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Author: Subject: Sodium Borohydride
Famousroger
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[*] posted on 14-10-2014 at 13:52
Sodium Borohydride


Ok, so I've searched this site for a thread specifically on sodium borohydride, but have only found individual mentions in posts; if I am mistaken, and one already exists, my apologies on being redundant.

For what I can tell, there is no simple, one step method of using otc compounds and arriving at sodium borohydride being discussed online, from which most specialty borohydrides can be relatively easily formed (cyanoborohydride or triacetoxyborohydride par exam). I've seen several people suggest it as the only NOT OTC ingredient in a given synthesis, yet it is a watched chem in the United States, and I just simply can not accept that it can not be prepared "OTC".

So, without further ado, I propose the following based on logic and easily available Internet resources:

Step 1; prepare sodium hydride
Step 2; prepare trimethyl borate
Step 3; react products from one and two.

Step 1;
Prepare sodium metal from powdered magnesium, sodium hydroxide and a common firework fuse in a stainless steel, covered pot (a la http://m.youtube.com/watch?v=908rjHQ5mmc). Magnesium metal sourced from any available magnesium fire starters (for example http://m.acehardware.com//product/index.jsp?productId=128807... ). The magnesium can be made fine using a file.
The sodium product can be separated from the magnesium and paraffin (used to control reaction in referenced video) using melting point, sodium metal melts @ ~97 Celsius, parrafin melts starting at 37, and magnesium melts at 650 Celsius. I.e. any sodium and any other products should easily be separated using melting point...

Subsequently,
The sodium metal produced above would be hydrogenated to sodium hydride using hydrogen gas bubbled through molten sodium metal (if you need help generating hydrogen gas, use a search engine). This would ideally be done in an inert atmosphere, or hydrogen atmosphere i would conjecture; thankfully though, sodium metal does melt at low temperature. For all of this its maybe a good idea to construct an enclosure from plexiglass or similar to create a mild vacuum, nitrogen environment, etc. in inert environment bubbling hydrogen through the molten sodium will net sodium hydride, which melts/decomposes at 300*C, meaning this will be the solid product if temperature of sodium is kept ~100*C, making this relatively easy to isolate in descent purity. OBVIOUSLY, USING MUCH OF THESE COMPOUNDS IS DANGEROUS, AND EVOLUTION OF HYDROGEN GAS IS AN EXPLOSION RISK- MAKE SURE YOUR EQUIPMENT AND ENGINEERING ARE SOUND FOR ALL STEPS, ESPECIALLY WITH THESE COMPOUNDS-SAFETY CONTINGENCIES AND APROPOS PPE SHOULD BE USED. (MPs referenced from Wikipedia, also, Wikipedia does state this essential process as the prep method for sodium hydride)

Step 2;
Trimethyl borate can be prepared from the reaction of boric acid and methanol. First, we need boric acid; easy, addition of mineral acid to 'borax', I expect typical excess over molar equivalence. Clearly, few of us are using 100% HCl, nor is it nessecary for this. The boric acid has a relatively high MP, and BP around 300*C, so boiling off water shouldnt be an issue with this reaction; product should be produced virtually quantitatively. Boric acid dehydrates at 170 to meta boric acid (HBO2), and then 'pyro boric acid' at ~300 (H2B4O7). Any of these borates should accommodate the following reaction-heating to the meta borate may be wise, as heating to 170 assures no liquid water, nessecary for next step.
Once the boric acid is dried, reaction with methanol is performed in presence of H2SO4 with heating ( a lahttp://www.youtube.com/watch?v=ZNezFMq0NZU ). Trimethylborate has a BP around 68*C, so this will clearly vaporize in the conditions used to produce it, but should be relatively easily condensed, although some cooling to keep the product liquid will be nessecary in most indoor environments (ESP for storing)

Last step would be the reaction of these two products, really, producing the trimethylborate to be immediately reacted with sodium hydride seems ideal, from the reaction flask producing the trimethylborAte one could run hose into a second reaction flask with sodium hydride in an ice bath, effectively condensing the trimethylborate and agitating and promoting formation of the final product. After reaction with the trimethylborate, the sodium borohydride will be solid, with a MP of ~400*C, meaning excess sodiumtrimethylborate can be used, with any excess boiled off at room temperature from the product - an excess would garrauntee no remaining sodium hydride. The problem is; what solvent does one use for this final step? Diethyl ether? In addition, Wikipedia states this reaction is done industrially at 270*C, which is doable, but would require the trimethylborate be in gas state for the entire time it is in contAct with NaH, and it is hard to get good contact time between solids and gasses...regardless, this should work, and is doable with available materials. I suppose I can update on the stAtus and success of this endeavor if I attempt it, and if anyone is interested.


