NotesFAQContact Us
Collection
Advanced
Search Tips
Peer reviewed Peer reviewed
Direct linkDirect link
ERIC Number: EJ820872
Record Type: Journal
Publication Date: 2007-Nov
Pages: 3
Abstractor: As Provided
Reference Count: 25
ISBN: N/A
ISSN: ISSN-0021-9584
Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions
Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung
Journal of Chemical Education, v84 n11 p1819-1821 Nov 2007
Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free energy relationship. Substituent electronic effects were studied by competition experiments and the product ratios were determined by gas chromatography. Hammett plots were constructed from the relative rates, and the reaction constants (p) obtained in varying the substituents at the para position of benzaldehyde and acetophenone were 3.09 and 1.59, respectively. The reaction rates were found to be more sensitive to the substituents on benzaldehyde. The positive reaction constants suggested that nucleophilic addition (the first step) is the rate-determining step as the reaction rates were enhanced by increasing the electrophilicity of benzaldehyde as well as the acidity of the [alpha]-H of acetophenone. (Contains 1 scheme, 3 tables and 2 figures.)
Division of Chemical Education of the American Chemical Society. Subscription Department, P.O. Box 1267, Bellmawr, NJ 08099-1267. Tel: 800-691-9846; Tel: 856-931-5825; Fax: 856-931-4115; e-mail: jchemed@egpp.com; Web site: http://www.jce.divched.org
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education; Postsecondary Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A