The classical kinetic experiment in physical chemistry, Belousov-Zhabotinsky (B-Z) oscillating reaction, was redesigned. The mathematical treatment of nonlinear complex reaction kinetics based on the reaction mechanism and the application of B-Z reaction in the detection of silver ions are introduced in the new experimental scheme. The new scheme can deepen students' understanding of nonlinear non-equilibrium kinetics and dissipative structure. Moreover, the numerical method dealing with the complex kinetics can be used in future scientific research and practice.
An asymmetric synthetic experiment that encompasses the knowledge of stereoselectivity and the practice of Schlenk techniques is described. In this experiment, Zn-mediated allylation of an (R)-N-tert-butanesulfinyl imine is performed using different conditions of solvent and additive. The reactions give both diastereomers in good yields and in various diastereomeric ratio (dr), which is determined by 1H, 19F NMR spectroscopy and chiral HPLC. Overall, this experiment can be carried out with readily accessible reagents under mild conditions, and be finished within limited laboratory time. Moreover, it enables students to learn the basics of Schlenk techniques, the differences between enantiomers and diastereomers, how a reversal of stereochemical outcome is realized by tuning the reaction solvent and additive, and the determination of dr regarding optical compounds using HPLC and NMR spectroscopy.
Based on the existing single fountain experiment of ammonia and hydrogen chloride, this experiment designed a continuous operation to integrate the preparation, collection, inspection, exhaust gas treatment, gas reaction, fountain experiment and reagent reuse of the two gases. The experimental principle of the fountain colors includes the coordination reaction of ammonia molecule with copper ion, the precipitation reaction of ammonia water and cobalt chloride solution, the color change reaction of leucophenolic phenolic solution, and acidic reaction of ferric chloride and potassium thiocyanate under acidic conditions. The main apparatus of this experiment was designed and customized by the team, and the operation of the experiment is very simple. The use of glass pistons can control the order of the fountains, thus achieving fountains of various colors. At the same time, with the formation of ammonium chloride, white smoke will be produced, and the colorful fountains are as inlaid in the white clouds, which is spectacular. In addition, we have designed a multi-angle interactive communication program that can transfer multiple levels of knowledge to different audiences, open their minds, and let visitors truly feel the charm of chemistry.
A research-based comprehensive experiment was introduced:co-precipitation synthesis, structure characterization and photoluminescent properties of K2GeF6:Mn phosphors. Chemical redox and co-precipitation method was employed to synthesize K2GeF6:Mn phosphors. By using XRD, SEM and PL spectra characterization techniques, the effects of Mn contents and reactive temperatures on the structure and properties of K2GeF6:Mn phosphors were studied. The red phosphors show great potential in LEDs applications. Through this experiment, students can master the basic laboratory skills; interpret the experimental principles with their basic theoretical knowledge, which will further enhance their scientific research ability and comprehensive application of knowledge.
High content of uric acid can cause gout and other diseases, and thus uric acid is one of the important biochemical indicators in clinical test. Detection of uric acid based on gold nanoparticle colorimetry combines the forefront of scientific research with the content of teaching, which can stimulate students' interest in learning, deepen their understanding of classical theories and increase their understanding of the forefront of scientific research. In this experiment, gold nanoparticles were used to detect uric acid by inhibiting the accumulation of gold nanoparticles induced by melamine after the reaction of uric acid with melamine. With the increase of the concentration of uric acid in the solution, the color of the solution changes from blue to red, and the difference is obvious. The visual effect is good and easy to observe.
This innovative comprehensive experiment mimics the photosynthesis of natural plants and designs a novel photoelectrocatalytic cell of 3D-ZnO/Ni BiVO4/FTO, in which, the ZnO-Ni photocathode prepared by electrodeposition and the BiVO4/FTO electrode were used as photocathode and photoanode, respectively. In 0.1 mol·L-1 KHCO3 aqueous solution, the photoelectrcatalytic CO2 reduction was carried out under -0.6 Volts powered by Si-solar cell in the presence of 1 mmol·L-1 Eosin Y, generating ethanol, acetate acid, and methanol in a total yield of 22.5 μmol·L-1·h-1·cm-2. This process can store solar energy to chemical energy and lessen CO2 in the atmosphere. The students might better understand the principle of green chemistry and the Calvin cycle of plant.
