2009 - instead of benzophenone we used 2, 3, and 4-methyl-1-cyclohexanone as ketones.
The reaction worked well.
Student Handout 2009
Summary of Procedure:
The Grignard reagent is added to a round bottom flask.
A mixture of benzophenone and ether is added to the Grignard over a peroid of 30 minutes.
The reaction is not heated.
The reaction is stopped by addition of aqueous sulfuric acid.
The triphenylmethanol is extracted with ether.
The product is recrystallized from hexane.
The product can be characterized by melting points, UV, IR, GC, etc...
Positive:
+We are learning this reaction in the lecture section. The acid work-up is especially instructive since this concept comes up a lot in reactions.
+Using a commercially available pre-made Grignard is a great idea.
+The reaction turns pink! Very nice.
+experience with an air & water sensitive reaction is important.
Neutral:
±Is a there a possibility of using an alternative to ethyl ether for the extracions?
±Triphenylmethanol has poor solubility in practically every solvent.
±Triphenylmethanol is difficult to remove from the round bottom.
±Determining if the two-phase aqueous work-up is a little tricky.
±TLC system should be optimized.
Negative:
-Grignard solution is unstable. Buy a fresh bottle for each lab period.
Inquiry & Extension Ideas:
●Versatile reaction: Many different carbonyl substrates can be envisaged. The JCE article suggests acetophenone and 4-chlorobenzophenone in addition to benzophenone.
●Further modification of the alcohol could be performed.
●Qualitative test to confirm the presence of a tertiary alcohol could be done for us low-tech types.
Chromatography & Spectra:
UV of triphenylmethanol in methanol 2008 (pdf)
Student Comments 2009
Photo Gallery:
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