On the Web edited by
JCE Featured Molecules
William F. Coleman Wellesley College Wellesley, MA 02481
Molecular Models of Products and Reactants from Suzuki and Heck Syntheses April Featured Molecules 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-
Computed Charge on Carbon Atom
1.0
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 (Figure 2) 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. Literature Cited 1. Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P. J. Chem. Educ. 2008, 85, 555–557.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2008/Apr/abs592.html Full text (HTML and PDF) with links to cited URLs and JCE articles Supplement
Find “Molecular Models of Products and Reactants from Suzuki and Heck Syntheses” in the JCE Digital Library at http://www.JCE.DivCHED.org/JCEWWW/Features/ MonthlyMolecules/2008/Apr/.
The 9 molecules added to the collection this month are: phenylboronic acid and 4-phenylphenol (from the Suzuki synthesis of 4-phenylphenol) diflunisal and felbinac (representative biaryl non-steroidal anti-inflammatory drugs) acrylic acid, 4-iodoacetophenone, and (E)-4-acetylcinnamic acid (from the Heck synthesis of (E)-4-acetylcinnamic acid) oximidine II (example of a Suzuki synthesis) boron trianion
y = ź8.0876x ź 91.229 R2 = 0.9648
0.5
(E )-4-acetylcinnamic acid
0.0
Ľ0.5 Ľ11.40
Ľ11.35
Ľ11.30
Ľ11.25
Ľ11.20
4-phenylphenol
MO Energy of Carbon 1s Orbital / Eh Figure 1. The relationship between computed charge on carbon atoms and the energies of those carbon 1s orbitals in a molecular orbital calculation (HF/631-G(d)).
592
Figure 2. Two of the nine molecules featured this month. Manipulable Jmol versions of these and many other molecules are available at http:// www.JCE.DivCHED.org/JCEWWW/Features/MonthlyMolecules/.
Journal of Chemical Education • Vol. 85 No. 4 April 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