If someone has a better method, please share!

Thanks,
fRS
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[*] posted on 14-10-2014 at 14:43


Instead of reacting magnesium and sodium hydroxide, a Castner cell (see http://www.sciencemadness.org/talk/viewthread.php?tid=9797) is more feasible.

I don't see any obvious possible improvements to the other steps.

All in all, due to the labor and equipment costs involved, it's probably cheaper to buy sodium borohydride, even if you have to pay a lot for it.




As below, so above.
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Chemosynthesis
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[*] posted on 14-10-2014 at 14:48


Impressive research.
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[*] posted on 14-10-2014 at 16:04


Quote: Originally posted by Famousroger  
... bubbling hydrogen through the molten sodium will net sodium hydride, which melts/decomposes at 300*C, meaning this will be the solid product if temperature of sodium is kept ~100*C, making this relatively easy to isolate in descent purity.


Making methyl borate is straightforward enough:

http://www.sciencemadness.org/talk/viewthread.php?tid=16439

Sodium hydride, however, I suspect will be quite tricky. For example, see the synthesis in Leonid Lerner's book, Small Scale Synthesis of Laboratory Reagents..

After bubbling the H2 through molten sodium how do you separate the NaH from the molten Na. Filtration? Or is it dissolved in the sodium?

Once you have methyl borate and NaH I believe the synthesis would be straightforward per Schlesinger's procedure.




The single most important condition for a successful synthesis is good mixing - Nicodem
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[*] posted on 14-10-2014 at 16:08


I'm no expert, but aren't sodium metal and sodium hydride better reducing agents than the borohydride, meaning you could replace borohydride with the hydride or metal in many situations?
Or am I displaying my ignorance here?

One other thing I will say though is that separating the sodium metal from the magnesium oxide and unreacted sodium hydroxide and magnesium is almost certainly not as simple as you suggest. Nurdrage and many others have failed to find a way to do this easily, so I have doubts that melting under paraffin is all that's required.
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Dan Vizine
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[*] posted on 14-10-2014 at 19:17


Quote: Originally posted by Famousroger  


If someone has a better method, please share!

Thanks,
fRS


Much better.

http://www.ebay.com/itm/100g-Sodium-Borohydride-NaBH4-Good-P...
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[*] posted on 15-10-2014 at 00:40


Lol, glad to get some attention!

Ok, to start, despite my love for the snarky "just buy it" comment(s), I would feel quite inadequate to discover i am incapable of producing an essential, inorganic compound - one which I frankly took for granted in formal labratory settings - in addition, the nessecity to buy something leaves one vulnerable to its supply, a vulnerability i had always hoped to remedy via my study of chemistry; in other words, I do chemistry, why the f*** should I HAVE to BUY anything like that...I wanna be fucking martha stewart with molecules; put on an apron and go to iga, motherducker, "where making some sodium ducking borohydride"and, although I've already priced it out as cheaper - somewhat substantially so - to buy it, I would like to produce this compound as a practice in the art so to speak...in addition, its watched, and the last thing any of us need is some bullshit over sodium borohydride. It's essential. ->

And, this segues nicely to answer the question of WHY THIS REDUCING AGENT - well, sodium hydride, despite what you may immediately think, functions mostly as a "proton acceptor " (as a strong base) - although distinction from 'reduction' in this case may be somewhat unclear, reduction typically meaning reduction in oxidation state; this could be applied to the case of accepting a proton, subsequently reducing the oxidation state of the conjugate acid from which the conjugate base would be formed, H2, and yadda, yadda, but, in THIS application, a reducing agent is pretty specifically relative to ability to donate hydride anion...in fAct, per Dow chemical -(http://www.dow.com/assets/attachments/business/process_chemi...)
This MSDS describes uses of sodium hydride IN MINERAL OIL TO ANSWER THE SOLVENT PROBLEM. Applicable uses include reactions which require strong base not prone to reducing substrates or some such nonsense. Regardless, lets answer the question merely as "why sodium borohydride and not LAH or some similar, stronger reducing agent?" Answer is in the nature of intention - if i use a reducing agent strong enough to reduce, say, a ketone to a secondary alcohol, and my goal was to perform, say, a reaction on that same carbonyl of the aforementioned ketone, and produce, say, an imine, and subsequently reduce said imine to the amine to drive the equilibrium and produce appreciable amounts of imine formation/reduction; lots of times imines are in reversible equilibrium, reducing to the amine forces more imine to form based upon that equilibrium; if you aren't able to reduce to the amine, your yield of the imine product would be difficult to isolate, and yield was be terrible; this is why imines are so rarely isolated..or, if one wanted to selectively reduce aldehyde groups and not carboxylic acid moeities? It is very handy in carbonyl chemistry i guess one could say...