"Physical chemistry experiments" is one of the most important undergraduate chemistry experiment courses in many universities. Comprehensive as they are, these courses suffer from a drawback of lacking an experiment that connects the knowledge between different chapters and to the frontier research of the chemical society. Inspired by a published work of Prof. Dongsheng Guo's group concerning the detection and imaging of cholinesterase using a sequentially activated diacetylene probe, we designed a physical chemistry experiment of "The photopolymerization, thermochromism and application of diacetylene vesicle". We focused on the preparation of diacetylene vesicle, the photopolymerization of diacetylene, the thermochromism of polydiacetylene, and further explored the experiment's potential application on the anti-forgery technology. We hope that by performing this experiment, students can have deeper understanding of different fields of physical chemistry, such as colloid, photochemistry, thermodynamics, dynamics etc., and can know more about current chemistry research on self-assembly, photopolymerization, chromogenic materials, anti-forgery, etc.
In order to bring the concept of green chemistry into basic laboratory teaching and to enhance the exercise on redox reactions, we designed an experiment about the mutual conversion between benzoin and benzaldehyde. In this experiment, benzaldehyde is catalyzed by Vitamin B1 to be converted to benzoin, then benzoin is reduced with sodium borohydride into 1, 2-diphenyl glycol. Afterwards, the product will be oxidated into benzaldehyde under the catalyzing of new green catalyst NaMnOx. 1H NMR was used to authenticate the product in each step of the experiment, and the yield of the oxidation reaction is greater than 90% with HLPC measurement. By completing this cyclic conversion reaction, we conveys the idea of green chemistry to the students, and the students get practice on operating the redox reaction. At the same time, students' cognition and evaluation of chemical reaction can be more complete.
This work is an innovative comprehensive experiment on the preparation of deformable hydrogels and the design as well as the adjustment of their complex shape deformations. A type of poly(N-vinylpyrrolidone)-polyacrylamide (PVP-PAAm) hydrogels with excellent mechanical properties are firstly prepared through free radical polymerization and cross-linking. Poly(sodium acrylate) (PNaAAc) contained in the hydrogels can complex with metal ions like Fe3+, leading to the increase of the cross-linking density of the hydrogels and hence the decrease of their swelling degrees. Through ion-transfer-printing (ITP) and newly developed ion-ink-printing (IIP) techniques, Fe3+ ions are introduced at different positions on one or both sides of hydrogels, changing the local cross-linking density and swelling degree of the surface of hydrogels. Upon swelling or deswelling, the hydrogels can undergo controllable and complex transformations from 1D to 2D, 2D to 3D and 3D to more complicated 3D shapes.
The cyclohexanone preparation is an important experiment in fundamental organic chemistry laboratory for college students. In this paper, NaClO-TEMPO-TBAB catalytic oxidation reaction was used to replace chromic acid oxidation reaction, avoiding concentrated sulfuric acid and chromium-containing waste. At the same time, the reaction conditions were optimized to achieve small scale and shorten operating time which can train and improve students' operation skills in the experiment.
Solid base is considered to be an excellent catalyst for the preparation of renewable energy biodiesel by transesterification. In this paper, a comprehensive experiment is designed on the basis of scientific research results. KF/La2O2CO3 solid base catalyst was prepared by impregnation method, and its phase and surface basicity were measured by X-ray diffraction and temperature programmed desorption with CO2, respectively. In addition, the catalytic activity of KF/La2O2CO3 was tested by using the transesterification of tributyrin and methanol as a model reaction.
Hydrogel, as a kind of polymer material with broad application prospects, is a hot field of scientific research at present. Synthesis of hydrogel is relatively simple, and it combines organic synthesis chemistry, polymer chemistry, inorganic coordination chemistry and analytical chemistry, showing the potential to be adapted to laboratory teaching. Hydrogel is environmentally friendly and fits the theme of green chemistry, which facilitates the introduction of relevant content in the design of laboratory teaching projects. Although green chemistry education plays an increasingly important role in the cultivation of chemical professionals, it has encountered some obstacles in the practical promotion, such as quantitative descriptions, ambiguous concepts and difficulty in stimulating students' interest. Meanwhile, present quantitative calculation of green chemistry only focuses on the mass change before and after reaction. In response to the teaching dilemma of green chemistry as well as translation of advanced scientific achievements, the latest semi-quantitative evaluation method of green chemistry have also been, together with synthesis of hydrogel, introduced to guide students to find the hydrogels synthesis route with high green degree at the stage of experimental preparation. Finally, sodium carboxymethyl cellulose was extracted and modified from waste cotton, and its degree of substitution was determined by titration. Then, metal ion crosslinking method was used to prepare the colored hydrogel product, and its adsorption performance was tested.
