zbde00
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how to prepare diborane in situ?
The classic reaction is :
NaBH4+BF3.Et2O
I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too.
NaBH4+I2 or CH3I seems too expensive.
NaBH4+Me2SO4 .Me2SO4 is very toxic.
Is there any other easy way to prepare diborane?
[Edited on 25-6-2009 by zbde00]
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kilowatt
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If you are prepared to handle diborane, why would you be concerned about the toxicity or reactivity of any of the reagents used to prepare it?
Diborane is a pyrophoric (or nearly so) and highly toxic gas itself, and about as nasty as they get. Anyhow NaH and LiAlH4 can substitute for NaBH4
in similar synthesis routes, but they all involve boron trihalides and are similar in nature to those you listed.
The mind cannot decide the truth; it can only find the truth.
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Barium
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NaBH4 + I2 should not be expensive at all since iodine can be recycled in most cases. I prefer methanesulfonic acid and sodium borohydride. But I
don't understand what you mean by:
"I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too."
Liberated diborane can always ignite if you are sloppy, regardless by the method it is formed.
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zbde00
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Quote: Originally posted by Barium  | NaBH4 + I2 should not be expensive at all since iodine can be recycled in most cases. I prefer methanesulfonic acid and sodium borohydride. But I
don't understand what you mean by:
"I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too."
Liberated diborane can always ignite if you are sloppy, regardless by the method it is formed. |
In situ,diborane cann't ignite for it reacts very fast with other substance.
I have done NaBH4+H2SO4 system,it explode.
How about the yield of NaBH4+CH3SO3H.I know this method,but haven't done it.
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DJF90
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It most likely exploded due to atmospheric contact. Try the experiment after flushing the apparatus through with inert gas, and maintaining a steady
stream.
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ItalianXKem
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it' so dangerous ! B2H6 is higly flamable , low-med corrosive , toxic (so much for me , how other chemicals)
need a gas inert system
some info you can found on wiki
however need a reducing agent and a boron compound
eg. in pharmacy you find H3BO3 90-100% solid
good bye and good night (in Italy now is 0,26 AM)
The Italian X Chemistry is back !
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zbde00
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| Quote: Originally posted by ItalianXKem | it' so dangerous ! B2H6 is higly flamable , low-med corrosive , toxic (so much for me , how other chemicals)
need a gas inert system
some info you can found on wiki
however need a reducing agent and a boron compound
eg. in pharmacy you find H3BO3 90-100% solid
good bye and good night (in Italy now is 0,26 AM) |
H3BO3+ NaBH4 ?
It can work?
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stoichiometric_steve
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i've prepared BH3*THF by addition of BF3*Et2O or H2SO4/Et2O to NaBH4 suspension in THF. no explosion, no fire.
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Barium
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| Quote: Originally posted by zbde00 |
In situ,diborane cann't ignite for it reacts very fast with other substance.
I have done NaBH4+H2SO4 system,it explode.
How about the yield of NaBH4+CH3SO3H.I know this method,but haven't done it. |
When you made diborane from sulfuric acid and sodium borohydride, was it complexed with THF in situ, or was it liberated in gaseous form and dissolved
in another solvent?
It never ignites unless oxygen is present. So use a inert system and nothing will ever happen.
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stoichiometric_steve
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er, barium, read again?
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Barium
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Yes Steve, I've read it again. Now what?
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stoichiometric_steve
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what would the point be of adding an acid to a suspension of NaBH4 in THF if the BH3 wasn't going to be complexed to BH3*THF?
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Barium
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But Steve did you not see that my answer was directed to zbde00 and not you? He did not specify if his diborane preparation with sulfuric acid and
borohydride was performed in THF or not.
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stoichiometric_steve
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oh. pardon me, self-centered egomaniac 
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benzylchloride1
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Anhydrous aluminium chloride can be used to produce diborane and phosphoric acid can be used also for the same purpose. I would like to hydroborate
some alpha-pinene synthesizing the corresponding alcohol. I have sodium borohydride, boron trifluoride etherate and anhydrous aluminum chloride. All
the procedures I have been able to find use tetrahydrofuran as the solvent; this is unavailable to me at this time. Can diethyl ether be used for this
reaction?
[Edited on 4-7-2009 by benzylchloride1]
Amateur NMR spectroscopist
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stoichiometric_steve
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theoretically, diethyl ether is able to form a complex with BH3. although i have to say, one attempt i made was pretty much everything else than
successful.
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antibody
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Steve - was this done under an inert atmosphere? At what scale? Can you provide any details on your proceedure?
Thanks
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AndersHoveland
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| Quote: Originally posted by benzylchloride1 | Anhydrous aluminium chloride can be used to produce diborane and phosphoric acid can be used also for the same purpose. All the procedures I have been
able to find use tetrahydrofuran as the solvent; this is unavailable to me at this time. Can diethyl ether be used for this reaction?
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Despite the two similar compounds having nearly the same chemical reactivity, I remember reading something about diethyl ether not working, having
something to do with something precipitating or not precipitating out. I cannot find the information now, nor remember any of the details, but
remember the paper specifically saying that ethyl ether would not substitute for the THF, and thought to myself that this was very unexpected. But as
I cannot find the paper or remember any of the details, it may well be that the two solvents are completely interchangeable for the particular
reaction you are describing.
wikipedia also claims: "Lithium alumnium hydride is soluble in many etheral solutions. However, it may spontaneously decompose due to the presence of
catalytic impurities, though, it appears to be more stable in tetrahydrofuran (THF). Thus, THF is preferred over diethyl ether, despite the lower
solubility."
[Edited on 16-7-2011 by AndersHoveland]
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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jon
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the trick is to use iodine and nabh4
i'll bother myself with getting you the details.
| Quote: |
Due to this low reactivity towards esters, additives which enhance the activity of NaBH4
have been reported.7 For example, addition of iodine to NaBH4 in THF provides H3B–THF,
which is useful for hydroborations, reduction of esters and various others functional groups.8
Another example is the addition of zinc chloride in presence of tertiary amine that exhibits a
reducing property toward ester function.7
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http://www.arkat-usa.org/get-file/23589/
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Reaction of amides with NaBH4-I2 system in THF gives the corresponding amines in 70–76% yields. Reduction of nitriles yields the corresponding
amines in 70–75% yields. The I2/NaBH4 system is useful in the hydrocarboration of olefins and the corresponding alcohols are obtained in 78–92%
yields after H2O2/OH? oxidation. The reagent system is also useful for the reduction of carboxylic esters and acids to the corresponding alcohols in
60–90% yields.
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http://www.sciencedirect.com/science/article/pii/S0040402001...
[Edited on 17-7-2011 by jon]
[Edited on 17-7-2011 by jon]
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jon
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http://totallymechanistic.wordpress.com/2006/12/11/sodium-bo...
Give me librium or give me meth!
Patrick Henry....
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DJF90
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Anyone have a procedure for BMS starting from NaBH4? Thanks in advance.
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White Yeti
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Mixing magnesium boride and phosphoric acid would yield diborane, I think. But magnesium boride is difficult to obtain.
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jon
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there was this guy who made borane with magnesium boride it was pretty interesting, never boring let me see if i can find the transcript.
Give me librium or give me meth!
Patrick Henry....
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