Chem 353-14

Chem 353-14 - 6. Why is it more effective to perform an...

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Post Lab Questions – Reduction of a Ketone 1. Draw all the structures of the isomeric alcohols (C 5 H 12 O) that can be prepared by reduction of a ketone using sodium borohydride? 2. Circle all the structures from the previous question that present diastereotopic hydrogens, and box any structures that present enantiotopic hydrogens. 3. Take the only circled achiral structure from the first question and draw two wedge and dash structures that clearly demonstrate that the diastereotopic hydrogens are not equivalent using deuterium to substitute for hydrogen. Label the stereogenic centers either R or S. 4. Take the only boxed structure from the first question and draw two wedge and dash structures that clearly demonstrate a pair of enantiotopic hydrogens that are equivalent using deuterium to substitute for hydrogen. Label the stereogenic center(s) either R or S. 5. Answer question # 1 at the end of the reading for technique 11.
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Unformatted text preview: 6. Why is it more effective to perform an extraction with several small portions of solvent as opposed to one large portion of solvent of equal volume? 7. Answer question # 6 at the end of the reading for technique 19. 8. (Complete your cyclohexanol spectral analysis before proceeding.) Below is the 1 H NMR spectrum for cis-1,3,5-cyclohexanetricarboxylic acid. Draw the structure in the most stable chair conformation then label and assign all nonequivalent hydrogens using your analysis of cyclohexanol as a guide. 9. (Chem 354 only) Explain why the peak centered at 2.1ppm appears as a doublet. Does your explanation confirm that equatorial hydrogens are more deshielded than axial hydrogens as in the reference molecule provide for cyclohexanol? (Hint: Read technique 21.9, and understand how to apply Figure 21.28 in the techniques manual; your argument should include relevant dihedral angles.)...
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