Oxidation of Benzoin and Reduction of Benzil

 

1. Write a reaction in standard organic chemistry form for the oxidation of benzoin to benzil.

 

2. (a) Write a half-reaction using the ion electron method showing the oxidation half-reaction

for benzoin going to benzil.

(b) Write a half-reaction using the ion electron method showing the reduction half-reaction.

Assume that HNO3 is reduced to NO2.

(c) Add the half-reactions in a and b to give a balanced overall equation.

 

3. Prepare a table of reactants (and products) in the usual fashion for the oxidation of benzoin

to benzil.

 

4. Provide a flow chart of the procedure you carried out to prepare benzil.

 

5. Calculate the theoretical yield of benzil expected.

(Always show set-ups for all calculations.)

 

6. Weigh the dried product, report the mass of product isolated and calculate the percentage

yield. Run an IR of the dried product and submit it with your report. If IR is not good, run a

melting point instead. Save the product for use in the next experiment, the Reduction of

Benzil.

 

 

7. Write a reaction in standard organic chemistry form for the reduction of benzil to

hydrobenzoin. Do not concern yourself with the stereochemical consequences in this

equation. (i.e. Do not be specific about the absolute configuration about the two stereogenic

centers produced.)

 

8. Write a mechanism for the reduction of the first carbonyl group. You may assume that a

hydride ion, :H is the attacking nucleophile and H+ is the electrophile.

 

9. Prepare a table of reactants (and products) in the usual fashion for the reduction of benzil to

hydrobenzoin. If you used your product and did not weigh your product in step 6, assume

that you began with the theoretical yield of benzil from the first reaction. If you used benzyl

from the stockroom, use the weight of benzil you weighed out.

 

10. Provide the stepwise procedure you carried out to prepare hydrobenzoin.

 

11. Calculate the overall theoretical yield of hydrobenzoin expected (starting from benzoin, if

you used all your product, or the amount of benzil you weighed out, if you did not use your

product).

 

12. Report the mass of product isolated and calculate the overall percentage yield.

 

13. Report the literature melting point and your experimental melting point.

 

14. Run an IR of your product. Submit the IR and a sample of your product along with your

report.

 

15. Starting with benzil, it is possible to produce meso-hydrobenzoin and d,l-hydrobenzoin.

(a) Show how both of these can form.

(b) Upon attempted purification, it is theoretically possible to isolate two fractions.

What is in each? Is either optically active? Explain.