2HCHO + NH4Cl —> CH3NH2.HCl + HCO2H
Submitted by C. S. Marvel
Checked by J.B. Conant
In a 5-l. round-bottomed flask, fitted with a stopper holding a condenser set for downward distillation and a thermometer which will extend well into the liquid, are placed 4 kg. (3711 cc., 47-53 moles) of technical formaldehyde (35-40 per cent; sp. gr. 1.078 at 20 degrees) (see Note 1 on p. 378) and 2 kg. (37 moles) of technical ammonium chloride. The mixture is heated on the steam bath until no more distillate comes over and then over a flame until the temperature of the solution reaches 104 degrees. The temperature is held at this point until no more distillate comes over (four to six hours). the distillate, which consists of methylal, methyl formate, and water, may be treated as described in Note 1.
The contents of the reaction flask are cooled to room temperature (Note 2), and the ammonium chloride which separates is filtered off and centrifuged (Note 3). The mother liquor is concentrated on the steam bath under reduced pressure to 2500 cc., and again cooled to room temperature, whereupon a second crop of ammonium chloride is obtained. The total recovery of ammonium chloride up to this point amounts to 780-815 g.
The mother liquor is again concentrated under reduced pressure until crystals begin to form on the surface of the solution (1400-1500 cc.). It is then cooled to room temperature, and a first crop of methylamine hydrochloride, containing some ammonium chloride, is obtained by filtering the cold solution and centrifuging the crystals (Note 3). At this point 625-660 g. of crude product is obtained. The mother liquor is now concentrated under reduced pressure to about 1000 cc. and cooled; a second crop of methylamine hydrochloride (170-190 g.) is then filtered off and centrifuged. This crop of crystals is washed with 250 cc. of cold chloroform, filtered, and centrifuged, in order to remove most of the dimethylamine hydrochloride which is present;
[word count above: 306, current date, 6-20-09, time 6:53 a.m.]
after the washing with chloroform the product weighs 140-150 g. The original mother liquor is then evaporated under reduced pressure, as far as possible, by heating on a steam bath, and the thick, sirupy solution (about 350 cc.) which remains is poured into a beaker and allowed to cool, with occasional stirring, in order to prevent the formation of a solid cake (Note 2). The thick paste so obtained is centrifuged, and the crystals (170-190 g.) are washed with 250 cc. of cold chloroform; the solution is filtered and the crystals are centrifuged, thus yielding 55-65 g. of product. There is no advantage in further concentrating the mother liquor.
The total yield of crude centrifuged methylamine hydrochloride is 830-850 g. This product contains, as impurities, water, ammonium chloride, and some dimethylamine hydrochloride. In order to obtain a pure product, the crude methylamine hydrochloride is recrystallized from absolute alcohol (Note 4). The crude salt is placed in a 5-l. round-bottomed flask fitted with a reflux condenser protected at the top with a calcium chloride tube; 2 l. of absolute alcohol is added and the mixture heated to boiling. After about one-half hour the the undissolved material is allowed to settle and the clear solution is poured off. When the alcoholic solution is cooled, methylamine hydrochloride crystallizes out. It is filtered off and centrifuged, and the alcohol used for another extraction. The process is repeated until the alcohol dissolves no more of the product (about five extractions are necessary). In the flask 100-150 g. of ammonium chloride remains, making the total recovery of ammonium chloride 850-950 g. The yield of recrystallized of recrystallized methylamine hydrochloride is 600-750 g. (45-51 per cent of the theoretical amount, based on the ammonium chloride used up in the process) (Notes 5 and 6).
[ At this point I'll put in my notes. Paraformaldehyde is the name given to a solid form of formaldehyde; it is usu used. Absolute alcohol is 100% ethyl alcohol, "absolute" means definitely dry. Denatured alcohol can mean different things; you have to read on the "SD-40" or whichever "SD" is the one ('specially denatured") suitable. You're doing the cleanest work, but . . . lead and mercury are sad to make somebody take and water isn't, but water will prevent the reactions from occurring sometimes. Notice they go through the utmost effort to recover the maximum amount. This is understood by all, and performed by experiment, to decide which process to use, and what advance is real, to increase the yield over the former process. This is the bullshit of the numbers people declare as to percent. This is the whole reason for the above-quoted publication. Chemists were not supposed to be "estimated EPA mileage" guys. Would you pass up a gas station because you calculated that your car should go further? You can't knock 5% off these numbers. If you can't do it like they said you are going to get lower numbers. Lastly, you were not supposed to work in a lab to get this stuff. You just go out and buy it. MeNH2.HCl comes in a 5-lb. brown bottle, MeNH2 gas comes in a cylinder, if you steal a cylinder it has to be the right one. You can't really possess a cylinder. It is like a shopping cart. To have it legally it is about 50 cents a day, with gas. The regulators are also specific to the gas. I am thinking about hydrogen. I had one. The cart and the chains are an integral part. Gas cylinders are the one freight to know how to move. Actually, it is not very far up in chemistry to order cops around. They turn into M.P.s and you are at war. Fritz Haber got tired of the way he was treated as a Jew and gassed the English. Louis Feiser liked cats more than people and invented napalm, naphthalene on a palmitate, sticky little flaming gel dropped on villages all over Vietnam. He invented more things. Fritz Haber must have been his hero. Lastly, again, (I need some duct tape over my mouth), what I am on is caffeine (my drug of choice), you get-methylamine gas 40% in water. This is why it is no good; some tweak opened it up to smell it and the gas is gone. If you know ammonia, you could believe that a little probably smells like a lot. Past lastly, the Bhopal incident (65,000 deaths) resulted from (probably) some onsite tweak engineers trying to obtain a bucket of methyl isocyanate, which hydrolyzes (changes immediately with water) to methylamine, and it got away from them and the whole underground tank went. Notice the name methamphetamine. In order to say I wouldn't mind ethamphetamine, I must use the name N-ethyl amphetamine. Ethylamine is a liquid.]
[This post has a first entry which is the Organic Syntheses preparation. Here is another one geared to the people's method: http://designer-drugs.com/pte/184.108.40.206/dcd/chemistry/methylamine.chemhack.html. Edit added 12-24-10 at 8:01 am by SEB]