This document deals with the preparation of Methylamine and Methylamine Hydrochloride from non-restricted precursors. Both of these compounds are currently extremely difficult to purchase legitimately or otherwise. This is the fourth major revision of the document and it includes some tasty enhancements to further the range of methods available to the struggling home chemist. Remember, though, that none of these processes are meant for the true novice. You will have to put some effort into learning the chemistry, ok?
Please note that I am not a chemist by trade, but I *have* taken great pains to insure the accuracy of all information, including empirical testing. While this means I am not an authoritative reference, it also means that a non-chemist can put this information to use.
What's New? v1.5: I have tested many variations on the Hofmann process in order to make it more efficient and easier. In my empirical testing, I have come up with several process improvements that make life with Hofmann so much easier and much more efficient to boot. For one thing, I have sucessfully performed it without having to use any ice in the reactants, reducing the volume of reactants by over 50% (and less volume is less one has to distill to get the good stuff). Yield hasn't suffered at all, and though slightly more time is required to perform the first step, distillation has been effectively doubled in speed (good for those of us with 500mL flasks and such to work with). Also, I added a new process that some may find more convenient called the Schmidt Reaction. It is very similar to the Hofmann, but please note that I haven't tested it nearly so much. Perhaps in a future "final touch" version I will put more empirical data into it.
What's New? v2.0: I must warn against selecting the Schmidt reaction to make the product, as my experiences it with it have been less than pleasant. Do try to use a fume hood of some sort if you wish to pursue this otherwise highly attractive method. Also, I have re-written the Formalin/Ammonium Chloride method with a more practical view in mind. This new write-up makes it much more worthy of consideration - live and learn, eh? In addition, I have added another preparation of Acetamide which uses all OTC (well, except for the Calcium Oxide) reagents and is both cheap and easy.
What's New? v2.5: Due to the constant nagging of others, I am including a route based on the reduction of Nitromethane. This route is also applicable to other nitroalkanes (eg - ethylamine from nitroethane) and it gives exceedingly good yields with easy to obtain starting materials (except for the Nitromethane, which is a bit pricey and will require some digging on your part). Of more exciting interest is the preparation based on Hexamethylenetetramine (Hexamine, Methenamine). This route is exceedingly easy and gives essentially a quantitative yield of Methylamine HCl using a ridiculously easy process. Kids, it just doesn't get any better than this, really.
Q1) What is Methylamine or Methylamine Hydrochloride?
A1) Methylamine, or more correctly Monomethylamine, is of formula CH3NH2, a simple primary amine. It is a noxious, acrid gas which is quite nasty and a tad on the explosive side. For this reason, it is usually sold or prepared as it's hydrochloride salt, or as an aqueous solution of about 40% concentration. The HCl salt is in the form of white deliquescent crystals, and is frequently substitutable for the aq. soln. in many synthesis preparations.
Q2) What is this lovely compound used for?
A2) Methylamine/HCl has a number of uses in which it is impossible or highly impractical to substitute. Some examples are:
Q3) Where can I get it?
A3) You can't unless you happen to be in an industry that uses it or are prepared to sign your privacy away to the DEA. That's why this FAQ exists; so you can make it yourself. Besides, if you can't make it with the data provided in here, you have no business messing with it anyway.
Q4) What are the legal implications of having it?
A4) Well, it is required by any chemical supply institution that they take down all sorts of data on anyone attempting to purchase a kilogram or more of either the aqueous solution or the salt, but it has been my experience that *no* place will sell it to an individual in any quantity. I even have a friend who owns his own photography business and he says he couldn't buy any as well. I could go off on a long pedantic spiel about how ridiculous this is, but why bother. Possession of Methylamine is not a felony, in any amount, though you may violate some hazardous waste and/or zoning rules above a certain quantity. It's not the kind of thing you want to store next to your bed, anyway. If you have it in conjunction with other compounds, such as P-2-P or MDP-2-P, then if for some reason the DEA came a'knockin', you could be prosecuted for Conspiracy to Manufacture Amphetamines, which could be damaging to your lifestyle and health (see Code of Federal Regulations 21 for more info).
Q5) Can I make it?
A5) Definitely. If you have half a clue and some reasonable grasp of chemistry fundamentals, you can make a good chunk of methylamine in an afternoon. I am covering five individual processes in this FAQ that I feel are relatively easy but, primarily, because they give good yields with little or no di and/or trimethylamines being formed.
