pip
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otc sodium borohyride
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]
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chemrox
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sodium borohydride already is otc
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pip
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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?
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Siddy
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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?
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Nicodem
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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.
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Sedit
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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.
Knowledge is useless to useless people...
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fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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DJF90
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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...
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UnintentionalChaos
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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
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DJF90
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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.
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DJF90
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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.
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sonogashira
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| 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]
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UnintentionalChaos
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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?
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DJF90
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Yes he did say you just add a little more to compensate  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.
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madcease
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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
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madcease
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I found this msds for the Power packs.
http://www.poweritanywhere.com/pdf/MSDS_MS00005.pdf
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kclo4
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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.
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madcease
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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?
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zed
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As I recall, the NaBH4 or KBH4, synthesis is not terribly difficult.
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madcease
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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?
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