Author Topic: NaBH4 help needed  (Read 3588 times)

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XrLeap

  • Guest
NaBH4 help needed
« on: September 10, 2004, 12:44:00 PM »
Hi:) Good-day.

SWIM has read some posts, particularly interested in this

Post 439898

(LaBTop: "No. Wrong.", Newbee Forum)
it stated ethanol and DMF are having good solubility of NaBH4. Has any bee tried out using ethanol or DMF as solvent?

Can the methylamine gas be dissolved in these solvents easily? SWIM attempted many times IPA aka Barium's, yield was not as expected, SWIM thinks that he is not fated to use IPA and would like to switch to other solvent. Can any kind bee help to anwser this, thanks.


r2e3

  • Guest
see
« Reply #1 on: September 10, 2004, 04:47:00 PM »
rhodium's borohydride work up

it works. methanol is best.

if you can get the other solvents, MeOH should be the least of your worries

XrLeap

  • Guest
Hi r2e3, Thanks for the reply.
« Reply #2 on: September 11, 2004, 12:57:00 PM »
Hi r2e3,

Thanks for the reply.

SWIM reads in this thread,

Post 439864

(Vibrating_Lights: "Imine reduction", Newbee Forum)
Ethanol has got reasonable NaBH4 solubility, 4g/100g. At room temperature. SWIM also reads in some thread that ethanol can hold 33% wt of methylamine.

Does it call for a good solvent for NaBH4 reduction? SWIM thinks the only disadvantage is the price over Methanol. But it has the advantage of doing the reaction under Room Temperature, greater absorbtion of Methylamine freebase too.

SWIM faced some problems during gassing of methylamine into iced cold methanol. Keeping the methanol cold, preventing suckback, implosion, even made mistakes like flask filled accidentally with water from the ice bath..... :-[

from the thread:

Disadvantages of using methanol/water/polar aprotic solvents as solvent in sodium borohydride reduction:
Sodium borohydride reductions are usually conducted in methanol as solvent due to its high solubility in methanol.
Other popular solvents for reductions using sodium borohydride as reducing agent are water and polar aprotic solvents such as DMF etc.
 
Following disadvantages are encountered when these solvents are employed :
1. Reacts vigorously with lower aliphatic alcohol such as methanol and ethanol at room temperature liberating 4 moles of hydrogen.
2. Promotes side reactions such as ketals, acetals, hydrates, etc.
3. Protonolysis takes place in aqueous solution, rate increasing rapidly with increasing temperature and decreasing pH.
4. Organic molecules to be reduced are not soluble in water.
5. Sodium borohydride exhibits useful solubility in diglyme and DMF and could be used for the reduction but these solvents due to water miscibility and high boiling points make work-up of the reaction quite inconvenient, further ketones react very slowly in diglyme.

To overcome the above mentioned problems such reduction reactions are conducted in two phase system using non-polar aprotic solvents such as benzene, toluene, dichloromethane, diethyl ether and tetrahydrofuran (THF) using phase transfer catalyst.




It mentions DCM, DMF, toluene, ether are among the solvents that could be used in NaBH4 reduction.(with or without PTC). There so many possibilities.




LaBTop

  • Guest
Ahh, the memories!
« Reply #3 on: September 11, 2004, 04:34:00 PM »
That last link brings back good vibrations to me.
In that thread, there's so much hidden value, it still flabbergasts me that the combined potential of our members haven't jumped on the possibilities outlined all over the thread.
Especially the quaternary Boro ones, and the added PTC ones, I haven't noticed. Or did I miss it?
(Yes, I know of Bariums advice for use of Aliquat with his wet method)

Do we have a shitload of duplicated results a la Barium's wet method yet, or not?
I ask this, because you seemed not to have found them, and declare that you tried it multiple times with IPA as the solvent, with ?low? yields. LT/


XrLeap

  • Guest
Thanks for the reply
« Reply #4 on: September 16, 2004, 04:07:00 PM »
Thanks, Sir LabTop, for the reply.

SWIM had read through your boro in one pot thread, summed up to 109 posts. :-[  You sure have helped a lot of bees
' life easier. Allow me to say thank you, Sir.[bow]

SWIM's best result is about 40%(lowest was 0%) m/m using IPA(91% purity, 99% gave lower yield), SWIM believes it is due to his technique. Wether forming of amine was the cause or any other thing, SWIM always has a lot of mdp2pol as main product. If mdp2pol is good, SWIM has alreadly found out the way to have good yield. ::)

SWIM tried to remove water from IPA after generating of methylamine gas(methylamine.HCL solution mixed with NaOH solution, aka Barium's), by seperation. The stirring was allowed for 2 hours before seperation. Added NaBH4 solution(in water) to the IPA, and gave about 15% yield.

But one thing SWIM finds out, is the product(salt) is very good from IPA as solvent, there is no scienctific proof for this but was tested(blind test) with some other human objects.

SWIM is tyring to find out ethanol's possibility as solvent. As there is chem supplier selling it "Methylamine, 33% wt in absolute Ethanol". SWIM has read it somewhere about using ethanol, but no details described.

There is one post saying that Methanol is the solvent when using Methylamine, Ethanol is the choice when Ethylamine is used. Is this true?


LaBTop

  • Guest
Huh?
« Reply #5 on: September 18, 2004, 03:08:00 PM »
It's told by me ad infinitum, that waterfree Methanol is the premium choice to use in a one pot boro procedure. So I suppose you are talking about Bariums wet procedure. But why you are attempting to dry the IPA then, is unclear to me. PM Barium with a precise explanation what exactly you did, otherwise you won't get a response.

Endproducts, if recristalized 1 or 2 times, are all the same quality, doesn't matter which procedure is used, so your previous bioassays must have been from shitty, hurried cooks.

Trying to remove water from IPA by separation is just plain funny, that will never succeed.
Use mol sieves or oven-dried silicagel. LT/

EDIT: I see you already got help from a PM:

Post 531792

(XrLeap: "Easy NaBH4 amination", Newbee Forum)



XrLeap

  • Guest
Hi Sir LabTop, Thanks for the reply.
« Reply #6 on: September 18, 2004, 05:33:00 PM »
Hi Sir LabTop,

Thanks for the reply.

SWIM just typed a long post and accidentally pressed ctrl+w and closed the window.... :o

SWIM attempted The Archetypical "Good Guy", Bandil's method.

Post 503533

(Bandil: "Pseudo-"wet"- BH4 amination BH4", Methods Discourse)
It stated 80%+ of yield is achievable. However, SWIM used Barium's method to generate methylamine gas in situ, whereas Bandil used 40% aq methylamine solution. The IPA as solvent method is quite sentive to the parameters, and end yield will be affected badly. Side note, when water is very salty, it forms 2 layers with IPA. Most of the low yield was more or less due to SWIM's sloppy nature, that is also why SWIM is not generating methylamine gas to "pump" them into methanol.

SWIM is trying to explore the possibilities of using DMF and Ethanol as solvent. DMF is dipolar aprotic solvent, several things needed to find out/explore, solubility of NaBH4, solubility of methylamine.hcl, capacity of holding methylamine freebase. SWIM believe DMF fume is relatively safer than methanol's.

For ethanol, it is commercially available with methylamine dissolved. Easy preparation.

SWIM will report back his findings, but not too soon as he has only 1 day to work on his hobby in a week.


Sedrick

  • Guest
A guy I know from the Democratic of Congo...
« Reply #7 on: September 19, 2004, 08:23:00 PM »