Expt #4 - Oxidation of Borneol and Reduction of Camphor

Reading Assignment - Pavia, Expt 35. Technique 9. Technique 35 (see the part on obtaining IR spectra of solid samples).

Prelab - Make sure you include the moles to be used of all reactants and the theoretical yields of the products. Make sure to bring your laptop to this lab.

Overview - You will oxidize a chiral alcohol, borneol (endo-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol) to the corresponding ketone, camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) using sodium hypochlorite. TLC will be used to make sure the reaction is complete before purifying the camphor product and characterizing by IR and mp determination. This ketone will then be reduced back to an alcohol using NaBH₄ and we will observe the stereoselectivity of this reaction using ¹H NMR.  Molecular modeling will be used to help explain the result.

Procedure - We are carrying out Experiment 35A, B, C  in Pavia on pp 288-301 including  the optional molecular modeling on p 301. The following are modifications and other notes to keep in mind when carrying out the procedures. 

    1. The apparatus for Part A calls for an air condenser. Use a regular jacketed condenser but do not connect water tubes or run water through as one normally would do. 

    2. Use the dry film method (p 838) for the IR of the camphor product.

    3. I recommend using a screw cap vial in place of the 10-mL Erlenmeyer flask in the isolation of the first product.

    4. TLC procedures will be similar to those specified in Pavia. However, plan on using UV light rather than iodine for the visualization. Also try to halve the volumes of the reaction solution and CH₂Cl₂ used to prepare the samples for TLC spotting. Use a very small test tube for this extraction. Check the reaction after the recommended reaction time and if it does not appear finished add more NaOCl(aq) and allow it to react 15 minutes more.

    5. We will not obtain the IR spectrum or run a GC of the final product. Instead a mp and ¹H NMR spectrum will suffice. 

Report:

Results. Make sure to integrate the NMR spectrum of the final product as described in the Part C procedure on p 295  and present these results, as well as the Camphor TLC, IR and mp data, in your results tables.

Assigned questions. Answer questions  2, 3, and 5 on pp 301-302  of Pavia. 

Conclusions. Present and discuss the mechanism of each reaction carried out. Also Include discussions of...

• the yields obtained in each reaction and reasons for loss of yield
• the completeness of the first reaction as indicated by TLC
• the purity of the camphor product of the first step as indicated by IR and mp
• interpretation of the IR spectrum of camphor including peak assignments and a comparison to the literature spectrum
• the stereoselectivity of the hydride reduction step (part C - ¹H NMR results) including an explanation based on the molecular modeling exercise