womble
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propiophenone and stuff
NOTE: this was split off from the toluene -> benzaldehyde thread where it was completely out of place
Right. Following the train of thought (perhaps less well expressed by myself, than one would hope ) to proceed from benzoic acid + propionic acid =
propiophenone, I have tried to understand the synthesis from there.
I found this for the conversion of propiophenone to bromopropiophenone:
1)
To brominate the propiophenone, put propiophenone in glacial acetic acid
and drop equimolar parts bromine in the solution and shake (better
stirr) it. Now it must stand for half an hour. Hasn't the reaction taken
place (you can see it, if the sol. has the typical bromine-deep-red
colour) you can induce it by puting the beacer in warm water shortly.
Then the solution produces slowly, then more intensive, H-Br and the
colour disappears. Then drop it under good stirring in much cold water.
The bromoketone sinks as a colourless, heavy oil to bottom. To free it
from H-Br wash the seperated layer with water and NaCO3-solution. The
bromoketone cristallizes by 0 grade (Celsius). It should be
recristallized from ether.
(this is part of a rundown on the synthesis of M-Cat or ephedrone)
The bromoketone is then treated with methylamine to make methcathionone.
However, MC not being of anything more than marginal interest, is there anyway to hdyrogenate MCat back to ephedrine (or pseudo)?
I found this one a search of propiophenones (from rhodium)
Phenylpropanolamines from propylbenzene
http://www.erowid.org/archive/rhodium/chemistry/ppa.synthesi...
And this for the turning of propiophenones into phenylpropanones:
http://www.erowid.org/archive/rhodium/chemistry/propiopropen...
As the last suggests a procedure whereby hydrogenation can be used to turn the ketone into the carbonyl, could this take place after the bromination
and methylamine?
[Edited on 1-31-2007 by Polverone]
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kemm10
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This should work, if you want to reduce the ketone to the methylene group. It's from Chem. Commun. 514 (2003).
To a mixture of 1a [acetophenone] (5.00 g, 41.6 mmol) in 50 mL of water at room temperature was added Ni-Al alloy (25.0 g, Ni: 50%) in one portion.
The reaction mixture was stirred vigorously under reflux for 2 h. During the reaction, the pH of solution remained close to neutral. The mixture was
extracted with ether (10 mL X 3 times). The combined organic layers were washed with brine, dried over magnesium sulfate, and concentrated. The 2a
[ethylbenzene] was obtained in a 99.8% yield (4.41 g). The hydrocarbon products can also be isolated by simple steam distillation.
...Surprisingly, it was found that 1a was reduced to 2a in excellent yield, even at room temperature over a 24 h period...
[Edited on 1-2-2007 by kemm10]
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Organikum
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IIRC ephedrine was prepared by adding the methylamine and Al/Hg to the bromopropiophenone in the old days.
But for I guess you have something else in mind, you might have a closer look into the reduction abilities of hydriotic acid....
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zajcek01
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bromination?
I am sorry to revive an old thread on propiophenone, but I have a problem.
I would like to brominate propiophenone, but I don't have any acetic acid.
Is acetic acid really necessary for the reaction, or can another solvent be used
and some other acid added as a catalyst like a few drops of H2SO4?
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not_important
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It's not the acid so much as a solvent that doesn't react too quickly with the bromine or other brominating reagent. Alcohols can be oxidised, giving
an aldehyde or ketone which then gets brominated, for example. With elemental bromine CH2Cl2 might work.
In water - http://www.rsc.org/publishing/journals/GC/article.asp?doi=b7...
Another method uses anhydrous CuBr2 with ethyl acetate as the solvent, usually with refluxing.
Remember that alpha-bromo ketones are generally lachrymatory, and thus can be most entertaining to work with if your idea of fun is ripping your eyes
out.
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smuv
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I would dish out the 9 bux to get a liter of AcOH; it is the best solvent for the job. If you don't, remember to add a drop of acid to whatever
solvent you end up using.
@not_important: while this halogenation will go like a shot in virtually any solvent, AcOH can act like more than just a solvent in some halogenations
by transiently forming AcOX with a halogen (a good source of X+)
AcOH + X2 --> AcOX + HX
[Edited on 1-10-2009 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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stoichiometric_steve
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That is, actually, a VERY nice find! Thank you!
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Nicodem
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CH2Cl2 is also commonly used as solvent for alpha-bromination of ketones with Br2, however you need to add a pinch of AlCl3 as catalyst (1 mol% is
more than enough). Without a catalyst you risk a runaway since the bromination of ketones is autocatalytic (the HBr that forms catalyses the
reaction). Thus, without a catalyst the reaction can stay latent until you add already all the bromine and then runs out of control due to
autocatalysis (the bromination is exothermic!). Of course this is irrelevant for reactions on milimolar scale, but for larger scales you can risk big
troubles. Also, mind that in CH2Cl2 lots of nasty HBr gas evolves (toxic, corrosive fumes all around!) while in AcOH this is not a problem since it
remains in solution.
Don't forget the ice bath and check the literature examples first!
…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)
Read the The ScienceMadness Guidelines!
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zajcek01
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Thank you all for your replies.
I will try to use CH2Cl2 for the solvent and some AlCl3 as catalyst.
And as Nicodem suggested I will check some literature examples first.
The reaction will be in milimolar scale, so there should be little or no risk of runaway.
The nasty fumes will not be a problem for me.
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