12.7. What Are the Important Polymerization Reactions of Ethylene and Substituted Ethylenes?, 370
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Preparation of Conducting Polymers by Electrochemical Methods and Demonstration of a Polymer BatteryHiromasa Goto, Hiroyuki Yoneyama, Fumihiro Togashi, Reina Ohta, Akitsu Tsujimoto, Eiji Kita, and Ken-ichi Ohshima The electrochemical polymerization of aniline and pyrrole, and demonstrations of electrochromism and the polymer battery effect, are presented as demonstrations suitable for high school and introductory chemistry at the university level. Goto, Hiromasa; Yoneyama, Hiroyuki; Togashi, Fumihiro; Ohta, Reina; Tsujimoto, Akitsu; Kita, Eiji; Ohshima, Ken-ichi. J. Chem. Educ.2008, 85, 1067.
Aromatic Compounds |
Conductivity |
Electrochemistry |
Materials Science |
Oxidation / Reduction |
Polymerization
Thermal Analysis of PlasticsTeresa D'Amico, Craig J. Donahue, and Elizabeth A. Rais Students interpret previously recorded scans generated by differential scanning calorimetry and thermal gravimetric analysis to investigate a polypropylene dog bone, a polyethylene terephthalate pop bottle, the plastics in automobile head- and taillights, fishing line and a tea bag, and the rubber tread of an automobile tire. D'Amico, Teresa; Donahue, Craig J.; Rais, Elizabeth A. J. Chem. Educ.2008, 85, 404.
Materials Science |
Polymerization |
Thermal Analysis
Chemical Bonding Makes a Difference!Mary Harris This report describes a PowerPoint presentation that shows how a small difference in bonding can result in a drastic change in the properties of a material. Harris, Mary. J. Chem. Educ.2006, 83, 1435.
BIODEGRADABLE PLASTICSAmperegrine57 A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Polymerization |
Green Chemistry
Molecular Models of Antioxidants and RadicalsWilliam F. Coleman This month's featured molecules come from the paper by John M. Berger, Roshniben J. Rana, Hira Javeed, Iqra Javeed, and Sandi L. Schulien (1) describing the use of DPPH to measure antioxidant activity. DPPH was one of the featured molecules in September 2007 (2) and the basics of antioxidant activity were introduced in last month's column (3). In addition, some of the other molecules in the paper are already in the featured molecules collection (4). The remaining structures in the Figure 1 and Table 1 of the paper have been added to the collection. All structures have been optimized at the 6-311G(D,P) level. These molecules suggest a number of possible student activities, some reminiscent of previous columns and some new. (R,R,R)-α-tocopherol is one of the molecules in the mixture that goes by the name vitamin E. These molecules differ in the substituents on the benzene ring and on whether or not there are alternating double bonds in the phytyl tail. In (R,R,R)-α-tocopherol the R's refer to the three chiral carbon atoms in tail while α refers to the substituents on the ring. (R,R,R)-α-Tocopherol is the form found in nature. An interesting literature problem would be to have students learn more about the vitamin E mixture and the differing antioxidant activity of the various constituents. Additionally they could be asked to explore the difference between the word natural as used by a chemist, and "natural" as used on vitamin E supplements. Can students find regulations governing the use of the term "natural"? Can they suggest alternative legislation, and defend their ideas? If students read about vitamin C they will discover that only L-ascorbic acid is useful in the body. It would be interesting to extend the experiment described in the Berger et al. paper (1) to include D-ascorbic acid. How do the antioxidant abilities of the enantiomers, as determined by reaction with DPPH compare? Is this consistent with the behavior in the body? Why or why not? Berger et al. mention two other stable neutral radicals, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and Fremy's salt. In a reversal from the use of stable radicals to measure antioxidant properties, these two molecules have proven to be very versatile oxidation catalysts in organic synthesis, and would make a rich source of research papers for students in undergraduate organic courses.
