Punk
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Bubbling ammonia gas into isopropanol
If one were to bubble dry ammonia gas into a chilled solution of anhydrous isopropanol could that solution be used for a birch reduction?
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chochu3
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The old literature describes the procedure for using isopropanol as a solvent for birch reduction.
\"Abiding in the midst of ignorance, thinking themselves wise and learned, fools go aimlessly hither and thither, like blind led by the blind.\" -
Katha Upanishad
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jimmyboy
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isopropylamine? hmm maybe - you will have to try it out and see - it doesnt sound too far fetched - yield's may be cruddy though - or a side reaction
may happen with your lithium/sodium if it isnt pure enough
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Punk
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Upon doing a google on it I find alot that call it isopropylamine salt.
This is a common chem used in pesticides and weed killers.
If it is a salt then maybe it could be isolated from an otc source, diluted in isopropanol and used in that manner avoiding having to create ammonia
gas???
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Punk
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WAIT A MINUTE
Jimmyboy im no chemist but I dont think bubbling ammonia gas into iso alcohol is going to create isopropylamine.
If that was the case methylamine would be a snap!
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jimmyboy
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you will have to chlorinate first of course..  - but i think you are looking for
something as easy as possible.. i dont think ammonia is very soluble in pure alcohol
[Edited on 13-9-2006 by jimmyboy]
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not_important
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You can run dissolving metal reduction in alcohols, although they tend to be so vigorous that the alcohol needs to be diluted with an inert solvent
(an ether for example). An alcohol's hydroxy hydrogen is some much more acidic than the hydrogens of ammonia that the metal will mostly react with
the alcohol; this may or may not give the reduction you seek.
Note that "isopropylamine salt" is refering to the salt of isopropylamine with some acidic compound. You need to pay attention to what that other
compound is, I suspect what you are seeing is glyphosate isopropylamine salt : http://www.ces.ncsu.edu/martin/glyphosate.html
As for isopropylamine, one route to it is to pass ammonia and isopropyl alcohol vapour over a heated cooper catalyst. This gives a mix if the mono,
di, and tri substituted amines; the relative amounts of each can be controlled to some extend by controlling the ratio of ammonia to isopropanol. The
amines can be separated by distillation, although the mixture may work OK.
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Punk
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well
Ive read about a safe " modified birch" useing methylamine hydrochloride and even ethylamine hydrochloride disolved in alcohol rather than anhydrous
ammonia.
Is there a reason why isopropylamine salt would not work?
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not_important
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Amine hydrochlorides are salts of simple inorganic acids. Under Birch conditions they react (mostly) with the metal amide or alkoxide formed by the
metal and solvent, giving the metal chloride and free solvent.
The "isopropylamine salt" is most likely the salt of the amine with glyphosate or Imazapyr, medium sized mutifunctional molecules. In the case of
glyphosate there are two P-OH groups that likely will react with the metal in preference to the solvent, plus the carboxylic acid function that forms
the amine salt, and glyphosate has its own amine function as well. Imazapyr contains a carboxylic acid, an amide, and an imide. Those functions are
likely to react under Birth conditions, reacting with the dissolving metal, possibly being reduced themselves, possibly taking part in other
reactions. They also will make product workup more difficult as you have organic amine-type gorp instead of something simple and inorganic like sodium
chloride as a side product.
Go look at the structures of the various "isopropylamine salt" compounds, study the properties of the components, and cognitate upon them for awhile.
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jimmyboy
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heck he wouldnt have to distill/purify the different isopropyl - amines would he? they would all dissolve the metal for the birch and work the same i
would think - since they are just going to be solvent
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Nicodem
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The prerequisite for any Birch type of reduction is that the solvent must solvate free electrons for enough time so that they can encounter the
substrate and do their reducing job. Ammonia does this perfectly. It can solvate free electrons (from the alkali metal solution) and these will
deprotonate NH3 only very slowly (as long as there are no traces of iron salts). Thus electrons in NH3 have all the time they need to reduce even the
ugliest substrates like aromatic systems.
