| Other Resources: 17 results |
Molecular Models of Reactants and Products from an Asymmetric Synthesis of a Chiral Carboxylic Acid William F. Coleman
Our JCE Featured Molecules for this month come from the paper by Thomas E. Smith, David P. Richardson, George A. Truran, Katherine Belecki, and Megumi Onishi (1). The authors describe the use of a chiral auxiliary, 4-benzyl-2-oxazolidinone, in the synthesis of a chiral carboxylic acid. The majority of the molecules used in the experiment, together with several of the pharmaceuticals mentioned in the paper, have been added to our molecule collection. In many instances multiple enantiomeric and diastereomeric forms of the molecules have been included. This experiment could easily be extended to incorporate various aspects of computation for use in an advanced organic or integrated laboratory. Here are some possible exercises using the R and S forms of the 4-benzyl-2-oxazolidinone as the authors point out that both forms are available commercially. Calculation of the optimized structures and energies of the enantiomers at the HF/631-G(d) level using Gaussian03 (2) produces the results shown in Table 1. Evaluation of the vibrational frequencies results in no imaginary frequencies and the 66 real frequencies are identical for the two forms. Examination of the computed IR spectra also shows them to be identical. Additionally, the Raman and NMR spectra can be calculated for the enantiomers and compared to experimental values and spectral patterns. A tool that is becoming increasingly important for assigning absolute configuration is vibrational circular dichroism (VCD). Although the vibrational spectra of an enantiomeric pair are identical, the VCD spectra show opposite signs, as shown in Figure 1. One can imagine a synthesis, using an unknown enantiomer of the chiral auxiliary, followed by calculations of the electronic and vibrational properties of all of the intermediates and the product, and determination of absolute configuration of reactants and products by comparison of experimental and computed VCD spectra. Using a viewer capable of displaying two molecules that can be moved independently, students could more easily visualize the origin of the enantiomeric preference in the reaction between the chelated enolate and allyl iodide.
Green Chemistry
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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
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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
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Sorting recyclable plastics by density Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Physical Properties |
Green Chemistry
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Synthesis of Biodiesel Fuel Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Stoichiometry |
Green Chemistry
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BIODEGRADABLE PLASTICS Amperegrine57
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Polymerization |
Green Chemistry
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Bisphenol A Rrizor
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Polymerization |
Green Chemistry
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A Greener Bleach Stacy Gates
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Oxidation / Reduction |
Green Chemistry
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Using Chemical Equations in Environmental Chemistry and Green Chemistry Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Chemometrics |
Green Chemistry
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Hydrogen Powered Bicycles Run on Water Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Stoichiometry |
Green Chemistry
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Atom Efficiency and the 2006 Presidential Green Chemistry Award Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Stoichiometry |
Green Chemistry
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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
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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
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Water on Mars Ed Vitz
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Thermodynamics |
Astrochemistry |
Atmospheric Chemistry
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Air-Science for Kids American Chemical Society
ACS Science for Kids activities exploring the chemistry of air.
Atmospheric Chemistry |
Applications of Chemistry |
Gases
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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
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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
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