A comprehensive chemistry experiment was designed. In this article, the synthesis process of 2-hydroxy-1-naphthalene formaldehyde o-phenylenediamine Schiff base and its copper(Ⅱ) complex was successfully optimized. The composition of the above complex was determined by chemical and instrumental analysis, while the structure was characterized by FTIR and 1H NMR. All of the experimental results are excellent. In general, this experiment could make up for the shortage in teaching synthesis of organometallic coordination compounds. From this experiment, students could consolidate and improve their basic experimental skills such as reflux, purification and centrifugation. They could master the principle and method of the molar ratio method to determine the coordination number and stability constant of complexes. Meanwhile they could understand how to characterize the molecule structure by spectroscopy. It is beneficial for cultivating students' ability to comprehensively apply organic chemistry, inorganic chemistry, chemical analysis and instrumental analysis knowledge to solve specific problems. Besides, it is also helpful for students to understand the properties and research trends of the Schiff base and its metal complexes, stimulating students' enthusiasm for scientific research, cultivating a systematic scientific thinking and research ability.
In the study, we introduced a new organic fluorescence molecule into organic laboratory teaching. A novel course content about fluorescent dimethylaminosylstyrylbenzoxazole was designed. The clear proton response properties of the product can be observed directly. The experiment has many advantages, including new reaction mechanisms, low laboratory risk, simple in operation, observable process changes, and good environmental friendliness. Furthermore, this laboratory course can be divided into a series of unites, which is suitable for different lab teaching time requirements. According to the experiment. We have received good teaching effects. This experiment not only cultivates student's basic operation and comprehensive ability, but also stimulates students' research interest.
The electroreduction of CO2 into value-added chemicals and fuels has garnered a broad interest by using renewable clean energy, due to both alleviating global warming and completing the carbon cycle. Herein, a high-performance Ni-N doped porous carbon catalyst was prepared through pyrolysis of hydrogen containing peptone, NiCl2, and NaCl made by a freeze dry method. The Ni-N-doped porous carbon catalyst displayed an excellent performance of CO2 electroreduction with a Faraday efficiency of 92.0% at -0.66 V (vs. RHE), 550 mV overpotential, and 2.5 mA·cm-2 current density. The catalytic performances were attributed to the Ni-N active sites and porous structures. In addition, CO2 electroreduction to CO was performed continuously by using solar energy, which may provide a valuable reference for carbon cycle in future.
The potential of biocatalysis has been recognized as an efficient and green tool for modern organic synthesis due to its high selectivity, mild reaction conditions and sustainability. The enzyme-catalyzed synthesis of glycerol monolaurate were investigated in this study. The optimized reaction takes place with a 1:3.5 molar ratio of lauric acid to glycerol in the presence of 5% enzyme catalyst at 52℃ for 80 min. The product with 90% purity was obtained in 47%-53% yield via several separation steps. This enzymatic synthesis shows high stability and good repeatability, and is a suitable organic chemistry experiment for undergraduate laboratory teaching.
Using α-amino acids, aldehydes, isocyanides and alcohols as the starting materials, four components react in one pot at room temperature to obtain naturally unique bioactive alkaloids, 1, 1'-iminodicarboxylic acid derivatives. The reaction process is monitored by thin layer chromatography and liquid chromatography-mass spectrometry, and the products are purified by silica gel column chromatography. The structures are determined by mass spectrometry and nuclear magnetic resonance spectroscopy. The reaction is an innovative development of Ugi reaction, which has the characteristics of simple reaction operation, high yield, good stereoselectivity and high atomic economy. It has been widely used in the design and synthesis of new drugs, combinatorial chemistry and natural product synthesis.
