Sciencemadness Discussion Board

10% methylamine solution

gunnz - 20-2-2006 at 18:39

The tooth fairy is having problems preparing this solution for a NaBH4 red. amination of mdp2p..whatever that means. She was dripping a con. aq. solution of NaOH onto MeNH2.HCl. The gas was directed into a flask containing -20C MeOH. After almost a hour of bubbling the flask was weighed and the total amount of methylamine absorbed by the fluid was minimal...under 1g. There was no detectable methylamine smell in the surrounding atmosphere and no leaks were detected. Her question is where has the gas gone and why was the uptake of MeNH2 in MeOH so minimal?

Her theory is that most of the gas was instantly absorbed by the water when the aq. NaOH solution was reacted with the salt and only a small amount of the gas was being pushed through the tube. By the ideal gas law 1 mole of the gas being a volume of 22.4L would only weigh 31g. She doesn't know if that much volume was bubbled in but it should be close. A gas diffusor was not used and the bubbles were quite big. Could that inhibit the gas from being absorbed?

Another option would be to collect the liquid MeNH2 using a dry ice/acetone condenser, however, that will be a last resort. Any legitimate input or experince would be much appreciated.

[Edited on 21-2-2006 by gunnz]

Boomer - 23-3-2006 at 04:21

Suddenly everybody is after methylamine, and I thought it was just me.

My guess would be the 10% soln had so much water it dissolved the freebase amine. Did you heat to drive it out?
I'd use a conc soln and solid NaOH, plus cool the MeOH in salt/ice. And a better bubbler!

How did you make the hydrochloride in the first place? Hexa/HCl or formaline/NH4Cl? Both drive me crazy, to the point of considering the acetamide route.

Edit: Sorry it was not you but the fairy. I don't need her since I am not going to use it for MDMA, but for an eutectic rocket propellant with ammonium/urea/hexamine (di)nitrate! ;)

[Edited on 23-3-2006 by Boomer]

temp. ?!?!?!

madchem - 25-3-2006 at 18:43

Your methanol is too cold (I believe this is you major prob)
Re try it with your methanol between 0-5degC
make sure your MeOH is dry and try and prevent moisture from getting in.
I would set it up similarly to an HCl gas generator
If you dont have a diffuser put a mag stirrer to get the bubbles to have the most contact with the soln (in reality, that is the purpose of a diffuser)

Thats all I can think of

Just my 2 cents

DeAdFX - 25-3-2006 at 20:48

Quote:
Originally posted by Boomer
Suddenly everybody is after methylamine, and I thought it was just me.

My guess would be the 10% soln had so much water it dissolved the freebase amine. Did you heat to drive it out?
I'd use a conc soln and solid NaOH, plus cool the MeOH in salt/ice. And a better bubbler!

How did you make the hydrochloride in the first place? Hexa/HCl or formaline/NH4Cl? Both drive me crazy, to the point of considering the acetamide route.

Edit: Sorry it was not you but the fairy. I don't need her since I am not going to use it for MDMA, but for an eutectic rocket propellant with ammonium/urea/hexamine (di)nitrate! ;)

[Edited on 23-3-2006 by Boomer]


Will that propellant even ignite? Some of my propellant formulations that use Ammonium Nitrate never ignited without the aid of magnesium powder:(

Boomer - 29-3-2006 at 04:04

The trick is to use an energetic fuel like HDN or MAN. It helps even more to add 25% RDX, in which case it stops being only a propellant and gets dual use (7000+ m/s)! :cool:

cool_arrow - 16-5-2006 at 10:13

- why not neutralize some of your gassed alcohol, evap, dry, weigh, and you'll know how much gas went into your cold alcohol (which is not too cold btw)?

bio2 - 17-5-2006 at 03:48

...She was dripping a con. aq. solution of NaOH onto MeNH2.HCl. The gas was directed into a flask containing -20C MeOH. After almost a hour of bubbling the flask was weighed and the total amount of methylamine absorbed by the fluid was minimal...under 1g........

Even with 50% NaOH this method sucks.
Yields under the best of circumstances
ain't good because as you suspected it's in the water if not the air. Methyl amine dissolves to 40% in water and the reaction
forms water so don;t use water!

Mix the 2 reagents in solid powdered or
fine granulated form using only a few drops of water to get it going and
please don't mix them all at once.

cool_arrow - 17-5-2006 at 09:52

>Mix the 2 reagents in solid powdered or
>fine granulated form using only a few drops of water to get it going and
>please don't mix them all at once.

Interesting. Question: If the reactants are mixed dry, and assuming a molar excess (say 2:1) of NaOH, what are the chances that a hard dry NaOH cake will form in the flask? Is the water evolved in the reaction enough to keep things in solution and reacting?

bio2 - 18-5-2006 at 03:49

.....f the reactants are mixed dry, and assuming a molar excess (say 2:1) of NaOH, what are the chances that a hard dry NaOH cake will form in the flask?.........

Pretty good I quess. Try it and let us know.

........ Is the water evolved in the reaction enough to keep things in solution and reacting?............

Well figure it out! 18ml water is 1mole, dissolves X NaOH
etc. etc.

Additional water can be added as needed. This is the same
method used to generate ammonia from fertilizer and
dry NaOH. If you use KOH then 10-15% more water is around.