Author Topic: NaBH4 is just amazing.  (Read 29677 times)

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  • Guest
Thanks mate
« Reply #20 on: March 27, 2004, 09:45:00 PM »
thanks buddy for the reply:)

however, there are some more questions following them, swim is puzzling and doing a lot of reading. swim just can't visualise how to make them happen.....

1)can swim just prepare some methylamine.hcl and add them in sodium hydroxide in a rbf(thus producing methylamine gas)?

2)and the product needed would only bee the gas to dissolve in the rxn vessel(the methanol mixture from NaBH4 reduction method for e)? the other by-products are all not needed, but can swim just add NaOH and methylamine.hcl in the methanol mixture in the rxn vessel?

3)can swim just place the rbf(2 neck) higher that the rxn vessel to pull out the methylamine gas by the differential pressure, as methylamine always drop onto floor?

sorry if these questions sound stoopid.... :-[


  • Guest
arghhh... i really do sound stupid.
« Reply #21 on: March 27, 2004, 09:55:00 PM »
arghhh... i really do sound stupid. the answers to my questions are all here....

Post 443313

(LaBTop: "Hydrous Boro One Pot !  AT LAST!", Methods Discourse)


  • Guest
RE: What's so difficult about the Al/Hg reaction?
« Reply #22 on: March 27, 2004, 11:51:00 PM »
Baalchemist: Probably you're right. Perhaps I'm a bit overscared and a sissy, but I strongly disklike working with compounds like HgCl2 in amounts required for medium-scale RXNs. If anything runs out of control (and everyone experiences this now and then), you will have a problem if the rxn didn't take place in a lab fume hood  :o  ;D . And therefore it's not a question of yield but rather security/health issues...  :)  (although borohydride is toxic, too, but mercury-2-chloride is quite a bit more nasty I thought.. Did you know that mercury poisoning causes insanity?)

I absolutely don't doubt that Aluminum Amalgam reductions can produce very high yields at low cost of reagents and short rxn times. But I thought that avoiding the use of toxic compounds (where possible) is good lab practice? :-[  (ok perhaps I'm just too scared, but I just cannot feel safe when I know that there MIGHT be some residual mercury-(whatever) traces at my work space beecause a recent Al/Hg reduction was a bit too exothermic/not enuff ice was at hand :( , lack of experience indeed. Of course this is only fictional and didn't happen at any time.  >:(  >:( )
But It's of course the method of choice for big scaleups!  8)

DeeMtermined: WOW! Looks indeed very beutiful, really sparkling! (hats off)

XrLeap: Nice thread you digged up! Thanx for the info! Will have to do some reading..  ;)


  • Guest
Hydrous Boro One Pot ! AT LAST!
« Reply #23 on: March 29, 2004, 02:23:00 AM »
Hi! I am very interessted in this method. My question is, has one more detailled infos for aminating MDP2P with NaBH4 using this method? It says "Longer reaction times and 4-5 eq ethylamine should give better yields". So, how long should i run it, and how much methylamine.hcl should i use ? Greetings


  • Guest
When using the "wet" amination ...
« Reply #24 on: March 29, 2004, 01:27:00 PM »
When using the "wet" amination scheme, the best yields are usually obtained from using a 1:2.5 ketone to methylamine ratio. Mix the ketone and aq. methylamine in a proper solvent (IPA is fine), cover the mouth of the flask with some foil and stirr it for about one hour at rt.

After one hour you can add the aquous borohydride solution(1:1 ketone:NaBH4 molar ratio is perfect ) dropwise while stirring heavily. Please remember to basify the aquous medium you are using for the borohydride prior to the introduction of the hydride, to avoid decomposition. After addition of the borohydride, the flask is covered with some foil and stirred overnight (a few hours is usually enough, but better safe than sorry).

Then proceed with workup as usuall. Quite an amount of xP2Pol can be salvaged from the non-polar washings, so please do reuse this for other runs. Rhodium has written some good posts on this topic.



