Protium
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Borohydride synth?
How can one go about producing Sodium Borohydride?
Can this be done relatively easily in a makeshift lab with basic glassware?
It just depends on how you look at it...
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JohnWW
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The first step would be to get diborane, B2H6. (BH3 is electron-deficient, which is made up for in the dimer by means of three-center bonding). This
is usually obtained by reacting elemental boron (or B2O3 may also be usable) with Mg, as mixed fine powders, in the absence of air (e.g. under argon)
to form Mg3B2, which is hydrolyzed by dilute acids to Mg++ and gaseous B2H6, which has to be kept away from air. (If B2O3 is used, more Mg is
required, and the product contains MgO which requires more acid to neutralize). The B2H6 is reacted with sodium hydride, NaH (from burning Na in H2
gas), in a suitable unreactive organic solvent, in the absence of air, to give NaBH4.
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mick
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You could try reacting lithium with and alkyl halide under dry conditions to form the alkyl lithium. React that in large excess with dry boric oxide,
under dry conditions, and you might end up with a lithium tetra boroalkyl reagent. Might be as good as sodium borohydride but not as good as lithium
aluminium hydride.
mick
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solo
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Here is a nice post with some patents for the synthesis of sodium borohydride.......solo
Attachment: NaBH4 patents.html (75kB)
This file has been downloaded 477 times
It\'s better to die on your feet, than live on your knees....Emiliano Zapata...\"Prefiero morir de pie que vivir siempre arrodillado.\"
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solo
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The Preprationof Sodium Borohydride by the High Temperature Reaction of Sodium Hydride with Borate Esters
H.I.Sxhlesinger, herbert C. brown and A.E. Finholt
JACS 1975,205
http://home.ripway.com/2004-11/211899/JACS_75_205-1.djvu
Note: if not able to download wait 24 hrs then download, they only allow me 10mb /day of downloads
It\'s better to die on your feet, than live on your knees....Emiliano Zapata...\"Prefiero morir de pie que vivir siempre arrodillado.\"
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HRH_Prince_Charles
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This paper from Rhodium reports no success with electrolytic reduction of borates to borohydride. The authors followed several of the patents with no
success.
Attachment: borohydride.electrosynth.pdf (105kB)
This file has been downloaded 445 times
Loather of monstrous carbuncles, lover of organic melons and servant girls.
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Marvin
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Worth mentioning the 'standard' prep for many years, does not use the rather toxic and difficult to make diborane, trimethyl borate is a
little on the toxic side but is almost trivial to make. Triethyl borate is much less toxic, only slightly harder to make and can also be used.
4 NaH + B(OCH3)3 => NaBH4 + 3NaOCH3
USP 2,461,661
USP 2,534,533
USP 2,683,721
It still leaves the problem of sodium hydride though.
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JohnWW
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What sort of environment, or solvent(s), are needed for that reaction?
BTW that home.ripway.com website is not operating.
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solo
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Ref: Needed route to borates
Procedures for Preparation of Methyl Borate
H.I.Schlesinger, Herbert C. Brown, Darwin L. Mayfield and James r. Gilbreath
JACS 1975, 213
Attachment: JACS_75_213-1.djvu (69kB)
This file has been downloaded 299 times
It\'s better to die on your feet, than live on your knees....Emiliano Zapata...\"Prefiero morir de pie que vivir siempre arrodillado.\"
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solo
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Ref: Sodium Borohydride Synthesis
The available synthesis of sodium borohydride....now for those that can't download from ripaway....solo
Attachment: JACS_75_205-1.djvu (137kB)
This file has been downloaded 342 times
It\'s better to die on your feet, than live on your knees....Emiliano Zapata...\"Prefiero morir de pie que vivir siempre arrodillado.\"
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BromicAcid
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Figured this was as good a place as any to post.
Today I attempted to make MgB2 from magnesium shavings and boric oxide. 11 grams of boric oxide (probably not toally the oxide, probably some boric
acid mixed in, dehydrated it a few days ago) and 15 grams of magnesium were jammed into a metal crucible in layers (as many of you know magnesium
shavings take up quite a bit of volume so this whole mix was fairly volumous). The mixture was put into an isolated system (i.e., a one way gas valve
was attached to the top) and after 45 minutes of heating with a propane torch, nothing. I removed it and found that the boric oxide with acid mixed
in had semi melted and turned it into a maleable mass. This might be a good method to make ignots of this to run this reaction, i.e., melt boric acid
and add enough magnesium shavings to it and stir.
