The Synthesis of Alkenes: The Dehydration of Cyclohexanol

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The Synthesis of Alkenes: The Dehydration of Cyclohexanol
Adam Ohnmacht
CHEM 0330
Scott Caplan
10/30/12

Abstract: In Organic Chemistry, many different methods are used to synthesize organic compounds from various components. In this lab, cyclohexanol was dehydrated to cyclohexene through an elimination reaction. In order to separate the cyclohexene product from the cyclohexanol starting component, previously learned lab techniques such as extractions and simple distillation were used. The formation of the product was verified by performing a Bromine test as well as an analysis using IR Spectroscopy. A percent yield of 8.33% was obtained.
Introduction:
In an elimination reaction, two substituents are removed from a molecule in either a one or two-step mechanism. There is a removal of a leaving group and a proton to form alkenes. The proton is often called an alpha hydrogen, which is the hydrogen atom attached to the alpha carbon. Even though it is possible to lose any alpha hydrogen in an elimination reaction, the most substituted product is the major product, and the most substituted double bond will predominate. There are two types of elimination reactions: E1 and E2. Good leaving groups are needed in these two reactions. E2 reactions are a bimolecular concerted reaction, which means that it is a reaction involving two molecular entities and bonds are forming and breaking at the same time. The two steps in this reaction happen simultaneously in one transition step. For this reason, both the concentration of the substrate and the base are present in the rate law equation; rate = k[substrate][base]. In an E2 reaction, a strong base is used in order to deprotonate the molecule causing a transfer of the electron density to form a pi bond between two carbons. Examples of a strong base are KOH or OH-. A good leaving group is also required which includes I-, Cl-, and Br-. There are other good leaving groups aside from those previously



References: Huston, E., & Liu, C. (2011). CHEM 0330 Organic Chemistry I Laboratory Manual. Plymouth: Hayden-McNeil Publishing. Padias, A. Making the connections (2 ed.). Plymouth: Hayden-McNeil Publishing, The Chemical Database. (n.d.). HordeNet at the University of Akron. Nov. 3, 2012. Ull.chemistry.uakron.edu “Chemistry-Interpretation of Infrared Spectra.” Chem-custan. CSU Stanislaus, 01 05 1998. Web. 3 Nov. 2012. www.chem.csustan.edu/tutorials/infrared.htm.

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