  • Guest
« Reply #25 on: March 29, 2004, 07:44:00 PM »
thanx for your advice, will try it this weekend.


  • Guest
Armageddon; Those fears are just normal, and...
« Reply #26 on: March 30, 2004, 11:04:00 AM »
Armageddon; Those fears are just normal, and may subside in time. The reaction needs headroom mainly in order to 'keep it together' safely. The Hg salts are used in minimal amounts(200-300mg's will work in a 100-150g reaction) Big, oversized flasks will give the best returns. Baal had used his 22L for 100g reactions, and with the large amount of available headroom, it could be run at full bore without a worry & return 100g+ in a final yield. Ultimately one needs a comfort level with any reaction method they choose. Regardless, its great to hear about success for anybody using any available method.


  • Guest
Armageddon: If (Al/Hg) runs out of control...
« Reply #27 on: April 01, 2004, 01:14:00 AM »
Armageddon: If (Al/Hg) runs out of control... you will have a problem if the rxn didn't take place in a lab fume hood

First, the "Hot Part" of the Al/Hg only lasts about an hour at most.  If you cannot stay put and watch your reaction for that long, don't do it and find another hobby.

Second, if you do get a runaway reaction, holding chunks of ice to the sides of the rection flask will slow it down enough to avoid an erruption.

I know that there MIGHT be some residual mercury

The elemental mercury will be in the sludge as a small drop.    If you want to be certain of mercury free product, you will have to distill your freebase (after washes, of course).

Baal: Baal had used his 22L for 100g reactions

Are you talking about a nitromethane Al/Hg, or are you missing a 0 there?  A carefully controlled 100g nitromethane Al/Hg can be run in a 5L flask.  A 250g MeAm Al/Hg can be safely run in a 5L flask.  You must really demand a lot of headroom.


  • Guest
If you want to be certain of mercury free...
« Reply #28 on: April 01, 2004, 01:28:00 AM »
If you want to be certain of mercury free product, you will have to distill your freebase (after washes, of course).

And If you want to use the patented double-condom-safety(tm), you could make the alpha-lipoate salt with alpha-lipoic acid.. It removes quite efficiently Hg and other heavy metals from your body.


  • Guest
Seriously, don't try that.
« Reply #29 on: April 01, 2004, 02:32:00 AM »
I do not think alpha-lipoic acid will give a suitable salt.


  • Guest
swim is noobee and swim do not like to assume...
« Reply #30 on: July 04, 2004, 12:28:00 AM »
swim is noobee and swim do not like to assume things he does not understand, so, asking a question that might sound stoopid.

can one use methylamine.hcl and add them to the solvent(methanol in this case), will the yield be affected badly, or will there will any yield at all?
in the earlier post stated methylamine, swim is assuming methylamine gas, right, there is methlymine solution so which is the actual used chemical?
in the rhodium site, methylamine.hcl was mentioned could be used, but so far no %yield was reported. can any bee kind enough to share the experience?



  • Guest
glassware setup
« Reply #31 on: July 14, 2004, 11:54:00 PM »
What type of glassware do you use for dissolving your methylamine gas into the methanol and how is it set up?  Assume that your reacting methylamine.hcl with NaOH.  I've read the huge scale method using a gas tank and a tank of methylamine(by Labtop?) but I'm asking about smaller quantities with regular glassware.


  • Guest
It was like pressure equalized addition funnel
« Reply #32 on: July 15, 2004, 05:06:00 PM »
It was like pressure equalized addition funnel on 2 necked RB with other neck connected to tube which lead to chilled methanol.Saturated NaOH solution was dripped into MeAm.HCl and that was about it.Learn to control the apparatus,suckbacks occour if you're not careful(add NaOH solution slowly and don't cut the flow suddenly and stir the mixture constantly).You may want to use wash bottle between apparatus and methanol solution.


