Volume 7, Issue 3

An Undergraduate Experiment Using Microwave-Assisted Synthesis of First Raw Metalloporphyrins: Characterizations and Spectroscopic Study
Original Research
There is a notable absence in the practical inorganic curricula for experiments in which students can synthesize and characterize series of inorganic complexes. This is possibility attributed to the long required time which is not normally available in regular lab sessions. To address this absence, this paper describes a two-part experiment for chemistry major students in which they prepare series of metalloporphyrins using microwave-assisted technique. In addition to its attractive simplicity, microwave-assisted preparation substantially reduces the needed reaction time to suit the lab session duration. The first lab session is dedicated to the characterization of the 5,10,15,20-tetraphenylporphyrin (TPP) as well as the synthesis of the corresponding Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes. The second session involves the spectroscopic characterization (UV-vis, 1H-NMR, and IR) of the prepared metalloprophyrins. The students relate the experimental results with the provided theoretical data based on quantum chemical calculations.
World Journal of Chemical Education. 2019, 7(3), 225-231. DOI: 10.12691/wjce-7-3-6
Pub. Date: September 20, 2019
13710 Views1424 Downloads
Determination of the p/o-Isomer Product Ratios in Electrophilic Aromatic Nitration of Alkylbenzenes Using High Resolution 1H NMR Spectroscopy
Original Research
High resolution 1H NMR spectroscopy, an increasingly available instrumental method, is used in undergraduate organic laboratory practice as a simpler alternative to gas chromatographic method for the direct determination of the p/oratios of the crude reaction product from the nitration of alkylbenzenes. The choice of isopropylbenzene as a substrate illustrates that steric effect can be significant in controlling regioselectivity in electrophilic aromatic substitution reactions.
World Journal of Chemical Education. 2019, 7(3), 216-224. DOI: 10.12691/wjce-7-3-5
Pub. Date: August 25, 2019
10977 Views1702 Downloads
Astrochemistry as a Gateway to Teaching and Learning Threshold Concepts in Physical Chemistry
The purpose of this paper is to examine the use of astrochemistry examples in teaching the potential threshold concepts (TCs) of physical chemistry that are contained in the recently published Physical Chemistry Anchoring Concepts Content Map (PChem-ACCM). The paper provides a brief overview of how selected astrochemical examples can be utilized to teach and learn suggested TCs that are commonly encountered in the three main overarching areas of physical chemistry curriculum, namely: chemical kinetics, quantum chemistry, and thermodynamics. Using astrochemical examples to decipher the abstract nature of the many fundamental physical chemistry concepts, which are usually accompanied by rigorous mathematical treatments, provides a rich ground in which to implement alternative teaching pedagogies and practices that can help the learner master the associated TCs.
World Journal of Chemical Education. 2019, 7(3), 209-215. DOI: 10.12691/wjce-7-3-4
Pub. Date: July 08, 2019
7843 Views1761 Downloads
Learning Stoichiometry with Spreadsheet Simulations
Original Research
The pedagogical role of simulations in the teaching of chemistry is discussed here, along with the contribution made by simulations designed with spreadsheets, and the possibility of these being created by the students themselves. A sequence of activities is presented for use in the teaching of stoichiometry by means of simple spreadsheets that have the scroll bar incorporated as an interactive resource. Using this method as an alternative to routine ways of doing exercises, students will become more motivated and active, setting up numerical simulations and answering questions like “What happens if…?” Simultaneous visualization of initial and final experimental quantities, and of the stoichiometric relation, makes it possible to deal with students’ alternative conceptions.
World Journal of Chemical Education. 2019, 7(3), 203-208. DOI: 10.12691/wjce-7-3-3
Pub. Date: July 01, 2019
10205 Views2170 Downloads
Copper Dissoliution in Concentrated Sulfuric Acid
Original Research
When redox reactions are studied in the chemistry course, focus is limited to the use of a series of metal activity, electron or electron-ion balance method, and writing of the reaction equations. Students find the redox reactions that occur during the dissolution of metals in acids difficult. Motivated students should be able to solve four problems while studying redox reactions: 1) indicate oxidizing agent and reducing agent; 2) write correct products forming and balance the redox reaction; 3) calculate the electromotive force E0of the redox reaction; 4) indicate the thermodynamic possibility of the occurrence of redox reaction by calculating Gibbs energy ΔG0. The proposed improved methodology for studying the reactions of dissolution of metals in acids allows students to systematize and expand knowledge about redox reactions in inorganic chemistry. To improve the assimilation of knowledge about the dissolution of copper in sulfuric acid, mnemonic scheme has been proposed that makes it possible to understand better composition of the products. Copper reacted with concentrated sulfuric acid only when heated and precipitation of black deposit was observed. The amount of black deposit in the acid and on the surface of copper depended on the method and intensity of heating: heating with interruptions or intensive continuous heating. It has been determined, that during copper dissolution in concentrated 96% sulfuric acid two reactions take place (the main and the parallel) and precipitation of black deposit, consisting mainly of Cu2S and a small amount of Cu2O, is observed.
World Journal of Chemical Education. 2019, 7(3), 196-202. DOI: 10.12691/wjce-7-3-2
Pub. Date: May 29, 2019
16354 Views1931 Downloads1 Likes
Application of Quantitative Proton Nuclear Magnetic Resonance Spectroscopy for the Compositional Analysis of Short Chain Fatty Acid Benzyl Ester Mixtures
Original Research
Nuclear Magnetic Resonance (NMR) has become one of the cornerstones of instrumental analysis work done in chemistry laboratories. NMR is most powerful when used quantitatively, the technique of using NMR to quantify the concentration of an analyte is referred to as qNMR and proton NMR, in particular, is extremely useful in this pursuit to quantify organic compounds. In order to increase exposure to the quantitative and qualitative aspects of NMR in the undergraduate chemistry laboratory, we have created a qNMR experiment to be used in analytical chemistry and instrumental analysis courses. The objective of the experiment was to determine the % composition of a two-component mixture of benzyl acetate (BA), benzyl propionate (BP), and benzyl butyrate (BB). We report on the methodologies used to determine % BA, BP, and BB. Mixtures ranged from 100% to 20%. The results show a strong linear relationship relating known weight %’s with qNMR weight %’s and serves as confirmation of the quantitative utility of proton NMR as well as an educational tool for the undergraduate chemical laboratory.
World Journal of Chemical Education. 2019, 7(3), 189-195. DOI: 10.12691/wjce-7-3-1
Pub. Date: May 20, 2019
19359 Views2026 Downloads20 Likes