Experiment 5B: Ketone Reduction
Objective: Using sodium borohydride as a reducing agent, the ketone 4-tert-butylcyclohexane is reduced to its corresponding alcohol. It is purified through extraction techniques to give the cis and trans diasteromer products. Procedure: The procedure was followed as outlined in Mayo’s book for Experiment 5B with the following modifications: 1.
Reagents and Equipment – The reaction will be on a scale of 2X what is described in the text. 2.
Reagents and Equipment – The progress of the reaction will be followed by TLC as directed in the Reaction Conditions section. Glass backed TLC plates will be created with the following three spots: Ketone Standard/Co-Spot/Crude Reaction Mixture. Prepare the TLC plate while the reaction is being set up. To the initial solution of 4-tert-butylcyclohexane in methanol, before adding the reducing solution, insert a TLC capillary. Use this sample as your ketone standard. Do NOT stop the reaction before checking the progress by TLC. If the reaction is not complete, add another portion of the reducing solution. 3.
Isolation of Product – All other amounts specified in this section should be followed without doubling. 4.
Isolation of Product – Substitute 1.0 mL of cold 3.0 M HCl for 1.0 mL of cold 0.1 M HCl. 5.
Purification and Characterization – Will not obtain an NMR spectrum. Reaction Scheme:
Data and Results:
Mp (degrees C)
Bp (degrees C) 4-tert-butylcylcohexane
47 – 50
Sodium Borohydride reducing solution
*NOTE: As I was condensing my product in the sand bath it “popped” and there was no more final product in my vial. Therefore I was not able to do a final analysis and I am using Mike Mariani’s data in my report.
Crude product was solid and white in color.
TLC spots were dark purple for both the ketone standard and co-spot. The spot for the crude reaction mixture...
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