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  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > July  >
In the Laboratory
Regiospecific Epoxidation of Carvone: A Discovery-Oriented Experiment for Understanding the Selectivity and Mechanism of Epoxidation Reactions
Kendrew K. W. Mak, Y. M. Lai, and Yuk-Hong Siu
Department of Chemistry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, PRC
Cover
July 2006
Vol. 83 No. 7
p. 1058
Abstract
This article describes a discovery-oriented experiment for demonstrating the selectivity of two epoxidation reactions. Peroxy acids and alkaline H2O2 are two commonly used reagents for alkene epoxidation. The former react preferentially with electron-rich alkenes while the latter works better with α,β-unsaturated carbonyl compounds. The selectivity of these two reagents on carvone, a naturally occurring compound that contains both types of C=C bonds, was investigated. The product mixtures obtained from the two different reactions were analyzed by thin-layer chromatography and 1H NMR spectroscopy. Both of the reactions were found to be regiospecific. The selectivity was attributed to the roles played by the alkene C=C bonds, which act as a nucleophile in the peroxy acid epoxidation but as an electrophile in the alkaline H2O2 reaction. The discovery-oriented approach is aimed at strengthening students' knowledge of the relationship between the reaction selectivity and the mechanisms.
Supplement
Students' handout, instructors' notes, detailed experimental procedures, NMR, IR and mass spectra, and detailed interpretation of spectra are available.
*  Contents JCE2006p1058W.doc (Microsoft Word)
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*  Citation
 Mak, Kendrew K. W.; Lai, Y. M.; Siu, Yuk-Hong. J. Chem. Educ. 2006 83 1058.
*  Keywords
 Alkenes; Chromatography; Epoxides; Hands-On Learning / Manipulatives; Inquiry-Based / Discovery Learning; IR Spectroscopy; Laboratory Instruction; Mechanisms of Reactions; NMR Spectroscopy; Organic Chemistry; Second-Year Undergraduate; Synthesis; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 5/26/2006
5/31/2006
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