The Grignard Reaction: Triphenylmethanol

The Grignard reagent, phenylmagnesium bromide is prepared in sodium-dried ether from bromobenzene and magnesium turnings in a flame dried apparatus. Ethyl Benzoate is reacted with the resulting solution, which after workup gives triphenylmethanol (triphenylcarbinol, trityl alcohol) in 45.0% yield, m.p. 158-160C (lit 160-163C). The procedure is a slightly scaled up version of the procedure given here: http://www.bc.edu/schools/cas/chemistry/undergrad/org/spring/Grignard.pdf. The intro music clip is from "Stealing Fat" by The Dust Brothers. I believe this falls under fair use.

Category:

Science & Technology

Tags:

• phenyl
• triphenylmethanol
• trityl
• triphenylcarbinol
• alcohol
• grignard
• reagent
• organometallic
• organic
• alkoxide
• tertiary
• chem
• chemistry
• metal
• metals
• magnesium
• Mg
• bromobenzene
• ether
• diethyl
• mechanism
• ochem
• ethyl
• benzoate
• compound
• chemical
• synthesis
• preparation
• phenylmagnesium

[AlChemicalLife]

if water is present dosnt it produce a hydrocarbon (benzene)?

[UC235]

@AlChemicalLife That depends. If there is water in the reaction mix before forming the grignard, the reaction that generates it will simply not start. I believe this is do to a skin of magnesium hydroxyhalide that forms on the metal. However, some grignards are much fussier about this than others. If water is added after the grignard formation, the hydrocarbon is indeed formed.

[HomesteadScientific]

Now, does Iodine catalyze the reaction with bromine somewhat in the way that bromine catalyzes some chlorine reactions?

[UC235]

@HomesteadScientific No, it merely serves to react with the Mg and disrupt the oxide layer (the MgI2 is soluble in ether) that otherwise coats the metal, enabling the bromobenzene to reach the metal's surface and react. a drop of bromine would work too, but is a tad too vigorous for my tastes...some bromine fumes poured in from a bottle would probably be fine as well.

[98JMA]

Great video, I was looking at the stopcock as you poured and thought to myself, 'Is he gonna close that?':)

I assume you could do this under argon instead of having the drying tube?

[UC235]

@98JMA Argon would be better. I would still flame dry the glass, just with a current of dry argon passing through the apparatus instead of dried air.

[yellowmetalcyborg]

Impressive!!

Most viewers don't seem to appreciate how difficult it is to perform a grignard reaction.

I thought that the sublimation of iodine in the midst of magnesium in the beginning was a little risky, but it all turned out very well. It's too bad youtube doesn't have an "applause" button.

[shibbyness]

Level 100 alchemy

[ihatefurrys]

Thank you sir. You just saved my butt in writing this lab report.

[stevenk113]

@AlChemicalLife Yes

[AlChemicalLife]

my mom is vary mean. i went to ask her what starting fluid was for and where it was sold and she started getting mad. all i was is asking a question.eney of u can tell me what it is used for ? and how much it is.

thanks

AlChemicalLife

[pomputin123]

Ironic, I am doing my chemistry homework´s.

[myst32YT]

Very Cool!!! Thanks for posting!!

[CarnalDiafragma]

I love this! I have done Grignard reactions before and never really known the mechanism. Those coupling byproducts always seemed so unlogical to me until you mentioned it being a radical reaction because of the SET.

Thank you very much!