Question

In an experiment we used, Grignard reagent reacted with benzophenone, in a two stepped process in order to create triphenylmethanol

1. If you use excess Grignard reagent in this reaction, what contaminant would it yield after hydrolysis with HCl?
2. Would you expect this contaminant to be removed in the extraction step?

Answer 1

Grignard reagent reacts with benzophenone to give triphenylmethanol. But the use of an excess of the Grignard reagent gives biphenyl as the by-product after hydrolysis with HCl, as given below.

Extraction of biphenyl: After extracting the crude product from the reaction mixture, we use to get a mixture of triphenylmethanol and biphenyl. This crude product then dissolved in hexane or ether. Now biphenyl will only get dissolved in the ether or hexane while triphenylmethanol can be separated by filtration as the powder. Then the filtrate evaporates to give biphenyl.