Final Project Spring 2011: Part III

The second synthesis project (performed by a fourth of the class) started out with a reaction we had done a few weeks before. The oxidation of cyclohexanol with household bleach was the lead-off reaction. This was followed by the addition of phenylmagnesiumbromide Grignard reagent to the cyclohexanone. We added a rather large excess of Grignard reagent in the event that there was some cyclohexanol contamination from the first reaction product. (In the previous experiment, a significant amount of unreacted cyclohexanol was found in some student’s product mixtures.) The second product, 1-phenylcylohexanol tended to be a liquid even though the literature melting point is 58-62 (chemexper). Possibly, some dehydration occurs during the aqueous acid workup of the Grignard reaction. The tertiary alcohol from the second reaction was then dehydrated in the presence of phosphoric acid. The final product, 1-phenylcyclohexene, is commercially available. All of the products for this reaction sequence could be analyzed by GC-FID. Gas Chromatography evidence suggests that a positional isomer of 1-phenylcyclohexene is present in the product mixture.

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