03-07-04 02:10
No 493529
HI! Can one tell me an easy way to check the methylamine concentraction? I made methylamine-loaded alcohol, but i am unsure how much of the 99%+ nitromethane has been reduced to methylamine.
How can i get the methylamine out of it? I read the post from abacus - he is neutralizing the MeOH/Methylamin mix, then evaporate the alcohol+h2o. I did this, after the alholol was gone, boiling stopped immediatly and i was left with a orange/red coloured oil. Is this methylamine freebase? Is this a good way to check the concentration?
I read another post, where one gased the methylamine gas (from Al/Hg+nitro)into a NP, then evaporated alcohol and gased with HCl. Does this work. Is there a detailed writeup about this, or is this as easy as it sounds? Thanx in advance.
(Wonderful Personality)
03-07-04 12:14
No 493579
Methylamine freebase is a gas, so the reddish/orange residue in your flask cannot be the base and if you would have boiled away the base you would have smelled it for sure. And your neighborhood too. So you neutralized the methlamine which is basic with HCl I suppose and the residue is (impure) methylamine.HCl. Put it in the fridge and after a few hours the oil should crystallize. You may also extract this oil with boiling hor IPA and recrystallize from this whats easy as you dont have to boil away all IPA, just most and put the rest in the fridge then - methylamine.HCl is not so soluible in cold IPA so it will form wonderful crystals.
The amount if freebase in an alcoholic solution can be determined by titration, but how exactly is to be described by somebody with a better chemical education than I have. Vitus? GC_MS? Someone else please? PLEASE!
(Hive Bee)
03-07-04 16:20
No 493597
I know this is nothing new, but i never reach the expected yield after Al/Hg. Now i started to narrow the possible failures. The ketone is double distilled and has a slightly golden color. I am sure the error is located somewhere during my Al/Hg, i did a lot of them, but never reached the expected yield (just 2/3). Maybe i should try another alufoil, i just have this 0.15 'extrastrong' foil, i can not get another one. Maybe i should try the alupellets from my chemical distributor.
Since last week i make methylamine-loaded methanol. My intension was, if i know how much methylamine is in it, then i know the amount of ketone, which can be aminated.
I think 1 : 2.5-3 (ketone:methylamine) should work.
Thanx for your hint
(Stranger)
03-07-04 19:10
No 493618
I find it extremely weird that you don't get a solid upon evaporation of the volatiles after neutralization with HCl.
Assuming you get a solid product from the neutralization it's a piece of cake to calculate the concentration of the original MeNH2-solution.
(Wonderful Personality)
03-07-04 19:45
No 493621
He didnt evaporate but boil the methylalcohol away and so the residue in the (still hot) flask looks like being an oily substance also it is actually methylamine in sublimation.
I know the look.
Like oil.
The color.
And the feeling of: "WTF is this now?"
Its methylamine, it can actually used as is also recrystallisation from IPA makes it look much much nicer.
He should have stopped the boiling off of the methylalcohol earlier and put the residue in the fridge to get it crystallized from the alcohol - looks better. Next time he will do so but the methylamine isnt fucked up now, it still works.
(Hive Bee)
03-07-04 21:34
No 493634
Organikum, thanx again for your support. I will follow your advice and stop boiling a little bit earlier next time. I have read the posts about evaporating of methylamine freebase, the guys wrote that after a couple of days the oil was like before. And of course I checked only 100ml, i am sure my approximation for 1000ml should be ok. Thanx.
(Hive Bee)
03-08-04 01:43
No 493666
hi again. today i made 1l of methylamineloaded methanol,
i have used 80ml of nitromethane 99%+ purity. after that i filtered the whole thing through a buchner, hope this was nothing bad. I read that methylamine should be yellowish, is this true? I ask this, because the methanol is very yellowish now, hope i did it right. Thanx in advance for your help.
(Guardian)
03-08-04 11:56
No 493726
This titration will probably not be useful to you, however for those with aqueous solutions of methylamine; here is a titration that may help. I have never run this personally, however if I have time I will and report the results.
This is taken from the current USP:
USP27-NF22
Methylamine, 40 Percent in Water, CH 5N— 31.06 —
Assay — Using a syringe, transfer about 0.5 mL of a well-shaken specimen to 100 mL of water, at a point below the surface of the water. Determine the weight of the specimen by weighing the syringe before and after the transfer. Mix, and titrate with 0.5 N hydrochloric acid VS,determining the endpoint potentiometrically, using a silver-silver chloride pH electrode and a calomel reference electrode. Perform a blank determination, and make any necessary correction. Each mL of 0.5 N hydrochloric acid is equivalent to 15.53 mg of CH 5N: between 39.0% and 41.0% is found.
m_e
Unipolar Mania, It's good for life...
(Moderator)
03-12-04 04:50
No 494550
Both density and pH are also useful in determining the concentration of methylamine solutions, unfortunately such data is unavailable for methanol
These charts from the file available in Post 480133 (lugh: "Happy New Year", Newbee Forum) should bee helpful to many:
Chemistry is our Covalent Bond
(Wonderful Personality)
03-12-04 11:55
No 494593
I never seen the the methylamine article before - was a lil´ bit hidden I want to say - glad you linked to it again from here.
Helps a lot!
ORG