As for nurdrage video; I've not seen this, I plan to watch it immediately after this post,I think perhaps revising some aspects of approach, but isolation via MP should be adequate; I do not require high purity or yield at this step, nor do I expect it; I don't expect high sodium hydride yield or purity as well; given possible product and their properties versus desired product and subsequent properties, I am not particularly concerned, I suppose, with low purity or yield in production of sodium or sodium hydride. Your proposed contaminants are magnesium metal, magnesuim salts and sodium hydroxide? Not worried a about sodium hydroxide in less than 10% (admittedly, this figure is arbitrary), and magnesium has a much higher melting point; I can measure the magnesium based on the amount of remove able molten sodium; and Vici versi, also, I am building an enclosure for this and blah blah blah; in molten sodium the solid material should be separate-able :P. ugh, I should've just bought the shit...:(
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[*] posted on 15-10-2014 at 00:48


Again, though, oscillator does point out the potential failure of this, though, I should point that out. As I said, I am satisfied with functional product; magnesium can be isolated from products further down the line, IMO; what are proposed contaminations after NaH formation? I mean, frankly, if I can get NaH to form in molten sodium, that's what I am more concerned with, but, we shall see...I may fail at this, but, in another life i was an industrial chemist...in other words, a dirty chemist...omg, I am regretting committing to this by writing this...but, I just feel as though, until I find something train wrecking, I may as well try it, and, frankly, either ill post my train wreck, or reference to a train wreck awaiting collision(I.e. piece of information i am yet ignorant to)...again, I could very well fail at this, or discover something I can't do safely or confidently...again, I still have reading to do on this, and I appreciate the comments, I'm going to continue to look for failures, including watching the suggested viddies. Thanks, fRS
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[*] posted on 15-10-2014 at 02:14


I just wanted to say following your post that I was just providing constructive criticism to your prep. I can totally understand the impulse to make something rather than just buy it, and I honestly expect Dan Vizine would as well given his previous contributions to this forum.

As a further contribution though, it might just be possible to completely ignore your contaminations - just keep going until you have borohydride amongst a mess of MgO etc, then extract it with some solvent, avoiding more high temperatures and greatly simplifying workup. Wikipedia says the borohydride is stable at pH 14, so perhaps the leftover NaOH could even be used to your advantage.
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Dan Vizine
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[*] posted on 15-10-2014 at 07:06


Actually, Oscilllator, my stance is somewhat different than you might guess. When I set out to make a material, being trained in a synthetic laboratory that depended on completed products shipped, I don't try to reinvent the wheel. Especially for "simple" commodities like sodium borohydride, which isn't trivial to make unless you are in a well-equipped lab.

I try to emphasize keeping your eye on the prize, obtaining materials expeditiously with the least effort and cost. If it can be bought, buy it.

If you aren't doing anything suspect, the fact that NaBH4 is watched isn't a deterrent worth worrying about. So are Iodine and Lithium, but they are openly bought and sold by not only eBay users, but also by a number of companies.
Also, it is a certainty that this site is monitored. Announcing that you plan to make a watched substance will surely bring you as much attention as an eBay purchase will.

You may get a different perspective on the issue of making vs. buying as you get older. The path you aim to follow, Roger, may eat up a LOT of time. If you have time to burn, go for it.

And lastly, I've mentioned more than once that the main reason I am making my own ThO2 for my thorium project is only because I couldn't find a source to buy it. If I want to do more work, it would be on a new target, not on making every precursor. However, I realize that people here are not always motivated by my exact reasons. The joy of discovery may be your goal, and again, go for it if that's your stance.
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[*] posted on 16-10-2014 at 17:18


I apologize, I see you came to the same conclusion, although I posted before i read it. Yeah...you're right, that's what I was thinking. I appreciate the posts! I am currently working on a general enclosure, so, when that is completed i can begin this and tell you all how it goes. Right now I see sodium borohydride sold for roughly $50 for 100g, I so far have budgeted this as ;


2 x large(24 qt?)thick walled Tupperware style bins, translucent with latching top. ~$40
2 x forearm length chem resistant/heat resistant gloves(n - butyl would be ideal);15-$80
Aquarium glue silicon based glue; ~$25
1 x aquarium air pump; ~$25
1 x vacuum pump; ~$25
Stainless steel pot and lid; ~$15
4 x elastic band with hooks, 4'; ~$10
Small desk fan; ~$10
Ventilation tubing/PVC Pipe, 6'; ~$15
6 x rubber corks; ~$5
2x 12volt battery

