Sciencemadness Discussion Board

otc sodium borohyride

pip - 25-5-2009 at 19:33

so it seems best buy now has a full cell for ipods and the like called the medis 24/7 extreme portable charger. It is suposed to be powered by sodium borohydride and an alkaline alcohol solution. By reading this page: http://www.ohgizmo.com/2009/02/16/ohgizmo-review-medis-xtrem...
it seems that the borohydride is seperate from the alcohol until right before use when the user breaks an inside pouch kind of like an hot/ice pack.

As i have never handled it will someone who has the ability to test the purity take on the project?

[Edited on 26-5-2009 by pip]

[Edited on 26-5-2009 by pip]

chemrox - 25-5-2009 at 21:52

sodium borohydride already is otc

pip - 25-5-2009 at 22:04

as easy as the local electronics store or as easy as an account with a big chemical company? not trying to be rude but isn't it a little more difficult to get than calling aldrich and ordering or am I in the dark about it's ease of aquisition?

Siddy - 25-5-2009 at 23:28

chemrox, why dont you elaborate? There is not thing wrong with pip's post, it seems informative and interesting. And NaBH4 is definitely not OTC as pip said, you can not order from a chem supplier.

Im interested at least.

How would you test the purity, without Ion Chromatography or ICP-MS, and pure NaBH4 standards?

Nicodem - 25-5-2009 at 23:34

Quote: Originally posted by Siddy  

How would you test the purity, without Ion Chromatography or ICP-MS, and pure NaBH4 standards?

NaBH4 purity is tested volumetrically (by measuring the volume of hydrogen after hydrolysis). However, this will only tell you its purity and not confirm its identity or the identity of the impurities.

Sedit - 26-5-2009 at 07:57

NaBH4 is over the counter as Chemrox has stated and is sold as a solution with methanol IIRC for electroplaters for use in reducing heavy metals from the mother liquor. Hg and Pb salts get reduced down to there elements thru its use. I have never aquired it thru these means but I do know that it is sold in this form.

DJF90 - 26-5-2009 at 08:01

Sodium borohydride reacts with methanol though, IIRC to form a methoxyborohydride of sorts, which I believe is more reactive than borohydride itself. Or thats how I vaguely remember it...

UnintentionalChaos - 26-5-2009 at 08:17

Quote: Originally posted by DJF90  
Sodium borohydride reacts with methanol though, IIRC to form a methoxyborohydride of sorts, which I believe is more reactive than borohydride itself. Or thats how I vaguely remember it...


IIRC, it has KOH added to stabilize the borohydride in solution. The reaction products would otherwise be sodium methoxide and trimethyl borate along with hydrogen gas.

I think that you're thinking of the lithium trialkylborohydrides: http://en.wikipedia.org/wiki/Lithium_triethylborohydride

DJF90 - 26-5-2009 at 11:20

UC, that is perhaps what I am thinking of, although I was sure I had read something about NaBH4 and methanol leading to the same effect. Unfortunately I cannot remember where I read it. What I remember is that the researchers were using NaBH4 in ethanol (to reduce something I assume) and their product was different to what was expected; this was due to the methanol (partially?) reacting with the borohydride in solution.

And I thought that KOH is added to stabilise NaBH4 in aqeuous solution. In ethanol this may also be the case but I'm uncertain that the reaction with methanol can be prevented like this.

DJF90 - 31-5-2009 at 08:47

Sorry for the double post but it's been too long to edit

UC: I talked with my tutor today. He said that when LiAlH4 is used to reduce a ketone, the reaction is almost instantaneous, but with NaBH4, the reaction takes about 10-15 mins with warming. If a small quantity of methanol is added, then the reaction only takes 5-10 minutes, at RT. Methanol and sodium borohydride visibly react to produce hydrogen gas. The other product of the reaction is NaBH3OMe, and other alkoxy derivatives. The -I effect (inductively withdrawing) of the -OMe group is what increases the reactivity of the borohydride, hence the shorter reaction time. I just thought I would share this little jewel of knowledge with you.

sonogashira - 31-5-2009 at 14:09

Quote: Originally posted by DJF90  
The -I effect (inductively withdrawing) of the -OMe group is what increases the reactivity of the borohydride, hence the shorter reaction time. I just thought I would share this little jewel of knowledge with you.


I think you/your tutor have this confused(?)... or maybe mistyped? Electron donating ability of MeO- increases reactivity in borohydrides (B and O are very good friends :)) True electron withdrawing groups (CN, OAc etc.) are well known to reduce reactivity.:)

Edit: Oh, thank you to pip for sharing this information which is new to me!

[Edited on 31-5-2009 by sonogashira]

UnintentionalChaos - 31-5-2009 at 15:21

I don't really have any experience with NaBH4, but what is the stoichiometry like? Does only 1 of the 4 hydrogens react, or do several/all of them react? If the latter, you're losing molar equivalents of reducing agent for faster reaction times. This is of course, not an issue if you have a magical unending well of NaBH4 (such as in a research lab), but is a concern for amateur chemists for whom NaBH4 might be rather scarce.

Also, if the -OMe groups really increase reactivity that much, is it possible that you'd get unwanted side reactions by adding methanol?

DJF90 - 2-6-2009 at 07:17

Yes he did say you just add a little more to compensate :P obviously not something we can do as amatuers. I'm not sure about side reactions... I don't know how the reactivity changes given different substrates. Also I believe that more than one of the active hydrogens can be substituted for by OMe, but I really don't know to what extent.

sonogashira: Sorry this was a typo on my part! The -OMe group donates electrons to the boron centre (p(pi)-p(pi) interaction), making it more negative and hence increasing the activity as a hydride transfer reagent.

madcease - 2-6-2009 at 11:26

It would be interesting to know sometime soon how much of this Nab4 is inside these recharge kits. Never thought an ipod could have such good use till know lol

madcease - 14-6-2009 at 08:12

I found this msds for the Power packs.

http://www.poweritanywhere.com/pdf/MSDS_MS00005.pdf

kclo4 - 14-6-2009 at 22:56

Potassium tetrahydroborate 15-45%

Sodium tetrahydroborate 0-25%

Maximum liquid content is 70 ml.

That is from the MSDS above, according to the original link replacement cartridges are $25 each.

This sounds pretty expensive to me.

madcease - 15-6-2009 at 03:24

Yes very expensive if you ask me. Even for recharging your phone its not very bio degradable.
Cartridges can be purchased for a little under $20 if you do some shopping around.

Why does this type of fuel cell run it with 15-45% of potassium tetra instead of using the whole thing with sodium tetra

Anyone purchased and used one of these kits yet?

zed - 21-6-2009 at 13:45

As I recall, the NaBH4 or KBH4, synthesis is not terribly difficult.

madcease - 25-6-2009 at 05:49

Im sure the NaBH4 synth isnt difficult depending which one you are reffering to
But im sure its alot less time consuming to just get a power pack

Can reductions still be done in same yields and treated same weither NaBH4 or KBH4?