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Topic: Synthesis of Triphenylmethanol -Grignard  (Read 13098 times)

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Offline gobuckskb9

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Synthesis of Triphenylmethanol -Grignard
« on: March 11, 2009, 06:05:55 PM »
I am working on my lab writeup for this lab. We made triphenylmethanol by reacting bromobenzene with solid magnesium and diethyl ether. Of course there was a workup step to complete the reaction (added HCl and water).

I am wondering what side reactions might have been competing with the desired reaction because I had a decent, but not great yield.

On that same note, I can't figure out what I would do to improve purity or yield of my product if I repeated this lab. I can't see anything in the procedure, and diethylether seems like a good reactant.

Any ideas?

Offline Dynamic

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #1 on: March 12, 2009, 12:15:36 AM »
Has anyone seen that bottle of benzophenone I left in the lab yesterday?

Offline aldoxime_amine

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #2 on: March 12, 2009, 11:36:30 AM »
Wow, what is that reaction? Are you sure triphenylmethanol ? All i can see is formatiion of benzene..



Has anyone seen that bottle of benzophenone I left in the lab yesterday?

What is the purpose of this post? ???

Offline macman104

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #3 on: March 12, 2009, 11:43:52 AM »
That's why Dynamic posted.  The reaction as stated currently doesn't make a lot of sense.  However, grignard of bromobenzene with benzophenone would give you triphenylmethanol.

Offline aldoxime_amine

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #4 on: March 12, 2009, 11:47:35 AM »
Oh!

Offline James Newby

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #5 on: March 12, 2009, 01:04:21 PM »
With making grignard reagents, getting all the magnesium to react is the tricky bit.  Everything needs to be as dry as possible and performed under nitrogen.

Did you do a TLC before the workup to see if all the starting material had gone?
4th year undergraduate at the University of Sheffield

Offline lutesium

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #6 on: March 13, 2009, 12:09:42 PM »
What are you using as the premier reactant? DiPhenyl Methanone? Yes formation of  Grignard Reactants is a little bit hard. Before starting flame dry your apparatus and be sure that your ether is fully dried by making him wait on sodium wire for a few days get a flame dried RBF put your flame dried stirring magnet and flush the RBF with Ar. Get your fully dried ether pour him directly from his place and then re-distill him with your flame dried apparatus by connecting your vacuum adapter and tube him through a CaCl2 tube. Before connecting flush your system with Ar by the place of the thermometer adapter. Connect your system through the CaCl2 tube run some Ar again. Distill off the ether. Now you have absolute ether. Before disconnecting the RBF containing the distillate have your Ar ready. Immediately after disconnection run some Ar over the flask and then cap the RBF strongly using a glass cap. If you don't follow these steps strictly you'll get Benzene.
What purification method do you use??? If distillation make sure that you use a vacuum distillation.

Hope this helps!!!


Lutesium...

Offline Dynamic

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Re: Synthesis of Triphenylmethanol -Grignard
« Reply #7 on: March 15, 2009, 10:08:07 AM »
Has anyone seen that bottle of benzophenone I left in the lab yesterday?

What is the purpose of this post? ???

Sorry, Al.  I was trying to stimulate his/her memory about the lab or stimulate the OP to better phrase the question.  Never a "DOH!" moment...

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