Plus $40 for the borax, sodium hydroxide, magnesium, methanol and mineral acid.
That's $205 for a max yield of something like 1 kg, which is pie in the sky, if I yield 250g of reasonably pure sodium borohydride, I would be happy. This makes this endeavor an extreme investment for a small amount of sodium borohydride, and a lot of work, but most of it would be preparation, I need a reasonably good little enclosure to produce molten sodium and then subsequently sodium hydride. That little enclosure could become a serious danger if not managed properly. I will have a hose in for gas, hose in for vacuum. It will have a funnel loaded with sand gravity fed through a chute, which will be set to fall into the enclosure if anything runs away or goes awry (string pull trap/door). It will have 2 small holes for auxillary uses. It will have a sealable vent. It will be reinforced with 2x4s, and have a plywood external shield suspended via rope immediately behind workspace. Given the quantities i would manipulate at a given time, this is redundantly safe, and should greatly improve product via the use of largely inert atmosphere. Although, this isn't my only project, so give me time, will keep posted if anyone is curious...


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[*] posted on 23-10-2014 at 15:51


The Synthesis of NaH has been discussed here previously. Best information is probably in a thread on the synthesis of NaAlH4 and LiAlH4. Sauron posted a decent patent procedure at one point. As I recall, the feat can be accomplished fairly easily via the pressure hydrogenation of Sodium metal, in toluene, in a Parr type pressure reactor.

The reaction of NaH with Borosilicate Glass, appears promising as a means to produce NaBH4.

NaBH4 is fairly inexpensive.......industrially. But, you and I, generally cannot purchase it cheaply. Gotta buy a lot to get the friendly price.


[Edited on 23-10-2014 by zed]
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Dan Vizine
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[*] posted on 24-10-2014 at 09:34


$0.50/g IS pretty cheap.
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[*] posted on 24-10-2014 at 16:27


$500/Kilo

NaBH4 is handy for lots of things. I like to use it to generate hydrogen. It's very convenient to use, but pretty expensive....when used for that purpose.

Been a lot of work done recently, researching ways to regenerate Borate back into Borohydride.
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[*] posted on 25-10-2014 at 13:47


If you want to make hydrogen, aluminum plus aqueous NaOH is clearly a much better way to go, on a cost/L basis. Not quite as convenient though.

I still think 50 cents a gram is cheap, that's even less than the major players (like Aldrich) charge. I don't think many people who contribute here use NaBH4 by the kilo anyway, 100 grams will probably hold most of us for a while.

Your mileage, of course, may differ.

[Edited on 25-10-2014 by Dan Vizine]
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[*] posted on 14-9-2015 at 02:40


My very first post :D

I found this patent which claims to make sodium hydride by bubbling hydrogen gas through 5% to 50% sodium amalgam at 250C to 350C under reduced pressure. It then describes adding trimethyl borate to the amalgam and refluxing for 7.5 hours to yield sodium trimethoxyborohydride which might be converted to NaBH4 although I wouldn't know how. Unfortunately I can't find a whole lot of information on sodium trimethoxy borohydride but i would imagine given the fact that Sodium triacetoxyborohydride is a weaker reducing agent than NaBH4 that Na(MeO)3BH4 would also be a weaker reducing agent than NaBH4.

He used a soxhlet extraction to remove the sodium trimethoxyborohydride, which is an apparatus that i don't know much about but would like one for making absinthe. I'm not sure how you could go about removing the sodium hydride from the mercury other than filtration or the soxhlet apparatus. This entire procedure would also of coarse have to be done under an inert atmosphere. I actually really wanna do it because ive got couple hundred grams of cinnabar but i don't have a glove box.

http://www.google.com/patents/US2829950

https://en.wikipedia.org/wiki/Sodium_triacetoxyborohydride


[Edited on 14-9-2015 by Assured Fish]
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[*] posted on 14-9-2015 at 10:07


Alternatively you can replace methyl borate with boron trifluoride. Although dangerous as... well very dangerous it can be synthesised from fluorite, sulphuric acid and boron oxide. Pretty sure borax will also work, but more acid will be requirec and yield will be lower.
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[*] posted on 14-9-2015 at 15:08


Quote: Originally posted by MeshPL  
Alternatively you can replace methyl borate with boron trifluoride. Although dangerous as... well very dangerous it can be synthesised from fluorite, sulphuric acid and boron oxide. Pretty sure borax will also work, but more acid will be requirec and yield will be lower.


Boron trifluoride just sounds scary as hell with some nasty byproducts to, would it be possible to use boron trichloride or tribromide instead surely the prep for these would be similar.

And does anybody know anything about sodium trimethoxyborohydride?
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