andre178
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working with bromine
I am trying to prepare triphenyl methane using chromoform, chlorobenzane and magnesium by doing a Grignard. It's really messy, expensive and seems non
productive, is there a more clean way of doing it?
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rrkss
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You don't have an activated electrophillic carbon in that mix to run the grignard. Probably the easiest way I see for you to do this is run a
grignard with a benzoic acid ester and bromobenzene. That will give you triphenylmethanol. Then you can run a HI/Red phosphorous reduction to remove
the alcohol group giving you the desired product or use some other way to remove the alcohol group.
Remember to add an excess of bromobenzene as 2 equivalents will be added to the benzoic acid ester and some will be consumed attacking the alcohol
produced by the grignard attacking the carbonyl in the ester.
[Edited on 7-5-2010 by rrkss]
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UnintentionalChaos
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Quote: Originally posted by rrkss  |
Remember to add an excess of bromobenzene as 2 equivalents will be added to the benzoic acid ester and some will be consumed attacking the alcohol
produced by the grignard attacking the carbonyl in the ester.
[Edited on 7-5-2010 by rrkss] |
That's lost as a magnesium alkoxide, not an alcohol.
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1...
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'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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rrkss
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Yes you are right, I was thinking of the product produced after the workup to the intermediate.
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Nicodem
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| Quote: Originally posted by andre178 | | I am trying to prepare triphenyl methane using chromoform, chlorobenzane and magnesium by doing a Grignard. It's really messy, expensive and seems non
productive, is there a more clean way of doing it? |
I'm assuming "chromoform"=chloroform, "chlorobenzane"=chlorobenzene and that thus your preparation involves the reaction of phenylmagnesium chloride
with chloroform?
I found it bizarre that triphenylmethane would be formed this way in a preparatively useful way. Sure, it looks possible for the the dichlorocarbene,
formed from the reaction of PhMgCl with CHCl3, to react with another PhMgCl to form a carboanion which would reform a carbene by chloride elimination,
and this reacting further till triphenylmethyl carboanion. But chances that this would happen so smoothly for this being a preparative reaction were
in my opinion the domain of wild imagination. So I found it an interesting enough topic to search the literature about it, but could only find one
paper (Tetrahedron, 29 (1973) 349-352, attached) mentioning such a reaction gives a relatively fantastic 76% yield (the paper itself is
otherwise focused on the reaction of the so formed carbenes with cyclohexene). However it cites a book as the reference (by Kharasch and Reinmuth:
Grignard Reactions of Nonmetallic Substances) which I don't have access to to (and this book is most likely not the primary source anyway).
So I ask you to do now what you should have done in the first place already - to please share the reference as I would truly like to read more about
this type of reactions.
Attachment: 0349-0352.pdf (341kB)
This file has been downloaded 2384 times
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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andre178
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| Quote: Originally posted by Nicodem | | Quote: Originally posted by andre178 |
So I ask you to do now what you should have done in the first place already - to please share the reference as I would truly like to read more about
this type of reactions. |
Oh gosh, you mentioned earlier it was to up to the imagination, actually that's where that reaction came from. I am using the theoretical bookstuff I
learned in years of OCHEM. At this point I am like a toddler sticking cubes in the square shape cutoff, and cannot get the balls in the triangle
shaped one. |
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Eclectic
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http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0839
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