗粒在卷烟中应用时的温度设计和香气品质改善提供理论依据。     

咖啡因女神的复仇

通过虚构咖啡因女神的复仇计划,以奇幻的手法介绍了咖啡因的历史、化学性质、提取方法、体内代谢途径及生理功能特征。用通俗易懂的语言和扣人心弦的情节科普了咖啡因在体内的作用机制。文中一个少年因无知而顶撞了咖啡因女神,引发女神复仇行动,她引诱少年提取、销售毒品级咖啡因,又因少年的道歉而心软,在交易已经达成之时决定停止复仇。然而少年销售咖啡因却是因其药物性质而非毒品性质,女神的复仇计划落空,皆大欢喜。     

索氏提取器装置的改进与应用

索氏提取器是化学实验常用的提取装置，"茶叶中咖啡因的提取"是有机化学实验中的重要实验。针对传统索氏提取器提取温度低、提取时间长、提取效率低、虹吸管易碎、提取筒和虹吸管易污染或堵塞等弊端，在提取筒外增设外筒，可有效保护虹吸管且对提取筒起加热和保温作用，以提高提取温度和提取效率，缩短提取时间；冷凝管下端改设喇叭口和倒刺，便于悬挂样品袋，防止提取筒和虹吸管受污染或堵塞，由此得到改进装置。并用于茶叶中咖啡因的提取实验以对改进装置进行效果评价。实验数据表明，改进装置不仅克服了传统装置存在的弊端，更保持了传统装置的特点和功能，使用方便安全，提取效率高，值得在高校推广。     

摇头丸中氯胺酮和咖啡因的现场快速检测

采用便携式气相色谱仪,建立了摇头丸中氯胺酮和咖啡因的快速现场检测方法,考察了溶剂种类对提取效率的影响.实验结果表明,以乙醇为提取溶剂,氯胺酮和咖啡因的平均回收率分别为92.3%和95.6%,相对标准偏差分别为5.2%,4.6%(n=5),检测限为0.005 mg/mL,提取液直接经气相色谱检测,检测时间小于3 mini...     

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.     

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.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.