exp2 - Justin Barry Professor Bill Dailey Chemistry 502...

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Justin Barry Professor Bill Dailey Chemistry 502 Experiment #5, Alkenes: Preparation, Reactions, and Properties Experimental Organic Chemistry: A Miniscale and Microscale approach by Gilbert and Martin, Section 10.1-10.3 8-7-06 TA: Mike Hall INTRODUCTION: Alkenes are very important reagents in the production of the Diels-Alder reaction and in the dehydration of alcohols. Using a strong acid as a catalyst, one can dehydrate an alcohol to produce an alkene. However, several alkenes can be produced depending of the thermodynamic stability of the products. The thermodynamic stability can be calculated experimentally using Gibbs-free energy and can be compared to the energy calculated in Chem3D. In this experiment, we will convert 2-methylcyclohexanol to a mixture of 1-methyl-and 3-methylcyclohexene. The double bond is more selective to one product than another and will be proven with the Gas- Liquid chromatograph. The purpose of this lab is to verify that the more substituted carbon will receive the double bond at a greater percentage in this experiment. A fractional distillation will be used to eliminate the hydroxide and drive the reaction towards the products, incorporating LaChatlier’s principle. PROCEDURE Place a small magnetic stirbar and 5-mL of the mixture, cis $ trans 2-methylcyclohexanol in a 25-mL round bottom flask, add to this 3-mL of 9M sulfuric acid. Adjust for even stirring rate and distill the mixture through a fractional distillation setup. Use thermowell heater as the heat source. Use your 10-mL graduated cylinder in an ice- water bath as your receiver. Make a record of the volumes and temperatures. Collect distillate at a rate of one drop every one or 2 seconds. If, at the end of the distillation, the rate of distillate becomes very slow and if you don’t have 3-4-mL of the organic olefin mixture in your distillate, add 3-mL of water to the flask and resume the distillation.
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Transfer the distillate to a small separatory funnel and wash the organic product successively with 10-mL of water, 10-mL of 3 N aqueous sodium hydroxide solution, and 10-mL of saturated sodium chloride solution. Drain the organic layer into a 25-mL Erlenmeyer flask and dry it over a small amount of anhydrous calcium chloride. After swirling for a few minutes, decant the solution away from the CaCl 2 using a Pasteur pipet to transfer the solution to a tared vial. (The solution should be clear) Weigh and calculate the % yield for the reaction. Do not distill. Test the product mixture for unsaturation with the Bromine $ Baeyer Test. Carry out the two control tests. One on cyclohexane (which should be negative) and one on cyclohexene (which will be positive). Use test tubes for the tests. The Baeyer test will form brown precipitate for a positive test. Analyze your product by chromatography.
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This note was uploaded on 04/23/2010 for the course CHEM CHEM2220 taught by Professor Andreana during the Fall '10 term at Wayne State University.

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exp2 - Justin Barry Professor Bill Dailey Chemistry 502...

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