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Failure trying to dry aq. methylamine in methanol
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Author Topic: Failure trying to dry aq. methylamine in methanol
sunlight
Member posted 07-07-99 02:24 AM
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It was suggested to convert aqueous methylamine in anhydrous methylamine in methanol using MgSO4.
FYI, I know that a experience using the corrects amounts of MgSO4, MeNH2 40 % and methanol, after filtering etc... yielded a 2 % methanolic solution of methylamine, with the lost of about 86 % of the loved monoamine.
It seems that the most part of the gas was in the water with the MgSO4, a good way to waste precious chemicals...
Rhodium
Administrator posted 07-07-99 05:49 AM
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Drip the 40% MeNH2 onto an excess of NaOH, and bubble the formed MeNH2 gas through the methanol instead.
sunlight
Member posted 07-08-99 03:44 AM
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Thanks Rhod, that will be my next dream. In the magnesium reduction they use KOH, it seems that a bee made it with success, do you think NaOH will work the same ?
Rhodium
Administrator posted 07-08-99 07:51 PM
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I don't know if the choice of base is critical in this application, but try a small batch with an equimolar amount of NaOH to see if it works.
MeNH2 note: Be sure to chill the methanol thoroughly when bubbling in the gas, the cooler, the more gas will dissolve.
Osmium
Member posted 07-09-99 10:40 AM
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Use excess base to push it out of solution. Choice of base really makes not much difference, but NaOH is cheaper and "more" otc.
To dry gases, KOH is better, because it doesn't liquefy as fast as NaOH (has higher drying capacity).
sunlight
Member posted 07-11-99 01:21 PM
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Thank you
Semtex Enigma
Member posted 07-11-99 03:33 PM
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So it sounds as though this could be used also for Ammonium Hydroxide, right???
Thanks as usual for any and all help...
Osmium
Member posted 07-12-99 07:38 AM
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Of course it can be done with NH3 solution, too, but why? Ammonium-containing fertilizer is much cheaper.
Semtex Enigma
Member posted 07-12-99 05:43 PM
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So how would one liberate the NH3 from the fertilizer? Perhaps by dripping conc NaOH solution onto it? Wouldn't the water absorb a load of NH3???
Osmium
Member posted 07-13-99 06:51 AM
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Not when you use strong NaOH. And even if it did, who cares? Fertilizer is cheap.
LaBTop
Member posted 07-13-99 10:48 PM
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Semtex, I told you as a side note that 1 L H2O absorbs 1000 L NH3 gas.
But when you drip CONC. NaOH or KOH solution on fertilizer, your not using 1 L H2O.
A LOT of NaOH or KOH can go into a bit of water.
There's your answer to your NH3 problem, you did not make a real saturated NaOH solution I think. LT/
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EMOTIONSwill always beFREE!
Semtex Enigma
Member posted 07-14-99 02:51 AM
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I think you've found the problem SiR LaBTop, SWIM thinks conc of the NaOH sol was around 35%, so that is probably it... Will have more notes soon, I hope...
Osmium
Member posted 07-14-99 03:56 AM
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Yes, water can absorb a lot of NH3, but a strong NaOH solution is something completely different. It will only absorb very little NH3, if any at all.
Semtex Enigma
Member posted 07-14-99 05:09 PM
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Thanks guys, you've been a great help as usual!!!
gyrogearloose
Member posted 08-02-99 10:12 AM
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Tried the Equalar molar amount of HCL in your 40% methylamine solution, (while damn cold)
then suck off the solution until its methylamine HCL, then try out the Naoh into the meoh with the HCL in it for the good way.......
