xaxax
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reduction of primary amides to amines with lithium aluminum hydride
I want to obtain a primary amine from oleamide with LAH. I have a problem with work-up. If i do work-up like that, is it OK?
First, i will place the LAH THF solution (2moles), then i will add the oleamide(1mole) dropwisely. After the reaction is completed, i will add water
to eliminate the excess LAH. Then,
should I use first NaOH or sulfuric acid?
I do not know how to exactly do work-up, because there are some information that makes confusion.
Help.
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mario840
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This is all wrong, first you must dry your THF with CaCL2, MgSO4 or etc. then sodium , dissolve hmmmm about 12- 17 g LAH in each 100 ml THF and then
dissolve oleamide with in THF , then add LAH solution to oleamide solution, next step is decompose remaind LAH , you take some methanol fort example
100 ml and 1-5 ml water and sowly add to LAH solution, the key point is to add wet solvent but not PURE WATER !!! after you add you can add carefully
drop by drop water and this is safe procedure. REMEMBER PAPER IS NOT THE SAME AS PRACTISE !!!! Be safe , but in my opinion it's waste of LAH 
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xaxax
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I want to ask how i can extract my oleylamine from the reaction mixture as i mentioned before.
after adding the aqueos methanol to the reaction mixture, what should i do for extracting and purifying the oleylamine?
Also, i want to learn something about oleamide that contains a double bond which can form an alcohol group by means of LAH. Is it possible to produce
an undesired alcohol when i make the reaction between oleamide and LAH?
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Nicodem
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Please UTFSE. The topic of post-LiAlH4 based reductions has been discussed several times already.
And don't listen to mario840 as he clearly does not know what he talks about, as his post above demonstrates. Check the literature instead or listen
to the people who had actual experience with these reductions.
PS: Please open referenceless threads only in the Beginnings section, where this one is being moved.
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Nicodem
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Thread Moved
24-7-2011 at 06:01 |
xaxax
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thanks Nicodem, i have some literature documents and they have different extraction and purification techniques. i am waiting you to give me an
advice.
i will use oleic acid and stearic acid with LAH.
after the reaction is completed,
1) adding water to eliminate the excess LAH.
adding dilute sulfuric acid
separating THF layer
extracting aqueous layer with THF and adding to THF layer
adding brine. drying with Na2SO4
evaporating THF
2) adding dilute sulfuric acid
separating THF layer
extracting aqueous layer with THF and adding to THF layer
washing with NaOH
adding brine. drying with Na2SO4 evaporating THF
3) adding water to eliminate the excess LAH.
adding dilute sulfuric acid
separating THF layer
extracting aqueous layer with THF and adding to THF layer
drying with Na2SO4
evaporating THF
fractional distillation
4) adding dilute HCI
adding K2CO3 and separating THF layer
extracting aqueous layer with THF and adding to THF layer
drying with K2CO3
evaporating THF
which step should be done? I don't want to make distillation after evaporation of THF.
:-(
Attachment: LAH -carboxylic acid.pdf (236kB)
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Attachment: reduction.pdf (211kB)
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vulture
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Do you have any hands-on organic chemistry experience? It doesn't sound like you do, because you can't extract an aqueous layer with THF as it mixes
with water. LiAlH4 is quite a dangerous reagent if handled improperly, it can cause severe hydrogen explosions.
Anyway, an easy purification of amines is to acidify, upon which the amine will go into the water layer as the salt, while any unreacted starting
product will stay in the organic phase. After separation, treatment with NaOH liberates the free amine.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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xaxax
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yes, i am very new and i am learning how to make reactions.
if i use diethyl ether instead of THF, can i extract amine from the water layer.
after i eliminate the excess LAH, i will add dilute sulfuric acid, then i will separate the ether layer and extract the aqueous layer. after washing
with NaOH, i will wash with distilled water. then, i will dry it with Na2SO4 and evaporate the ether.
after all of these, can i obtain pure amine?
[Edited on 24-7-2011 by xaxax]
[Edited on 24-7-2011 by xaxax]
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DJF90
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I suggest you scrap this projext for now and start with much less dangerous chemistry. Alternatively, you may look to the relatively safer reduction
using borane, which may be formed in situ. I doubt this can be used with your suggested substrate due to chemoselectivity issues, but you could always
select another readily available or easily made amide, as your objective here seems to be to learn practical chemistry. LAH isn't something to be
taken lightly.
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