ERIC Number: EJ936776
Record Type: Journal
Publication Date: 2011-May
Pages: 3
Abstractor: As Provided
ISBN: N/A
ISSN: ISSN-0021-9584
EISSN: N/A
Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography-Mass Spectroscopy (GC-MS)
Clennan, Malgorzata M.; Clennan, Edward L.
Journal of Chemical Education, v88 n5 p646-648 May 2011
Dehydrations of "cis"- and "trans"-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78-80 [degrees]C as a function of time and the products were identified by gas chromatography-mass spectroscopy (GC-MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and 1-ethylcyclopentene, as well as the alcohols, 1-, 3-, and 4-methylcyclohexanols, and residual starting material. Independent reactions under identical conditions of the pure "cis"- and"trans"-2-methylcyclohexanol isomers, 1-, 3- and 4-methylcyclohexanol were also carried out. These reactions reveal that the "cis"-isomer reacts predominately to form 1-methylcyclohexene whereas the "trans"-isomer reacts to give a complicated mixture consisting of the isomeric 1-, 3-, and 4-methylcyclohexanols, 1-, 3-, and 4-methylcyclohexenes, and the ring contraction product, 1-ethylcyclopentene. In the experiment, each student carries out a dehydration of the "cis"- and "trans"-2-methylcyclohexanol mixture or of one of the pure isomers and the results from the GC-MS analyses of the whole class are pooled. The analysis reinforces lecture material and provides an appreciation of the complexity of elimination-dehydration reactions that proceed via carbocation intermediates and can undergo intricate rearrangements such as hydride and alkyl shifts. The reaction procedure is straightforward and the GC-MS analysis simple enough so it can easily be used in the first semester of undergraduate organic chemistry laboratory. (Contains 2 tables, 1 figure, 1 scheme, and 3 notes.)
Descriptors: Spectroscopy, Organic Chemistry, Science Laboratories, College Science, Scientific Principles, Undergraduate Study
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 - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A