LaBTop
Member posted 08-04-99 03:03 PM
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Yep, take a good practical advice like that, and you got everything back. He means with the last HCl: the MeNH2.HCl salt together with the NaOH solution(conc.) will form NaCl(shitloads!) and liberate the MeNH2 as the gas again which will readily dissolve in the MeOH(Methanol) and then its just decant the Methanolic MeNH2 off. Simple! LT/
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EMOTIONSwill always beFREE!
sunlight
Member posted 08-05-99 03:19 AM
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The last experience was to drip the aq. methylamine into NaOH. It's very curious because we expected some heat of the water when it was mixed with NaOH, but it seems that this exhotermic rxn is neutralized with the liberation of methylamine, obviosuly endotermic, so the temp keeps the same all the time, (chemistry is amazing) what means very little water can go with the gas. Other observation was that the methylamine is very soluble in methanol at 0 C (ice/water bath), no lost of product after bubbled the gas in methanol. In this first try we changed several times the equipment, and we finally got 75 % of the gas. I think next time it will be 85 % or so, what means 100 cc per 100 gr. of ketone, exactly like in Al/Hg amination, God is good.
LaBTop
Member posted 08-06-99 07:06 AM
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sunlight, busybee, this sounds as the ultimate solution for making MeOH/MeNH2 solutions for homecooks!
Please post a detailed write up(for newbees) in a new thread, so its easy to find.
And do'nt worry too much about water in the gas, because drying the MeOH/MeNH2 mix with dried MgSO4.7H2O(again,dry,so now without the water) proofed allready piss easy, just toss 10 to 20 % MgSO4 in, and mix a bit, and decant: Dry ! LT/
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EMOTIONSwill always beFREE!
LaBTop
Member posted 08-06-99 07:08 AM
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Apropos, strenght of your MeNH2.HCl/water solution? 40% ? LT/
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EMOTIONSwill always beFREE!
LaBTop
Member posted 08-06-99 07:16 AM
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Apropos II: what exactly do you mean with 100 cc per 100 gram of ketone?
Would'nt it be better to give weight/weight percentages? I mean start with 100 gram MeOH, what was the added weight for the MeNH2 gas? 10 gram? or much more? LT/
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EMOTIONSwill always beFREE!
prickleberry
Member posted 08-07-99 05:52 PM
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Why use MgSO4 ?? Prickleberry thinks CaO would be a much better drying agent to use for the MeAm/NaOH mix. This is because it's recommended for drying amines in good textbooks, so it won't react with the amine to reduce the yield.!! You should be able to add this directly to the MeAm.HCl/NaOH rxn. to help soak up the water and release your gas once reaction starts to slow down. It could also be used successfully in your drying column, although not as critical as in-tha-mix drying reagent. All hypothetical and untried ideas...but worth a go......Prickleberry.
sunlight
Member posted 08-11-99 08:19 AM
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LabTop, the 100 cc per 100 gram of ketone means that I used with AL/Hg that proportion, 100 cc of MaAm 40 % and 100 grams of ketone with good results. So extracting the gas from the aqueous solution by dripping it in NaOH (200 cc of methylamine over 350 grams of regular NaOH) gives a methanolic solution enough to play with 200 grams of ketone, something like 60 grams of methylamine in 600 cc of methanol.
I guess that no many bees have acces to aqueous methylamine , and they will work with homemade MeAmHCl, but probably the rxn will be very similar, the endothermic liberation of the gas will neutralize the exhotermic rxn NaOH+MeAm.HCl, if not heat is involved the amount of water in the methanol will be minimum and adding a bit of MgSO4 as you say would solve the problem. It might be tested.
ymir
Member posted 08-11-99 09:12 AM
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Loki's tips for making methylamine gas from the hydrochloride salt: A one gallon jug is loaded with the salt. A 1.2 molar excess of saturated NaOH is added slowly from a pressure equalizing dropping funnel, with swirling. After the addition is completed and when the reaction slows down, heat is applied to the jug with an oil bath, heated to about 120 degrees centrigrade. The gas is run through a reflux condenser, or the efficiency of a West/Liebig condenser can be increased using a coil of thin sheet metal inserted through the condenser. A drying tube completes the gas delivery system. The liquid that is to absorb the gas is cooled and stirred.
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