|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
2001
>
April
> |
|
In the Laboratory
|
|
|
|
Diastereoselective Synthesis of (+/-)-1,2-Diphenyl-1,2-propanediol. A Discovery-Based Grignard Reaction Suitable for a Large Organic Lab Course
|
James A. Ciaccio, Roxana P. Bravo, Antoinette L. Drahus, John B. Biggins, Rosalyn V. Concepcion, and David Cabrera
Department of Chemistry, Fordam University, Bronx, NY 10458
|
|
April 2001
Vol. 78 No. 4
p. 531
|
|
|
|
|
|
|
| Abstract |
|
We have developed an undergraduate organic laboratory experiment that probes the diastereoselectivity of the reaction between a Grignard reagent and a common, inexpensive a-chiral ketone. Students isolate a single diastereomer of (+/-)-1,2-diphenyl-1,2-propanediol by treatment of (+/-)-benzoin with MeMgI. Since the mp ranges of the two possible diol diastereomers differ by 10 °C, the reaction's diastereoselectivity can be established by mp determination alone, and it can be rationalized by the preferential addition of MeMgI to the least sterically hindered face of the carbonyl group in a rigid, five-membered cyclic intermediate (the "Cram chelate model"). This experiment is an interesting alternative to traditional Grignard experiments, is operationally straightforward and easily performed in large lab courses, and introduces students to p-facial discrimination by having them establish the stereochemical course of kinetically controlled nucleophilic addition to a carbonyl.
|
| Supplement |
Background material, detailed instructions for the experiment, and sample spectra are available.
|
 Contents |
JCE2001p0531W.doc (MS Word 97/98)
|
| Download |
|
|
| More Information |
Citation |
Ciaccio, James A.; Bravo, Roxana P.; Drahus, Antoinette L.; Biggins, John B.; Concepcion, Rosalyn V.; Cabrera, David. J. Chem. Educ. 2001 78 531.
|
Keywords |
Inquiry-Based / Discovery Method; Laboratory Instruction; Mechanisms; Organic Chemistry; Organic Synthesis; Organometallics; Stereochemistry
|
History |
Created:
Last Updated: |
March 2, 2001
August 31, 2005
|
|
|
|
|
|
| Home > JCE Print > Journal of Chemical Education > Issues >
2001
>
April
> Page
531
|
|
|
| JCE HS CLIC |
|
Our Secondary School editors work hard to distill all the JCE materials to produce a fraction of particular interest to high school teachers. We call it CLIC.
|
| Contributions Welcome |
| JCE welcomes your submission |
| Advertisers |
| In recent years we have worked hard to better match our advertisers with our readers. When shopping for chemistry education materials, visit our advertisers' WWW sites first. |
| Be An Ambassador |
| Take JCE along on your outreach missions. Copies of the Journal, guest access to JCE Online, our publications catalog, and more are available for your participants. |
|
