8.2 Preparation of Alkynes: Elimination Reactions of Dihalides
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Reactions: Acetylene Preparation of acetylene and the reaction of chlorine with acetylene are demonstrated. An antique carbide lamp is also demonstrated.
The Iodochlorination of Styrene: An Experiment That Makes a DifferenceR. Gary Amiet and Sylvia Urban This purpose of this laboratory exercise is to determine the various substitution and elimination products generated in the iodochlorination of styrene and their relative proportions through the application of mechanistic principles and a basic knowledge of GCMS and NMR. Amiet, R. Gary; Urban, Sylvia. J. Chem. Educ.2008, 85, 962.
Alkenes |
Constitutional Isomers |
Gas Chromatography |
Instrumental Methods |
Mass Spectrometry |
Mechanisms of Reactions |
NMR Spectroscopy |
Synthesis |
Student-Centered Learning
Organic Reactions Involving Bromine: Puzzles for the Organic LaboratorySarita I. McGowens and Ernest F. Silversmith Five puzzles for the organic chemistry laboratory are described. All involve bromine, which is generated in a safe, convenient way that makes it possible to control the amount of bromine precisely. Three of the puzzles involve orientation in electrophilic aromatic substitution, one is a determination of the stereochemistry of addition to alkenes, and the other one looks at the possibility of dehydrohalogenation following addition. McGowens, Sarita I.; Silversmith, Ernest F. J. Chem. Educ.1998, 75, 1293.
NMR Spectroscopy |
Synthesis |
Stereochemistry |
Mechanisms of Reactions
A series of synthetic organic experiments demonstrating physical organic principlesSayed, Yousry; Ahlmark, Chris A.; Martin, Ned H. The sequence of reactions described here incorporates several common synthetic organic transformations involving alkenes, alcohols, alkyl halides, and ketones that demonstrate some important principles of physical organic chemistry. Sayed, Yousry; Ahlmark, Chris A.; Martin, Ned H. J. Chem. Educ.1989, 66, 174.
Unsaturated HydrocarbonsEd Vitz, John W. Moore A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Alkenes |
Alkynes
Percent YieldEd Vitz, John W. Moore A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Synthesis
Molecular Models of Products and Reactants from Suzuki and Heck SynthesesWilliam F. Coleman Our Featured Molecules this month come from the paper by Evangelos Aktoudianakis, Elton Chan, Amanda R. Edward, Isabel Jarosz, Vicki Lee, Leo Mui, Sonya S. Thatipamala, and Andrew P. Dicks (1), in which they describe the synthesis of 4-phenylphenol using an aqueous-based Suzuki reaction. The authors describe the various ways in which this reaction addresses concerns of green chemistry, and point out that their product bears structural similarity to two non-steroidal anti-inflammatory drugs (NSAIDs), felbinac and diflunisal. A number of molecules from this paper and its online supplemental material have been added to the Featured Molecules collection. Students will first notice that the aromatic rings in the molecules based on a biphenyl backbone are non-planar, as is the case in biphenyl. If they look carefully at diflunisal, they will notice that the carbon atoms are in a different chemical environment. One way in which to see the effect of these differing environments is to examine the effect of atom charge on the energies of the carbon 1s orbitals. Figure 1 shows this effect using charges and energies from an HF/631-G(d) calculation. A reasonable question to ask students would be to assign each of the data points to the appropriate carbon atom. As an extension of this exercise students could produce similar plots using different computational schemes. Are the results the same; are they parallel. This would be a useful problem when dealing with the tricky question of exactly what is meant by atom charge in electronic structure calculations. Students with more expertise in organic chemistry could explore extending the synthesis of 4-phenylphenol to produce more complex bi- and polyphenyl-based drugs. This may well be the first time that they have seen coupling reactions such as the Suzuki and Heck reactions. Students in introductory and non-science-major courses might well find the NSAIDs to be an interesting group of molecules, and could be asked to find information on the variety of molecules that display the anti-inflammatory properties associated with NSAIDs. Do they find structural similarities? Are there various classes of NSAIDs? Are they familiar with any of these molecules? Have they taken any NSAIDs? If so, for what reason? Is there any controversy about any of the NSAIDs? As with all of the molecules in the Featured Molecules collections, those added this month provide us with a number of ways of showing students the practical relevance of what they sometime see only as lines on a page. Molecules do matter.