The ones I cover are:
It is possible to make it from completely over the counter materials if one chooses the Hofmann rearrangement and synthesizes the Acetamide from Urea and glacial Acetic Acid (synthesis included as well). As a free bonus, I am including the most common preparation of Anhydrous (Absolute) Ethanol from grain alcohol or denatured alcohol.
Finally, I would be remiss if I did not mention that there are several other processes for producing amines, though I have not treated them. Some other processes to consider among the hundreds are:
For further reference, consult these references:
On to the syntheses...
There are two approaches to producing an amine from an amide using the Hofmann rearrangement reaction. One way is to react the primary amide with an alkaline-halide solution (eg - Sodium Hydroxide and Bromine). The other method is to use an alkaline-hypohalite solution (eg - Sodium Hydroxide and Calcium Hypochlorite). The astute observer will notice that there is *no* chemical difference in the two processes. One produces the Hypohalite in situ, the other uses the Hypohalite itself. Substitution of various halogens/halides/hypohalites/hydroxides is acceptable, but I feel I have picked the best combination of maximal yield and ease of availability. Feel free to prove me wrong ;-). Also, at least one text specifies that Sodium Hypochlorite produces much higher yields than Sodium Hypobromite. This delicious vindication is expected since Chlorine is a more reactive halogen than Bromine. Now, we are going to use Calcium Hypochlorite, in the form of powdered pool shock, because concentrated Sodium Hypochlorite is a rare, unstable creature indeed. Our yield will not suffer in the slightest because of this.
The main example presented will be the alkaline-hypohalite method as it is the easiest to acquire the necessary chemicals. It is of interest to note that the alkaline-halide method is much easier to perform, process-wise, in that it is more forgiving of sloppy technique.
The general theory behind the process is that the hypohalite will convert the amide to a haloamide. This then spontaneously changes to the isocyanate when heated and decomposes to the amine from the water present. In effect, all that happens is that a Carbonyl (CO) group is stripped off the starting amide to yield the corresponding amine. Yields pre-purification are around 80%, post-purification average around 65%. Certain uses of the resulting amine will not require purification, though, so it will be left up to you whether or not to perform those steps.
To make methylamine we start with Acetamide. The general, unbalanced reaction process is thus:
CH3CONH2 + Ca(OCl)2 (CH3CONCl)2Ca++ + H2O then
(CH3CONCl)2Ca++ + NaOH CH3NH2 + Na2CO3
You can scale these reactions up or down within reason. What is reasonable? I can't say, but I have done batches from .01 to 1 mole with no difficulty. The key problems in scaling this reaction have to do with heat gradients in the flask and inadequate stirring. Use your own judgement, keeping in mind that this is *not* an industrial process.
One reference to keep in mind (Thanks to J.W. Smith for sending this one) concerns the first step of the reaction.
Whitmore and Thorpe, J. of the Amer. Chemical Society, Vol 63, April 1941, p1118
"It was necessary to allow several hours for the formation of the N-chloroamide before heating to degradation temperature. With this modification it was possible to prepare methylamine...consistently in 78% yield."
In my experience, this is a *true* statement. Please remember to keep the reactants well iced, though. Now, to begin:
In a large mixing bowl which can contain a smaller stainless steel mixing bowl, prepare an ice bath with water and salt to bring the temperature down to -10°C or so. Setup your glassware for simple distillation with magnetic stirring beforehand because certain steps need to be performed quickly. Use a vacuum adapter to connect to the receiver flask, and attach some rubber or polypropylene tubing to the vaccum nipple to connect to a bubbler setup (a funnel inverted in a beaker, or a plastic aquarium aerator tube). The distilling flask should be sitting in in a stainless steel bowl with nothing in it (you will add pre-heated oil to the bowl).
Next you will prepare three solutions.
This last solution should be prepared slowly as it is quite exothermic. Set all three aside in a freezer. Now prepare the mixing apparatus which will be a stainless steel "mixing bowl" suspended in the ice/salt bath made earlier. We use a stainless steel bowl here so that heat transfer will be maximal, while preventing any corrosive interaction. A glass bowl will not be sufficient for larger scale preparations as it will not conduct heat fast enough to prevent the reactants from going over 10°C (at which point the Haloamide will decompose and you'll have to start over). Take the Sodium Hydroxide solution out of the freezer once it is cool, but not cold.