Anyway, I had to heat the solid ball with a blow torch for about 3 mintues and then a bright light started that I continued to heat until it spread
through the mass, after allowing to cool I found that half of the mass didn't react, the bottom half. So I removed it and heated that. What I
ended up with was very similar to charcoal in color and how it felt when I crushed it. I ground it up noting a very few pieces of unreacted magnesium
but overall it looks like a good reaction. Must find if appreciable MgB2 was formed.
A note on magnesium boride, I've found a number of references to it as MgB2 (magnesium diboride) but I've also found a few as Mg3B2. Not
sure which is correct but since I found more references for the diboride I decided to shoot for that with my reaction:
B2O3 + 4Mg ---> 3MgO + MgB2
However what would the reaction for the magnesium boride reacting with HCl look like? I'm assuming its somewhat complicated being that diborane
will decompose in contact with water, but with Mg3B2 the reaction can at least be made to appear simple:
Mg3B2 + 6HCl ---> B2H6 + 3MgCl2
BTW, my intention is not to use diborane to produce the borohydride but directly in reductions, it is more powerful from what I've read, able to
reduce carboxylate groups whereas borohydride cannot.
There is no need to argue if an experiment can be made.
- H. St. C. Deville
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BromicAcid
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See the apparatus picture (attached) before reading the experimental section.
Today I decided I should test the potency of my magnesium boride. I took the product from my above reaction, 14 g and placed it into the bottom of
the vessel shown in the picture filled with smoke. The vessel had a sepretory funnel in the top filled with HCl to drive the reaction foreward, out
of the side of the two neck flask was a thermometer adaptor, the connection with the glass tubing teflon taped to prevent reaction. This glass tubing
lead to the inlet of a gas bubbler and they were connected with a pice of rubber tubing, teflon taped on both sides, the glasses of each touching
within. 100 ml of water was put into the gas bubbler and the vessel was evacutaed with a hand vacuum pump to decrease the explosion liklihood.
Upon adding HCl the flask immediately filled with smoke. (Fine B2O3 from reaction of diborane with the oxygen present?) The
smoke carried over a little and bubbled through the bubbler. Noticeable magnesium shavings (though low in quantity) were still in the mixture so gas
was expected from the reaction. I continued adding HCl as I have read that diborane hydrolyzes readily to boric oxide or acid in water (the intended
goal being diborane produced would hydrolyze in the gas bubbler and be precipitated with HCl then filtered and weighed). I added a total of 100 ml of
28% HCl to the mixture, and lots and lots of gas came over, it had a unique odor, like cured ham mixed with gym socks.
When it was all over no boric acid precipitate was present and the water smelled of that strange smell. I added some HCl to the water in the bubbler
hoping to precipitate some boric acid, nothing. Aside from the vessel filled with smoke the whole time and the strange smell nothing to show that
diborane may have been produced.
It may be a better plan to use the product from the thermite reaction directly and mix with aquous NaOH under reflux to yield NaBH4 such as in the
patents that are availible through the Hive material posted via Solo. Don't know about the solubility of NaBH4 but if it is fairly soluble then
filtration and crystalization is the key being that the other things should be fairly insoluble, the only real impurity then would be borates.
There is no need to argue if an experiment can be made.
- H. St. C. Deville
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12AX7
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That smell is odd to describe, isn't it?
I burned some B2O3 + Mg/Al a while ago, it's been soaking in HCl since. Still some clumps, suppose I should filter and pulverize it some
time...
Tim
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BromicAcid
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Off Topic and Rambling
No diborane can be detected by the reaction of magnesium boride and hydrochloric acid. After some investigation into the matter it was found that
diborane hydrolyzes so readily that it only has fleeting existence when attempts are made to produce it in this way. The reaction with magnesium
boride with HCl produces small amounts of hexaborane and others which were condensed by a number of chemists and fractionally distilled which yielded
diborane. The yields are very low <1% in many cases but can be increased to as much as 11% by using 85% phosphoric acid. The same can be said of the
reaction of sodium borohydride with hydrochloric acid which gives nearly quantitiative amounts of hydrogen, however with 85% phosphoric acid 40 - 50%
yields of diborane can be had, higher concentrations give better yields but foaming and such can be a problem.