  • Guest
i cant wait
« Reply #33 on: July 15, 2004, 10:40:00 PM »
i have the cleanest me.hcl and FB - a yield would be good - have such a complicated rig to get rid of water now - free partie this w/e too - be nice to be cuming in my head - tired of all the street shite....... been too long


  • Guest
another question for cub
« Reply #34 on: July 20, 2004, 12:07:00 AM »
Ok cub, so the tube that carried the gas to the methanol came up through the bottom? or came down through a stopper of a flask with the tube going down to the bottom of the flask or what?  Was there a vent in the flask with the methanol for any built up pressure or does the methylamine get absorbed completely with no increase in pressure?  These may be stupid questions but I'm not familiar with dissolving gas into a solvent.


  • Guest
Here it is,cub also advises to use flask for...
« Reply #35 on: July 20, 2004, 07:56:00 AM »
Here it is,cub also advises to use flask for methanol and not a beaker,in a beaker it'll fly into atmosphere faster than you can add it.In a flask there will be very small loss and smell.


  • Guest
Wet piece of fabric to trap smell
« Reply #36 on: July 20, 2004, 10:49:00 PM »
Nice drawing Cub! To prevent methyl amine gas escaping you could wrap a wet piece of fabric around the top of the left flask (Even better, use a second wash bottle filled with methanol)


  • Guest
and dont forget!
« Reply #37 on: July 21, 2004, 12:18:00 AM »
to have a diffuser to break the gas into nice small bubbles with continuous cooling -ie 4C i have seen - when cool enough - the gas will literally disappear into solution - ie no smell.
the tube in the diagram should have a few holes (25 gauge) -not to many tho and the bottom plugged to enhance the dispersing effect.


  • Guest
What about cooling???
« Reply #38 on: July 21, 2004, 03:56:00 AM »
Cublium, do you cool in some way, the tube leading to the methanol?
Or do you use cold methanol in a cold bath, along with cold naoh and meam solution??

Ive never gassed meam but i was under the impression that cold methanol(ex -20 celcius) wouldnt be enough to keep the meam in. I taught that you would need to cool in between the meam and methanol.

Do you know how much dissolves in for how much initially used???
Could the proper setup be that simple??? I have NaBh4 lying around, i feel like trying a reductive amination of that sort on a primary amine and ketone


  • Guest
Cublium, do you cool in some way, the tube...
« Reply #39 on: July 21, 2004, 10:57:00 AM »
Cublium, do you cool in some way, the tube leading to the methanol?
Or do you use cold methanol in a cold bath, along with cold naoh and meam solution??

Methanol is first prechilled in freezer to -20 C.Then it's gassed some time and temp rises as methylamine dissolves(solvation seems to be exothermic or methylamine itself is hot as it comes from the generator).When temp rises to few degrees C,stop addition,put stopcock on methanol flask and return it to freezer,and so on till right amount has been added(weigh with scale but use a quality scale or it won't show anything useful when liquids are measured,but good scale will show exactly how much has been added).Cub used a small generator consisting of 2 liter flask for methylamine,half liter press eq. addition funnel and 2 liter flask for methylamine and gassed in few hours over 300 grams of gas to 4 liters of methanol to do a 1 kg PMK reaction.He got nearly 900 grams of amine salt out of that one ;D .He gassed 1 liter of methanol at the time and frozed it few times as it got warm during solvation.When 1 liter was gassed,poured it to 10 liter flask which was kept in freezer and proceeded to gas another liter and when all 4 litres were gassed and cooled to -10 or so,ketone was added in 1 portion,no warming was noted and temp stayed same,solution turned to dark orange though.Then started adding borohydride and so on.Total success even though it was cub's just third NaBH4 reduction(former two were good too,over 85% w/w from both).It's very easy reaction,hard to fuck up if you have already some experience on that matter.Let me put it that way:if you succeed in making ketone from safrole,you definitely succeed with NaBH4 reduction in any scale,it's really as easy as i tell it is,i'm sure many bees can confirm that.