This work has been designed as an example in current comprehensive chemistry laboratory course. Firstly, nitrogen was filled into a bomb calorimeter, and sucrose was combusted in this calorimeter using KNO3 as the oxidant and ferric oxide as the catalyst. During combustion of sucrose, change of the temperature was measured through using isothermal calorimeter. Next, the deviation of ΔT was corrected using Reynolds method, and the heat of combustion of sucrose at constant volume was calculated, that is the heat of explosion of nitrosaccharose. When the mass ratio of sucrose-KNO3-ferric oxide was 39:59:2, both the heat of explosion and specific impulse were the largest. Based on the above results, the best proportion of nitrosaccharose fuel was selected for computer simulation of rocket launching system. A series of the specific impulse of nitrosaccharose fuel and the flying height of the rocket were obtained through changing the pressure of combustion chamber and flow rate of nitrosaccharose fuel. In addition, the engine parameters of single-stage rocket for transporting Dongfanghong-1 into the predetermined orbit were calculated through using this simulation system. The engine parameters of multiple-state rockets were also obtained by changing the types and ratio of rocket fuel. As a result, combination of bomb calorimeter experiments and computer simulation system greatly helped innovative design of the current experiment, enlightening creative thought of students.
The preparation of benzyl alcohol and benzoic acid from benzaldehyde by Cannizarro reaction was the common content of organic chemistry laboratory teaching. Nevertheless, due to its time consuming, low yield and inefficient isolating method, this experimental design was far from satisfactory in teaching. The following improvements have been made:Microwave radiation method was introduced, and the synthesis conditions was optimized by orthogonal test design. Under optimized conditions which was 50% KOH, microwave radiation at 500 W for 15 min, the reaction was completed. The yield of benzyl alcohol could reach 82.0%. Benzyl alcohol was isolated by column chromatography instead of distillation, to avoid the formation of distillation by-products. The yield of benzyl alcohol in crude products was determined quickly and accurately by spectrophotometry without separation. The comparison showed that the improved method could reduce the time by 99% and increase the yield by 15%. In addition, the extraction agent was more safe. The improvement was more responsive to the increasing requirements of laboratory training development.
In this experiment, shape memory materials were prepared by using polyvinyl alcohol and tannic acid as the raw material. The inorganic thermochromic materials were prepared by using ethylene diamine tetraacetic acid, copper chloride dihydrate, magnesium chloride hexahydrate and alumina as the raw material. Organic thermochromic materials were prepared by using violet lactone, boric acid and cetyl alcohol as the raw material. The shape memory materials were combined with thermochromic materials to successfully prepare two new composite polymers which can not only remember the shape but also change the color. The experimental materials are simple and easy to obtain, and the method is simple. This experiment uses radical polymerization, chemical cross-linking reaction, complexation reaction, etc., studied in the undergraduate courses of organic chemistry, inorganic chemistry, instrumental analysis, and fine chemical chemistry, and can be used as a comprehensive experiment in undergraduate laboratory teaching to improve students' hands-on ability, stimulate interest and enthusiasm in learning chemistry.
This experiment introduced newly developed photo-induced living/controlled radical polymerization technique, particularly reversible addition-fragmentation chain transfer polymerization (RAFT), which was known as the frontier knowledge in polymer chemistry. Students will find the advantages of photo-induced RAFT polymerization in preparing high-end functionalized polymer through the comparison of photo-induced RAFT polymerization with AIBN initiated RAFT polymerization. The experimental work includes synthesis of regulator, polymerization, separation of polymer, and structure characterization. Students could learn and master skills of design and synthesis of regulator for photo-induced living radical polymerization. They can practice basic laboratory skills, such as organic synthesis and polymerization. Also, they can learn typical characterization techniques of the polymer, which includes gel permeation chromatograph (GPC) and nuclear magnetic resonance (NMR). The aim of this experiment was to enhance the students with creative thinking and to train their fundamental ability for research.
In this experiment, molecularly imprinting polymers (MIP) electrodes with specific recognition ability of bisphenol A (BPA) were prepared by electropolymerization method. O-phenylenediamine was used as the polymeric monomer and BPA as the target molecule. The MIP electrodes were characterized by differential pulse voltammetry and quartz crystal microbalance. Results showed that the electrodes had highly specific recognition ability for BPA. In comparison with the non-imprinting polymers electrode, the recognition ability of MIP was improved by one order of magnitude. 100-fold concentration of atrazine or 17β-estradiol only altered the signal by one-tenth, indicating high selectivity of BPA-MIP electrode in complex matrix. In addition, this experimental design allows flexible target selection. Therefore, after changing the target molecules, the similar MIP electrode could be also successfully prepared by the same method. This experiment allows students to design experiments by themselves. And students can gain an in-depth understanding of the interaction between molecules, and experience the process of designing materials at the molecular level.
