15.5. What Is the Significance of Chirality in the Biological World?, 436
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Polarized Light and Organic Molecules Polarizing filters and the rotation of polarized light by chiral compounds are demonstrated and a polarimeter is shown. Several everyday objects are examined between polarizing filters.
Organic : IDChiralAtoms (20 Variations) Identify the chiral carbon atom(s), if any, in the following structure. The carbon atoms have been numbered for easier identification.
Frank Westheimer's Early Demonstration of Enzymatic SpecificityAddison Ault Reviews one of the most significant accomplishments of one of the most respected chemists of the 20th centurya series of stereospecific enzymatic oxidation and reduction experiments that led chemists to recognize enantiotopic and diastereotopic relationships of atoms, or groups of atoms, within molecules. Ault, Addison. J. Chem. Educ.2008, 85, 1246.
Asymmetric Synthesis |
Bioorganic Chemistry |
Catalysis |
Chirality / Optical Activity |
Enantiomers |
Enzymes |
Isotopes |
Nucleophilic Substitution |
Oxidation / Reduction |
Stereochemistry
The Preparation and Enzymatic Hydrolysis of a Library of EstersElizabeth M. Sanford and Traci L. Smith In this investigative case study, students work collaboratively to prepare and characterize a library of esters using Fischer esterification and alcoholysis of acid chlorides and their subsequent enzymatic hydrolysis by pig liver and orange peel esterases. Sanford, Elizabeth M.; Smith, Traci L. J. Chem. Educ.2008, 85, 944.
Drugs / Pharmaceuticals |
Enzymes |
Esters |
Industrial Chemistry |
IR Spectroscopy |
NMR Spectroscopy |
Synthesis |
Thin Layer Chromatography
The Resolution of Ibuprofen, 2-(4′-Isobutylphenyl)propionic AcidJames V. McCullagh In this experiment the over-the-counter pain reliever ibuprofen is resolved using (S)-(-)-a-phenethylamine as the resolving agent. This procedure has several key advantages over previous resolution experiments. McCullagh, James V. J. Chem. Educ.2008, 85, 941.
Properties of AlkanesEd Vitz, John W. Moore A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Chirality / Optical Activity
Collection of Chiral Drug, Pesticide, and Fragrance Molecular ModelsWilliam F. Coleman The article by Mannschreck, Kiessewetter, and von Angerer on the differential interactions between enantiomers and biological receptors (1) is the source for this month's Featured Molecules. Included in the molecule collection are all of the molecules described in the paper. In many instances we have included structures of multiple optical isomers of the same molecule so that students can not only see the forms that are active, but those that are less active, inactive, or act in an undesirable manner. These molecules will serve as good practice in determining optical configurations, and will also introduce additional forms of isomerism that students may be less familiar with than they are with R and S. Since multiple enantiomers and diastereomers are provided, students may use these molecules, together with an appropriate computational package, to verify that enantiomers have the same energy while diastereomers do not. The tuberculosis drug ethambutol provides an interesting case as both nitrogen atoms are also chiral as well as the two chiral carbon atoms. A calculation on a given structure will include the effect of that nitrogen chirality, although nitrogen inversion is expected to be quite rapid in this molecule. The conformations for the ethambutol molecules that are included here consider all four chiral atoms and are of the form (CNNC). A reasonable computational exercise would be to find the transition state for nitrogen inversion and the barrier height for that process. The supplemental material that is included with the featured article (1) includes a number of molecules that we will add to the collection as time permits. The result, including enantiomers and diastereomers, will be well over 200 additional molecules. A notice will appear in the JCE Featured Molecules column when this new set of molecules is available in JCE Online.
Chirality / Optical Activity |
Biosignaling
Stereochemistry TutorialNicola Burrmann Master the concepts organic stereochemistry with this interactive tutorial. It includes definitions, different three dimensional representations, assigning priorities to stereocenters, and determining the stereochemical relationship between molecules. Each section is followed by a question set that tests knowledge and understanding.