Magnesium diboride was prepared in US patent 2942935 by the reaction of elemental magnesium with boron at 950 C under an argon atmosphere (According
to another paper if the temp is too high yields are reduced a thin iron or clay crucible should be used, nickel is attacked). The product was ~85%
diborane with the remainder magnesium. Upon heating this with potassium hydroxide solutions, the higher the concentration the better. An 8 M KOH
solution (250 ml) heated with 46 g MgB2 gave 12.4g potassium borohydride which was recovered by filtering, removing the water in vacuum, the
KBH4 being the first thing to precipitate out. The reaction can also be carried out in alcohols or even in the solid phase. The
following reaction is given in the patent for the formation of borohydrides assuming B2H6 is an intermediate product:
2B2H6 + 4MOH ---> 3MBH4 + MBO2 + 2H2O
In addition to treating potassium borohydride with phosphoric acid to give diborane, iodine, BF3 in ether, or mercurous chloride can
accomplish this reaction.
Although solutions of THF*BH3 are common, diborane is 10x more soluble in dimethyl sulfide and looses less reactivity over time in it.
The reaction of diborane with Na/K alloy gives a salt that can be sublimed at 400C which has incredible reducing powder. A test for boranes is to
bubble them though a solution of silver nitrate which causes a brown precipitate.
Sources:
Complete Treatise on Inorganic and Theoretical Chemistry pps 25-36
Recent Developments in the chemistry of Boron Hydrides H.I. Schlesinger ; Anton B. Burg 1941
Reduction of Organic Compounds with Diborane Clinton F. Lane Aldrich-Boranes, Inc. 1975
There is no need to argue if an experiment can be made.
- H. St. C. Deville
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no1uno
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Nugget of information, might help
The attached paper deals with the preparation of alkali metal borodeuterides from alkali metal alkoxides and trimethylamine.borodeuteride(d3).
Kinda nice, especially if we can access NaOEt from NaOH & EtOH. All we need now is a useful preparation of diborane that we can pass into the
trimethylamine (would triethylamine be as effective?)...
Attachment: syntheses.alkali.metal.borodeuterides.pdf (969kB)
This file has been downloaded 44 times
Here is about the best idea I can see: http://pubs.acs.org/doi/abs/10.1021/ja01097a050
What about reducing with aluminium? Yes, it is useless for the reduction of borate to boron, they are combined, but that warning that I see every time
I search for aluminium boride, suggests they give off borane(s) upon hydrolysis. Just a thought
[Edited on 2-4-2009 by no1uno]
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sparkgap
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Not too coincidentally, I was having yet another look at H.C. Brown's papers, so...
sparky (~_~)
Attachment: arcdibor.pdf (132kB)
This file has been downloaded 46 times
"What's UTFSE? I keep hearing about it but I can't be bothered to search for the answer..."
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no1uno
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Now, I'd have to wonder, is that pyridine borane which they purified by running the mixture of gasses through a dry-ice cold trap, comparable to the
triethylamine.borane that they used in the Canadian paper? Wonder if we could use pyridine.borane to produce the sodium/lithium borohydride(s) or
perhaps use trimethylamine/triethylamine to collect the relevant borane from the synthesis instead of pyridine?
Fuck, this looks tasty
PS BCl3 can be produced by the reaction of borates & PVC when they are burnt according to a study done by one of the fire brigade type journals. Yield
is shit, but hell Could one use aluminium diboride with dry HCl gas?
Attached is a file SOLO uploaded on another site.... Thanks & props are due to SOLO for it
PPS The separation of the mixtures, I wonder, could that be affected as H.C. Brown did it? Cold trap, then as the non-volatile triamine.borane?
Attachment: hydrides_of_boron._i._an_efficient_new_method_of_preparing_diborane-new_reactions_for_preparing_bromo-diborane_and_the_s (843kB)
This file has been downloaded 50 times
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