methylamine syn needed

Badger · Sat Feb 19, 2005 5:14 am

I would appreciate a post on synthesis of methylamine. I found Rohdium's very difficult to follow as he goes on and on about his teflon frying pans and kitchen crap.

IndoleAmine · Dreamreader Deluxe

In a 2000ml RBF with distillation setup, place one mol hexamine, four mol of hydrochloric acid and 3 mol absolute ethanol. Slowly heat on a waterbath until ethylformate starts to distill over at max. 53°C. The heating should be doen *slowly*, like over the course of 3-4 hours.
When all ethylformate has distilled, turn the heat up to 108°C bath temp. and continue distillation until all remaining EtOH and water are distilled as far as possible without applying more than 108°C heat to the rxn.
When nothing distills over anymore, cool to room temp. in cold water bath. Ammonium chloride will precipitate and has to be filtered off. The filter cake is washed with a little EtOH and the whole thing is again distilled with 108°C bath and the help of a moderate vacuum until the volume of the remainder is only 1/2 of original volume.
Cool to rt again, filter off unreacted NH4Cl again. Wash 2x with hot EtOH this time, and distill filtrate and washings together until it starts to crystallize (you can do it with more temp. this time, like 140°C bath themp.) and no water can be removed anymore through any distillation.
Cool to room temp. and collect the precipitated methylamine.HCl by filtering off with suction. Concentrate the filtrate to 1/2 of its volume and cool again to obtain a 2nd crop of methylamine.HCl. Repeat if you feel like you have to.

Now we will purify the methylamine (free it from byproduct dimethylamine and unreacted ammoniumchloride that crystallized too):
For this, we dissolve the methylamine.HCl in anhydrous(!) isopropyl alcohol by refluxing it 10 minutes with 350ml abs.iPrOH (drying tube on top of condenser!), letting settle and pouring the IPA saturated with MeAm.HCl into a beaker. This is placed in the fridge to precipitate the methylamine.HCl as clean, nice crystalline hexagonal plates. This is filtered and the alcohol used for another extraction of the crude product. This whole thing (refluxing/decanting/cooling/filtering) is repeated 4-5 times with the same alcohol to get out all methylamine.

The collected methylamine.HCl is rather pure, but hygroscopic. You should immediately place it into a sealable vessel after filtering it off.

And it contains maybe some dimethylamine - which we don't want. To remove it, the MeAm.HCl is first dried by placing it in an open dish sitting on anhydrous CaCl2 ("DampRid") in a big sealable container. After 2-3 days of sitting in this improvised dessicator, the meAm.HCl will be bone-dry. Now you place it in a beaker, pour some chloroform (CHCl3) over it and boil it slightly. Decant the hot chloroform into another beaker and repeat 2-3 times with fresh chloroform. Then heat the whole beaker containing your purified methylamine carefully, to evaporate the CHCl3 and dry it. Quickly place in air-tight container after drying. Weigh it.

You now have methylamine.HCl with a purity of >95 percent, with very little ammonium chloride left and no dimethylamine.

I_A

Lief · Mon Feb 21, 2005 10:05 pm

Guest · Tue Feb 22, 2005 2:46 pm

Lief,

Do you have access to that document,
Chemical Abstracts can be hard to get for some members,.

I remember in My Old library, The Chemical Absract books were for public viewing, now they are all locked away,
oh well,

syn

IndoleAmine · Dreamreader Deluxe

BTW the ref for the procedure depicted above is patent DE468895, a variation of the standard Vogel's method with NH4Cl/HCHO...

Hexamine hydrolysis
C6H12N4 + 4 HCl + 6 H2O ---> 4 NH4Cl + 6 CH2O

reductive methylation
2 CH2O + NH4Cl + C2H5OH ---> CH3NH3Cl + H2O + C2H5COOH

As one can see, the hydrolysis provides ammonium chloride and formaldehyde in a 2:3 ratio, whereas the methylation step requires a 1:2 ratio of said reagents. Therefore every 4th NH4Cl molecule remains unchanged under optimum conditions, limiting the theoretically possible overall yield to ~75% calculated from NH4Cl (this is the reason why NH4Cl has to be separated - you'll get back at least one mol of unreacted NH4Cl per mol Hexamine used, in reality often more).

i_a

Lief · Wed Feb 23, 2005 4:35 am

IndoleAmine · Dreamreader Deluxe

Right, the dissolving metal reductions...

This also works very well with CH3NO2 and Sn/HCl BTW. (will provide ref, later)

cublium · Tue Mar 01, 2005 12:01 am

That hexamine method is fairly complicated.I used to make it via ammonium chloride and formalin method.I even wrote a guide with pics and Rhodium hosted it on his page.
Methylamine from ammonium chloride and formaldehyde.
I doubt it has the pics but it should have text

java · Consumer

Please check the search function on the Hive files, there are several threads and discussions on the various methods and the one's most OTC.........java

IndoleAmine · Dreamreader Deluxe

COMPLICATED?? I would rather say you're too lazy to do any calculations and/or measure out some few mls of HCl...

Hexamine is hydrolyzed instantly(!) by aequous HCl to give ammonium chloride (NH4Cl) and formaldehyde (HCHO) - so the only difference between the hexamine and formalin/NH4Cl procedure is that you have to work with toxic fumes (formaldehyde) or just with corrosive fumes in minor quantity (fuming HCl, that is until you dilute it).

Its up to you to buy expensive formaldehyde or just cheap hexamine and HCl (BTW both hexamine and HCl are otc, whereas formalin isn't)

And workup conditions are the same with both variations...

i_a

IndoleAmine · Dreamreader Deluxe

Zinc/formic aicd reduces NO2 to NH2 quite effectively at room temp. in minutes, Lego posted some interesting articles about it at the old hive...

Another option would be to use a noble metal catalyst like Pd/C and formic acid in H2O/MeOH to reduce nitromethane to methylamine, which can be distilled off azeotropically with water or gassed out by adding lots of solid KOH...

And of course the Al/Hg couple to reduce alipathic nitro compounds like CH3NO2 to alkylamines like CH3NH2...

i_a

Lief · Wed Mar 02, 2005 7:27 am

Guest · Thu Mar 03, 2005 5:34 am

good article Lief,

There is always the urea & GAA route,
Very good yield, and both precursor reagents are readily avaiable to even a novelist technition,

syn

icecool · Insistent Chemist

If SnCl2 would directly be available as a chemical to you and you bought it.
What purpose would it have.
To use it insted of Fe/GAA right, and then use SnCl2+HCl but what is the advantage of this?

IndoleAmine · Dreamreader Deluxe

It gives cleaner product and higher yields when doing the nef reaction (1-phenyl-2-nitropropene->phenyl-2-propanone).
(search the hive archive for "another easy way to p2p's" by Barium...)

And you can use it as ink remover... Wink

i_a