Alkali metals can give their electrons to certain substrates even in solvents where they don't dissolve and where electrons don't have to hide from
acidic protons (like naphthalene reduction with Na in diethyl ether). But this is quite exceptional and also works only on exceptional substrates.
The life of a wandering electron in alcohols (pKa = 15-17) is very, very short, but some reductions with Na/alcohol still work fine.
The life of a wandering electron in the presence of acids like the proposed amine salts (pKa =8-10) is just about zero. To put it in layman's terms:
If your life would be roughly 0 seconds long, wouldn't it be quite unlikely to meet any nice substrate for matting, never minding the ugly ones?
What is the point of adding a weak acid to an alkali metal anyway? (besides the fun of watching the violent reaction, I mean)
…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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not_important
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| Quote: | Originally posted by jimmyboy
heck he wouldnt have to distill/purify the different isopropyl - amines would he? they would all dissolve the metal for the birch and work the same i
would think - since they are just going to be solvent |
If he's doing a true Birch on an aromatic, the mix would work; more or less what I said.
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Punk
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A simple yes or no with an explination of why would be nice.
My basic knowledge in chemistry is not enough to comprehend what you guys are talking about.
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jimmyboy
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short and skinny -- ammonia in isopropyl alcohol is a loser... isopropylamine salts - no good ... but if you want to make isopropylamine or even
ethylamine and dissolve your alkali metal in that .. that should work.. you will have to keep the oxygen out of your birch though -- use an inert gas
to blanket your reaction (liquid ammonia does this already so its just an extra step when you use a different amine)
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not_important
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And trying to use Roundup directly as the amine is a loser, too. The acid part of the salt makes workup difficult, as well as interfering with the
reaction. Then there are the other ingredients in the weedkiller, surfacants, co-agents, dilutants.
You could use weedkiller a a source of isopropylamine, concentrating the purchased material, adding a base, distilling off the amine (BP 33 C) and
capturing it in hydrochloric acid. If you want to do so, consider the MW of IPAM (~59) and glyphosate (~169) meaning very roughly 1/4 of the
"isopropyl salt" is the amine, and how much of the salt is in the purchased material.
edit - I'm tired and can't type.
Note that the modified Birch - amine and alcohol - may give different products than the orginal sodium in ammonia method; and different amines or
alcohols may change the product mix. It is also a bit sensitive to reaction conditions, more so then the ammonia method which was general run near the
boiling point of ammonia.
[Edited on 15-9-2006 by not_important]
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dr. nick
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err ... can someone put the practicle procedure of this secluding together?
Afoaf has a mass of 2-phenetylamine in stock and dosn't know what to to with it - i'm thinking of suggesting this to him.
Do you think this is of any value with 2-PEA used as the amine?
I don't want to risk to be embarrassed any more than absolutely neccessary ...
**edit: right after posting this it seems to me this might be a pretty daft idea ...
anyway, what do you think?**
[Edited on 15-9-2006 by dr. nick]
[Edited on 15-9-2006 by dr. nick]
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Punk
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| Quote: | You could use weedkiller a a source of isopropylamine, concentrating the purchased material, adding a base, distilling off the amine (BP 33 C) and
capturing it in hydrochloric acid. If you want to do so, consider the MW of IPAM (~59) and glyphosate (~169) meaning very roughly 1/4 of the
"isopropyl salt" is the amine, and how much of the salt is in the purchased material.
| Quote: |
What about dripping the amine directly into anhydrous alcohol?
I remember some good synths at the-hive of modified birch reactions used with ethyl and methylamine but I cant find them. |
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nightshade
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why not use acetone /ammonia then reduce that to isopropylamine.
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Panache
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Reading this thread is so frustrating i had to stick a compass in my arm and it hurt damm you!!! Oh the sweet agony of being misunderstood.
What about tributyl amine with salt and pepper? Has anyone tried that, could anyone comment? Would i just add my alcohol and ether mix to this with a
inert blanket to keep it warm. Would this give me my isopropylamineetheralcohol?
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