After the bowl has been sitting in the ice bath for a few minutes, add the Acetamide solution. Stir well until the solution has cooled to -10°C. Now, *slowly* add the Hypochlorite solution to the mixing bowl in bursts of no more than a couple mL while stirring vigorously. If you do this perfectly, there will be no fizzing or bubbling at all. This depends on how cold you keep the mixture, and how slowly you add the pool shock! Realistically, the considerable heat evolution of the reaction will make adding the last few mL a trying task! Keep an additional 50g of ice on hand to throw directly into the mixture if necessary. This solution *may* evolve Chlorine gas so you should obviously perform this step under a fume hood or outside). Keep stirring until it has calmed down and turned a turbid colorless to light green Let it sit for 2 hours, stirring occasionally and making sure that it never gets warmer than 5°.
After the 2 hours is up, add the Sodium Hydroxide solution quickly with stirring. The solution should immediately turn a chalky, milk white. That's because a lot of Sodium Carbonate just got generated. You no longer need be concerned over it's temperature, so you can leave the solution in this state overnight if perhaps the hours have passed by too quickly and you've suddenly realized it's 2:00am.
Preheat a water bath on the stove (or wherever) to about 80°C and place the stainless steel mixing bowl in it. Once the temperature of the solution hits about 65°C, take the bowl out and set aside while stirring all the while. This is where it rearranges, and the reaction is exothermic enough to sustain it's temperature nicely. If you find the temperature climbing past 80°C, immerse the bowl into some cold water briefly. After about 15 minutes the temperature will start to fall, at which point you should transfer the whole mess to the distilling flask. Before you continue you need to choose whether you want to make the hydrochloride salt or the aqueous solution of Methylamine, though.
Heat the flask using an oil bath to 100°C after adding this solution to effect gentle boiling which will drive off the Methylamine as a gas. In my experience, misbehavior is likely to occur at this point. One particular problem to watch out for is the sucking back of bubbler solution (be it plain water or 6N HCl) into the receiver flask. I don't know why the pressure in the distilling flask would go below atmospheric, and therefore cause this to happen, but it has several times with me. Needless to say, this results in a serious mess and *botches* the whole process (I have found a cure for this by using an automotive one-way vacuum valve, like a PCV).
Continue heating the flask contents until you have collected around 100mL of distillate in the receiver.
For the aqueous solution: Place 18mL of cool distilled water into your bubbler setup. The *expected*, not theoretical, yield of Methylamine from this amount of reactants is 7 grams. I have used a plastic aquarium aerator tube as the bubbler with excellent results. Sure beats using an inverted funnel.
For the HCl salt: Do exactly as above except use 6N Hydrochloric Acid. 6N HCl may be produced by diluting 60.4mL of "Muriatic Acid" to 100mL with distilled water. Evaporate the bubbler solution to dryness then add 15ml of water, 10mL 10% NaOH soln. and heat gently to a boil with constant motion until dense white fumes appear. This will remove the Ammonium Chloride. Remove from heat while stirring as it cools down. Pulverize the dry residue, then reflux with absolute Ethanol for several minutes. Filter the refluxed soln. on a heated Buchner or Hirsch funnel, then distill the alcohol off the filtrate until crystals just begin to form. Allow the soln. to cool naturally to room temperature, then cool further in an ice bath. Filter the solution on a chilled Buchner funnel with suction. The yield of Methylamine Hydrochloride should be around 55% of the theoretical.
To clean the white residue off of your glassware, dump some muriatic acid straight from the jug onto them and swirl.
This reaction is quite similar to the Hofmann Rearrangement, but it reacts a Carboxylic Acid with Hydrazoic Acid to generate the desired amine. Like the Hofmann, it has wide application and versatility, yet also has excellent yields in many cases. It will also preserve the chirality of the starting Acid/Anhydride, which is not of interest to us, but an important fact to note. The restrictions on this process are that the starting Carboxylic Acid must not adversely react with either Sulfuric Acid or Hydrazoic Acid. It would be a crime if I didn't also mention that the Schmidt Rearrangement has much greater application than just making amines from carboxylics, but that is well beyond the scope of this FAQ. See Organic Reactions v3 for more details.
To make Methylamine or the HCl salt using the Schmidt Rearrangement, you start off with glacial Acetic Acid. You might be saying to yourself, "Damn, why bother with the Hofmann!" since glacial Acetic Acid is so easy to get, but, there is a drawback... And that is Hydrazoic Acid, which is *not* easy to get. As well, Hydrazoic Acid is extrememly poisonous and should not be handled without a fume hood under *any* circumstances. Really. This is coming from a guy who has no problem distilling Ether solutions in his kitchen, so take it seriously. Why bother, then? Well, because you *can* generate the Hydrazoic Acid in situ using Sodium Azide and conc. Sulfuric Acid. I have not personally tried this because I don't have a powder addition funnel. Anyway, Sodium Azide is not too hard to come by through chemical supply houses and Sulfuric Acid is easy to acquire in the form of Instant Power Drain Opener. This reaction MUST be performed in an area of adequate upward ventilation, or at least with the air flowing away from you.