Electronic wastes are a rich source of precious metals, e.g., gold (Au), platinum (Pt), palladium (Pd) and silver (Ag). The recycling of these metals has significant environmental importance. This article demonstrated a chemical approach for recycling gold-containing wastes by dissolving gold with safe chemicals. In this reaction, a ligand and gold could form a coordination complex and thus decrease the electrode potential for gold dissolution. The aims of this article are to show the chemistry of chemical reactions using the dissolution of gold as an example, the presence and selection of chemical approaches for tackling some of the increasing environmental problems, the importance of our living environment and problems that we need to tackle with more efforts.
Furfural compounds are unique flavor substances in the food industry, but they have a certain carcinogenic effect when accumulated in human body. Therefore, quantitative analysis of furfural compounds is very important in food industry and environmental detection. In this experiment, coumarin hydroxylamine was used as fluorescent label to derive furfural compounds by nitronization reaction, and the contents of furfural, 5-methyl furfural and 5-hydroxymethyl furfural in milk powder were accurately determined by liquid chromatography-fluorescence detection. The method has the advantages of high selectivity, wide linear range and low detection limit. This innovative experiment is based on the latest research results, and is developed into a research design experiment in "comprehensive chemistry laboratory" course of applied chemistry major. Through all-round experimental operation and training, students can fully understand the relationship between fluorescence and molecular structure, the design and selection of fluorescent derivative reagents, the detection principle and application of modern analytical instruments. By optimizing the test conditions and derivative reaction conditions of the instrument, students can learn how to optimize the experimental design and understand the basic process of scientific research. Thus, it can stimulate students' interest in scientific research, improve their operational ability, cultivate their scientific spirit of diligent thinking, and enhance their innovative ability and comprehensive quality.
Visible light-catalyzed organic reactions have the advantages of high efficiency, operational simplicity, low loading of catalysts under mild conditions, and have received much attention in recent years. The compounds based on the skeleton of imidazo[1, 2-a]pyridine show an impressively wide range of biological activities, such as anti-inflammatory, antiviral activity, antiprotozoal agents, inhibitors of cyclin-dependent kinases, etc. 3-Cyanomethyl-2-phenylimidazo[1, 2-a]pyridine is a key intermediates for the synthesis of the antidepressant drug zolpidem. In our previous work, 3-cyanomethyl-2-phenylimidazo[1, 2-a]pyridine was synthesized via a visible light-promoted reaction of 2-phenyl-imidazo[1, 2-a]pyridine with bromoacetonitrile using fac-Ir(ppy)3 as the photocatalyst. Based on the reaction, herein, the new method about visible light-catalysis was applied to laboratory teaching for broadening the horizons of undergraduates and improving their interests on organic chemistry experiments. Meanwhile, it will help the undergraduates master the basic operations of microchemistry experiments and the use of related instruments. Moreover, this experiment meets the requirements of green chemistry, since it is performed under LED lamp radiation in the absence of toxic reagents. This method also features operational simplicity, low cost, high yield, and good repeatability, etc.
The aggregation-induced emission (AIE) molecules are novel organic fluorescent materials that present distinct photophysical properties in contrast to conventional aggregation-caused quenching fluorescent dyes. In virtue of their unique properties, they can be widely used in many fields such as chemical/biological sensing, biological probing and imaging, diagnosis and treatment integration and optoelectronic devices. In this paper, based on innovative experimental competition, tetraphenylethylene (TPE) side-chain polyacrylate AIE polymers have been synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. With the optimization and exploration of the experimental conditions, the initiator of 2, 2'-azobis-2, 4-dimethylvaleronitrile (ABVN) with shorter half-life and higher activity was adopted to replace the conventional azobisisobutyronitrile (AIBN). As a result, the frontier scientific research experiment, which would have required more than 12 hours reaction, was adapted into a shorter polymerization time of 3-5 hours with moderate yields and good polymer product quality. Thus, the research experiment was remoulded as an experiment suitable for undergraduate laboratory teaching. A range of modern laboratory techniques, such as the anhydrous oxygen-free operation, the column chromatography separation and purification operation, the RAFT controlled polymerization, the gel-permeation chromatography molecular characterization, FTIR, NMR, UV-Vis, and fluorescence emission spectroscopy, have been involved and practised. The photophysical properties of the synthesized TPE side-chain AIE polymers were investigated, with the relative fluorescence quantum yield in the THF/water mixture solution of high water fraction reached a high value of 17%.