TIGER

Other Resources: 16 results
Molecular Models of Antioxidants and Radicals  William 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.
Free Radicals |
Natural Products
Biologically Active Exceptions to the Octet Rule  Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Lewis Structures |
Free Radicals |
Vitamins
Exceptions to the Octet Rule  Ed Vitz, John W. Moore
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Lewis Structures |
Free Radicals |
Molecular Properties / Structure
Importance of Air  
Volume 03, issue 08 of a series of leaflets covering subjects of interest to students of elementary chemistry distributed in 1929 - 1932.
Atmospheric Chemistry
The Air  
Volume 05, issue 09 of a series of leaflets covering subjects of interest to students of elementary chemistry distributed in 1929 - 1932.
Atmospheric Chemistry
Molecular Models of Volatile Organic Compounds  William F. Coleman
This month's Featured Molecules come from the Report from Other Journals column, Nature: Our Atmosphere in the Year of Planet Earth, and the summary found there of the paper by Lelieveld et al. (1, 2) Added to the collection are several volatile organic compounds (VOCs) that are emitted by a variety of plants. The term VOCs is a common one in environmental chemistry, and is interpreted quite broadly, typically referring to any organic molecule with a vapor pressure sufficiently high to allow for part-per-billion levels in the atmosphere. Common VOCs include methane (the most prevalent VOC), benzene and benzene derivatives, chlorinated hydrocarbons, and many others. The source may be natural, as in the case of the plant emissions, or anthropogenic, as in the case of a molecule such as the gasoline additive methyl tert-butyl ether (MTBE).The oxidation of isoprene in the atmosphere has been a source of interest for many years. Several primary oxidation products are included in the molecule collection, although a number of isomeric forms are also possible (3).The area of VOCs provides innumerable topics for students research papers and projects at all levels of the curriculum from high-school chemistry through the undergraduate courses in chemistry and environmental science. Along the way students have the opportunity for exposure to fields such as epidemiology and toxicology, that may be new to them, but are of increasing importance in the environmental sciences. The MTBE story is an interesting one for students to discover, as it once again emphasizes the role that unintended consequences play in life. An exploration of the sources, structures, reactivity, health and environmental effects and ultimate fate of various VOCs reinforces in students minds just how interconnected the chemistry of the environment is, a lesson that bears repeating frequently.
Molecular Modeling |
Atmospheric Chemistry
Air  
Volume 04, issue 03 of a series of leaflets covering subjects of interest to students of elementary chemistry distributed in 1929 - 1932.
Atmospheric Chemistry |
Gases
Water on Mars  Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Thermodynamics |
Astrochemistry |
Atmospheric Chemistry
Air-Science for Kids  American Chemical Society
ACS Science for Kids activities exploring the chemistry of air.
Atmospheric Chemistry |
Applications of Chemistry |
Gases
Cannon (GCMP)  David M. Whisnant
H2 and Cl2 cannon: this is a resource in the collection "General Chemistry Multimedia Problems". In this problem we observe the reaction of hydrogen and chlorine and explore some related reactions. The reaction involves a radical mechanism initiated by light. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.
Photochemistry
Planet Earth  American Chemical Society
ACS Science for Kids activities and tests exploring applications of chemistry on Earth.
Atmospheric Chemistry |
Applications of Chemistry |
Water / Water Chemistry |
Geochemistry |
Plant Chemistry
Air-Solids, Liquids & Gases  American Chemical Society
ACS Science for Kids activities explore the properties of gases.
Atmospheric Chemistry |
Acids / Bases |
Reactions |
Applications of Chemistry |
Water / Water Chemistry |
Gases
Prophine and Protoporphyrin  William F. Coleman, Randall J. Wildman
The WebWare molecules this month are from the article "Photochemotherapy: Light-Dependent Therapies in Medicine" by Edward P. Zovinka and Danielle R. Suneri. The first is a simple porphine, illustrating the ubiquitous four-nitrogen macrocycle, while the second is the protoporphyrin found in heme systems.
Medicinal Chemistry |
Photochemistry
Photoelectric Effect  William F. Coleman
This is a series of simulations of aspects of the photoelectric effect. There is an animation of the experiment with four choices of incident radiation - low and high intensity "red", to represent low energy light and low and high intensity "blue" to represent higher energy light. Electron production is animated and there is an ammeter to simulate current flow. Additional simulations show the effect of light frequency and intensity. There is a link to a spreadsheet that allows students to choose a sample from among five metals. The spreadsheet includes several questions to be answered after working through the materials.
Photochemistry |
Quantum Chemistry |
Enrichment / Review Materials
Photochemical Oxidation of Bilirubin to Biliverdin  William F. Coleman
The Featured Molecules from September come from the article Solar Irradiation of Bilirubin: An Experiment in Photochemical Oxidation by F. M. Salih and A. E. Pillay.
Molecular Modeling |
Molecular Properties / Structure |
Photochemistry
Luminescent Molecular Thermometers  William F. Coleman
The Featured Molecules this month come from the paper "Luminescent Molecular Thermometers" by Uchiyama, Prasanna de Silva, and Iwai exploring the many ways that photophysical properties can be used as temperature probes. They introduce a variety of molecule types, many of them now in our molecule collection. Excited states play a central role in this paper and it provides an opportunity to introduce students to some excited state properties.
Molecular Modeling |
Molecular Properties / Structure |
Photochemistry