ORGLIST:A rookie question: Where did we go wrong?

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From: Teresa Atkinson (tla$##$eskimo.com)
Date: Tue Feb 17 2004 - 12:18:22 EST


I'm a second quarter organic chemistry student. One of our lab
experiments was to prepare triphenylmethanol from benzophenone and a
phenylmagnesium bromide grignard reagent. This is a traditional
grignard lab.

To do our lab:

We scrupulously dried our glassware.

We prepared the grignard from bromobenzene and magnesium shavings. The
reagent appeared to form as advertised.

We prepared our benzophenone/ether solution and added it to the
phenylmagnesium bromide grignard to theoretically make impure
triphenylmethanol. A very red solution formed (redder than other
students, although red was the proper color), then a pink powdery adduct
formed.

Lab was over for the day.

The next day, we added HCl to our solution to neutralize. Whereas other
students solutions turned yellowish, ours stayed red. I asked the
teacher why ours was red. He didn't know.

After extraction and crystalliztion, the crystallized substance was
still pink in color and the melting point was 151 degrees C. I haven't
yet had a chance to do an IR spectrum on the product, although I will.

Does anyone have ideas about why our product stayed red? Where did we
go wrong?

This lab is similar to the one we performed:
http://orgchem.colorado.edu/courses/3381manual/GrignardLM81S04.pdf

Thanks for any help. Any responses that I use in my lab report will be
cited.

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