Student Polyester wants to synthesize triphenylmethanol by a condensation reaction between a ketone (benzophenone) and a Grignard reagent (phenylmagnesium bromide). Carefully she cleaned the 1.0-mL syringe with H2O just before the addition of the ethereal solution of benzophenone to the phenylmagnesium bromide. The syringe was not properly dried and had a copious quantity of H2O in it during the transfer of the ethereal benzophenone solution to the freshly prepared Grignard reagent. 1. Predict all three products of this experiment.
2. Why is it important that all the equipment used in the Grignard formation be completely dry?
3. Name the major undesired side-product formed in the Grignard reaction in this experiment in the absence of water.
4. You will perform the same experiment as Polyester following your handout procedure.
a. What is the purpose of adding hexane to the crude product obtained after evaporation of the ether?
b. What product would be formed if acetone were added to the Grignard reagent instead of benzophenone?
c. If you had leftover benzophenone in your sample, how would the product melting point be affected?
d. How can the IR spectrum be used to tell whether any leftover benzophenone was present in your product sample?