APO
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Trimethly Borate Without Sulfuric Acid and Triethyl Borane
I want to make trimethly borate but I will do anything to do it without sulfuric acid, I was thinking I could add equal molar mass amounts of boric
acid and methanol to a flask and reflux it and distill over the final product but I don't know if they will react without sufuric acid and the water
that is made decomposes the trimethyl borate before it distills over, maybe I could use a hydroxide as a descicant?
I also want to make triethyl borane so that I can add it to the trimethly borate to make a pyrophoric fuel with a hot burn tempature. I have no idea
how to use triethyl borane, maybe I could bubble diborane gas through some ethanol.
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UnintentionalChaos
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If you aren't able to get sulfuric acid, how in the hell are you set up to work under rigorously anhydrous conditions with inert gas for
triethylborane? This is probably best made by introducing a boron trihalide to a cold solution of ethylmagnesium bromide or ethyllithium. Adding
diborane to ethanol would certainly only result in a fire (since diborane is pyrophoric itself), if air is involved. No triethylborane would be
formed. You could, however, treat diborane with ethylene under the right conditions.
There is an excellently quotable bit about the dangers of triethylborane in "Excuse me sir, would you like to buy a kilo of isopropyl bromide?" and
I'll post it if I can find it.
[Edited on 2-6-13 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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APO
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I usually prepare anhydrous conditions using a vacuum chamber or desiccating chamber. Also I'm able to get sulfuric acid, I just don't want to use it.
To make an inert atmosphere I evacuate all of the air and fill it with a stream of helium continually or any inert gas, if I don't have any suitable
gases I usually burn a splint to remove the oxygen before adding the reactants .
Tell me more about diborane and ethylene, of course I would need to prepare the diborane under an inert atmosphere(or at least without oxygen
present), but what way am I supposed to add it to the ethylene? Do I bubble the diborane through the ethylene?
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Nicodem
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Thread Moved
6-2-2013 at 11:23 |
barley81
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Ethylene is a gas, so you cannot bubble diborane into it!
Triethylborane can be made by heating ethylene with 2% diborane in a sealed tube for four days. That does not sound very entertaining. If I had the
choice, I would choose the Grignard reagent route (not that I want to mess with triethylborane)
Reference:
http://books.google.com/books?id=9u9wrGqpvWoC&pg=PA44&am...
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APO
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Could I add proper amounts of ethylene and diborane to a test tube and liquify them by placing the test tube in dry ice?
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barley81
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Probably not, since the reaction requires heat according to that source.
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gauderbdf
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Hi everyone, this is my first post on the site and I apologize for my english.
Some days ago I tried to make ethyl borate without sulfuric acid and it work!!
This was just a preliminary test and have to be optimized, however this is what I did:
In a stainless steel pot I heated (by gas) around 66g of H3BO3. At first some water vapour was produced without any visible change in the pownder.
After some minutes the powder started to clump with continuos emission of water and, with the increasing of temperature, solids melted giving a clear
liquid boron oxide (similar to molten glass). Heating was stopped when almost all water was gone (but probably a little bit was still present) and the
system let to cool.
Solidified "glass" was broken by an hammer and collect.
To test, some pieces of B2O3 (I didn' weight it, but more or less 300-400 mg) was put in a test tube and heating with some ml of EtOH 100% (hardware
store quality) for two minutes until solids dissolved.
Burning this mixture the result is a green flame harder to estinguish respect the classical result with boric acid, sulfuric acid and ethanol, but a
little bit less green.
In the next days I'll try some variations, I'll post my results.
Bye
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Hexavalent
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I believe that this is just the ethanol burning, tinted by the boron compound you added...
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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woelen
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No, gauderbdf is right. This method indeed works. I myself made the methylester of boric acid in this way. Even simply adding H3BO3 to methanol makes
some of the methylester, but in that case the formation of water will drive the reaction more and more backwards towards methanol and boric acid, so
you get some equilibrium. With B2O3 you get the ester.
Making (fairly) pure trimethylborate can simply be done by adding MeOH to excess B2O3 and then distilling the ester. Making B2O3 is not that easy,
heating H3BO3 removes water, but some water remains and I believe that most people do not get further than HBO2. But with this HBO2 you also can make
the ester. Just add more of this stuff to the methanol.
I expect the reaction with ethanol to be similar to the reaction with methanol. Never tried myself, but I give it a good chance of success. Just try
it.
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DraconicAcid
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Rosesky and Mockel, in "Chemical Curiosities" claim that ethanol does not react as well as methanol to form the esters. If you are using borax as
your boron source, you have to add a great deal of sulphuric acid for ethanol, while a small amount will do for methanol. Making trimethylborate is
more likely to succeed without sulphuric acid than making triethylborate.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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kristofvagyok
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APO, you are a really funny kid...
You are afraid of sulfuric acid, but you would make BEt3? Do you know how that's like? It ignites on contact with air and burn as hot that can't
imagine. It is usually sold in 1M solutions in ornaic solvents (like THF) and it's under argon.
Quote: Originally posted by APO  | | Could I add proper amounts of ethylene and diborane to a test tube and liquify them by placing the test tube in dry ice? |
There are several more easy ways to lose a few fingers... It's aint tha complicated.
The diborane is also not a really funny thing, it also ignites on contact with air and it is fairly expensive. This is the main reason why they do NOT
make the BEt3 from diborane in labs. It is usually prepared from BCl3 or BBr3 and EtMgBr. The boron halides are really nasty things, better not to
work with them, but it's still million times better than the methods what you have described.
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
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