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ERIC Number: EJ941056
Record Type: Journal
Publication Date: 2011-Aug
Pages: 7
Abstractor: As Provided
Reference Count: 10
ISBN: N/A
ISSN: ISSN-0021-9584
Dehydration of 2-Methyl-1-Cyclohexanol: New Findings from a Popular Undergraduate Laboratory Experiment
Friesen, J. Brent; Schretzman, Robert
Journal of Chemical Education, v88 n8 p1141-1147 Aug 2011
The mineral acid-catalyzed dehydration of 2-methyl-1-cyclohexanol has been a popular laboratory exercise in second-year organic chemistry for several decades. The dehydration experiment is often performed by organic chemistry students to illustrate Zaitsev's rule. However, sensitive analytical techniques reveal that the results do not entirely corroborate with Zaitsev's rule. Previous reports pertaining to this experiment have been limited by two factors: (i) it is difficult to separate 3- and 4-methyl-1-cyclohexene on a standard gas chromatography (GC) column and (ii) methods of accurate detection, identification, and quantification of trace minor products have been lacking. The current study uses gas chromatography--electron impact mass spectrometry (GC-MS) and quantitative nuclear magnetic resonance (qNMR) to identify and quantify not only the putative 1-, 3-, and 4-methyl-1-cyclohexene products but also several minor products such as methylenecyclohexane and ethylidenecyclopentane. Performing the dehydration with a single diastereomer of 2-methyl-1-cyclohexanol reveals a striking difference between the product distributions associated with cis and trans isomers. Some evidence continues to point towards an E2-like mechanism whereas other evidence, such as the presence of methylcyclohexene dimers in the still pot, points towards E1 carbocation intermediates. (Contains 2 tables, 5 figures, and 6 schemes.)
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail: eic@jce.acs.org; Web site: http://pubs.acs.org/jchemeduc
Publication Type: Journal Articles; Reports - Research
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A