Theory behind this reaction is:
The intermediates in making amines are isocyanates (O==C==N) just like the Hofmann Rearrangement. The isocyanates are decomposed with water, just like the Hofmann. In fact, there is a lot of similarity between the Hofmann and the Schmidt reactions. Before I detail the synthesis steps, I should note that if you wish to generate the Hydrazoic Acid in the flask by adding Sodium Azide, you might need a powder addition funnel. This bit of equipment is quite pricey and it's likely you won't have one, so the first part of the synthesis details how to make the Hydrazoic Acid separately.
There are three variations on this process you may choose from:
a) Preparation of Hydrazoic Acid
Prepare a paste out of 65g Sodium Azide (1m NaN3) and 65mL of water in a beaker. Add 400mL of either Chloroform or Benzene to this paste (depending on what you have available, but be consistent later on) and stir well. Dump this mixture into a round bottom flask situated in an ice/salt bath, drop in a stirrer magnet, attach a Claisen adapter, addition funnel, and thermometer. Let this mixture cool to 0°C.
Place 49g of cold concentrated Sulfuric Acid into the addition funnel, but only after you make sure the stopcock is turned OFF. Ever so slowly add the acid to the flask, dropwise, such that the flask contents stay around 1°C, and never go over 5°C. This might take a while, be patient. After all is added, pour the flask contents into a separatory funnel (ventilation is absolutely required here) and separate out the aqueous layer. Your HN3 is dissolved in the Chloroform/Benzene layer. If you wish to determine the exact concentration of the acid, you may titrate it, but the reaction generally goes to completion with no secondary hydrazides forming as long as you kept the temperature where I told you to. Some HN3 might have gone to the aqueous layer, but mostly the resulting Sodium Sulfate will crowd it out. The resulting concentration, then, is the moles of Hydrazoic Acid over the the total moles of HN3 and your solvent (Chloroform = 117g/m, Benzene = 78g/m).
b) Making the Amine (All Variations)
Setup your glassware for simple distillation with a claisen adapter, three way adapter, pressure-equalized addition funnel, water cooled condenser, vacuum adapter and receiver flask to catch any condensed solvent vapors.
c) Specifics for Variation 2
Drop your stirrer magnet into the flask and add 250mL of Benzene or Chloroform (take your pick), Next, add .25 moles glacial Acetic Acid (15g) then .5 moles Hydrazoic Acid with stirring. Warm this solution to about 40°C using a water bath. Make sure all joints are air tight. Add 20mL concentrated Sulfuric Acid very slowly. The reaction is mildly exothermic, so take care and watch the temperature. The reaction finishes within 2 hours. The amine is in the sulfate salt form. To convert to the hydrochloride salt form, first add an equinormal amount of 10% NaOH solution and stir well. Next, extract the free amine with ether and bubble HCl gas through it to precipitate out the crystals. Filter to recover.
This is the least desirable of all the processes. The yields are lower than the two rearrangements, and it requires substantial labor to get a decently pure product. Not "labor" as in difficult but "labor" as in a lot of it. I would suggest this only for those who have a large supply of Formaldehyde available to them (note - N. Coffey found formaldehyde at Home Depot - look for "Mildewcide" and dissolve it in enough water to make a 37% solution to depolymerize the paraformaldehyde).
Place 250g of Ammonium Chloride and 500g of technical Formaldehyde (37%, Formalin). Rig the flask for simple distillation such that a thermometer extends into the reaction mixture, and a Liebig or West condenser. Heat the mixture on the steam bath until no more distillate comes over, then turn up the heat and hold the reaction temperature at 104°C until, once again, nothing else comes over. This should take from 4 to 5 hours. The distillate may contain interesting things, so check out footnote 1 for details on what to do with it. Next, the reaction flask should be cooled rapidly to room temperature by immersion into first a warm water bath (60C) swirled, and then an ice bath. Filter the solution on the vacuum Buchner funnel to recover ~62g of Ammonium Chloride crystals. Concentrate the filtrate using moderate vacuum and gentle heat until the volume is reduced to half. Filter the mother liquor once again after cooling quickly to yield a second batch of Ammonium Chloride, ~19g.
