Volume 9, Issue 3

Why the Second Bond Exceptionally Effective on pKa Values of -ynoic (-C≡C-) Compounds? Chemical Education Perspective
Sudden decrease of nearly more than two orders of magnitude of pKa units of ynoic series of compounds is explained based on the electronegativity differences of sp, sp2 and sp3 carbons and on the subsequent stability of the corresponding anions. Both resonance and inductive effects operate in tandem to stabilize the ynoic anions.
World Journal of Chemical Education. 2021, 9(3), 94-95. DOI: 10.12691/wjce-9-3-5
Pub. Date: November 15, 2021
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Introduction of a Computational Chemistry Course-Based Undergraduate Research Experience (CURE) into an Advanced Organic Chemistry Lab: An Investigation of Propellane Formation
Original Research
The introduction of basic computational chemistry concepts is becoming an integral part of any complete undergraduate curriculum in chemistry. The advanced organic chemistry course affords laboratory time in which some focused study of computational chemistry is possible. Although learning how to carry out basic computational manipulations is important, interest in computational chemistry can be instilled by carrying out a research-like experience. We incorporated a course-based undergraduate research experience (CURE) into our advanced organic chemistry lab course in which students, as a group, studied the spontaneous formation of strained propellane compounds from the corresponding anionic bridgehead bromide precursor compounds. Completing the calculations and data analysis as a class simulated a true research project, and led to the discovery of results from which interesting conclusions were drawn. Student feedback was generally very positive and suggested that this project gave them a strong sense for how computational chemistry research is conducted.
World Journal of Chemical Education. 2021, 9(3), 88-93. DOI: 10.12691/wjce-9-3-4
Pub. Date: November 07, 2021
2747 Views18 Downloads
Solving Chemical Equilibria in Titrimetry with the Inclusion of Ionic Strength Using OCTAVE and EXCEL
Original Research
Although Volumetric Analysis is one of the most widely used analytical techniques, there is limited published work on the use of computer software for simulation. In the few reports found in the literature, simplifications are often made for data treatment, due to the complexity of the equilibria involved. This work reports the application of a previously published methodology for calculating the concentration of chemical species, in multi-equilibrium problems, to simulate titration curves which describe the successive changes experienced in the solutions that are titrated. Two examples are solved with the help of the fsolve function in the open source computer programming language OCTAVE, and with the Solver tool in the EXCEL spreadsheet. Given that both the proposed methodology and the two computational platforms are capable of addressing complex systems without the need for simplifications, three important factors related with titrations can be considered: the behavior of the chemical indicator, the concurrence of collateral equilibria that can significantly affect the main titration reaction, and the effect of the ionic strength to explain deviations from ideality.
World Journal of Chemical Education. 2021, 9(3), 81-87. DOI: 10.12691/wjce-9-3-3
Pub. Date: October 24, 2021
6046 Views17 Downloads
Spectrophotometric Investigation of Complexation of Ferrous Ion with 3,5-Dintrosalicylic Acid
Original Research
The determination of stoichiometry and stability constant of metal-ligand complex holds great significance for chemical, physical, environmental and biological studies. In the present work, the stoichiometric ratio and stability constant of iron complex of 3,5-dinitrosalicylic acid was determined using Job’s method of continuous variation. Job’s method can be easily applied to investigate a wide range of colored complexes including mononuclear as well as polynuclear complexes of various species, therefore showing its usefulness for practical application in undergraduate University curriculum. The stoichiometry of the major complex formed was determined to have a 1:1 ratio of Fe+2 and 3,5-dinitrosalicylic acid. Stability constant value was determined and found to be 3 x 105. The resulting high stability of the complex can be attributed to resonance stabilization of metal-ligand П-bonding electron density. From the thermodynamic parameter, the negative value of overall change in Gibb’s free energy shows the complex formation between Fe+2 and 3,5-dinitrosalicylic acid is spontaneous and feasible.
World Journal of Chemical Education. 2021, 9(3), 77-80. DOI: 10.12691/wjce-9-3-2
Pub. Date: September 07, 2021
2805 Views2 Downloads
Experiment to Teach Multiple Melting Phenomena in Semicrystalline Polymers Using Differential Scanning Calorimetry
Original Research
This article describes a laboratory experiment used to investigate the phenomenon of multiple melting in polymers. The experiment is aimed at the level of senior undergraduate chemistry students able to carry out the investigation in a research-style approach, working together in small groups. The experiment highlights characteristic thermal behavioral differences between polymers and small organic molecules. It demonstrates that shifts in observed melting temperature upon heating are typically due to inherent metastability of the polymer system and not to impurities in the sample, for example. Differential scanning calorimetry is used to demonstrate and explore this fundamental yet contemporary subject of polymer melting, using a well-known and commercially available polymer, isotactic polystyrene. Effects of thermal history of the sample, including crystallization temperature and crystallization time, as well as analysis conditions including heating rate, on the melting point of the polymer solid are each investigated. The experiment provides a hands-on example of structure-property relationships in polymer science.
World Journal of Chemical Education. 2021, 9(3), 68-76. DOI: 10.12691/wjce-9-3-1
Pub. Date: September 03, 2021
6761 Views19 Downloads