Transfer the filtrate to a ceramic evaporating dish and heat on a water bath until a crystalline scum forms on the top. Cool the dish quickly then filter the mess on the vacuum Buchner to yield ~96g of Methylamine Hydrochloride. Concentrate the filtrate once again to obtain a second crop of crystals, ~18g. Concentrate the filtrate a third time as far as possible using the water bath, then store the dish in a vacuum dessicator loaded with Sodium Hydroxide in the bottom for 24 hours. Add Chloroform to the residue left in the crucible to dissolve out Dimethylamine Hydrochloride (distill off the Chloroform to recover - good stuff) then filter on the venerable old vacuum Buchner funnel to yield an additional ~20g of Methylamine Hydrochloride, washing the crystals in the funnel with a small portion of Chloroform (~10mL).
Purification of the Methylamine HCl is in order now, so transfer all of the crude product to a 500mL flask and add either 250mL of absolute Ethanol (see end of FAQ for preparing this) or, ideally, n-Butyl Alcohol (see Footnote 4). Heat at reflux with a Calcium Chloride guard tube for 30 minutes. Allow the undissolved solids to settle (Ammonium Chloride) then decant the clear solution and cool quickly to precipitate out Methylamine HCl. Filter rapidly on the vacuum Buchner funnel and transfer crystals to a dessicator (see Footnote 3). Repeat the reflux-settle-cool-filter process four more times if using absolute Ethanol, or two more times if using n-Butyl Alcohol. The yield of Methylamine HCl should be 100g.
Footnote 1 - The byproducts of the first step are Dimethoxymethane and Sodium Formate.
Footnote 2 - The Methylamine solutions in all steps should be cooled rapidly to promote smaller crystal formation.
Footnote 3 - According to the original document, centrifuging is the most satisfactory method of drying products because of their hygroscopic nature. I suggest warming in an oven on a glass dish then transfering to a vacuum dessicator loaded with either concentrated Sulfuric Acid or Sodium Hydroxide in the bottom. It is not normally necessary to have absolutely dry Methylamine HCl anyway.
Footnote 4 - The solubility of Ammonium Chloride in absolute Ethanol is 0.6g/100g at 15C. The solubility in n-Butyl Alcohol is neglible, even at its boiling point. If you use n-Butyl Alcohol, you will only need to perform 3 reflux/filter operations to obtain sufficiently pure Methylamine Hydrochloride.
References to this section:
The lower nitroalkanes (sometimes refered to as nitroparaffins) are easily reduced by a multitude of systems, but by far the easiest, and also the highest yielding, is the Iron/Hydrochloric acid system. The reaction is:
First, your Nitromethane *may* require purification, especially if it was for "fuel" use. In this case, it needs to be vacuum distilled at a vacuum of better than 100mm Hg. At that pressure, it will come off at ~47°C. Distillation at atmospheric pressure is possible, but I do not recommend it due to the highly flammable nature of the compound and because it's flash point is 42°C. It's your choice.
Assemble a 500mL RB flask with claisen adapter, thermometer down the center to read the liquid temperature, and reflux condenser with a cork and tube leading to a beaker of 1M Hydrochloric acid. Drop a stirrer magnet in, then add 105g of 40 Mesh Iron filings, 225mL of water and 1g of Ferric Chloride. Next, add 35mL of concentrated Hydrochloric Acid ("muriatic acid" is ok). When the bubbling ceases, add 31g of Nitromethane.
Heat the reaction mixture to 100°C and hold for 14 hours. A temperature regulator is necessary if using a heating mantle, else use a large boiling water bath (if you will be doing it overnight, so it doesn't run out).
At the end of this time, allow to cool then add enough 25% Sodium Hydroxide solution to to get the pH above 11. Heat on a water bath or with gentle electric heat to drive the Methylamine off as a gas into the same beaker of Hydrochloric acid used as a trap during the reaction.
Evaporate the beaker contents to dryness on a glass plate in the oven to collect the crystals of Methylamine HCl (hygroscopic!). The yield should be approximately 15g (95%).
Cognate procedure: Setup a flask with reflux condenser in which .25 mol of nitromethane, .38 mol of granulated tin metal and a stirrer magnet have been added. Carefully pour 115mL of 31.45% hydrochloric acid (muriatic acid) down the reflux condenser in 10-15mL increments, waiting for the reaction to settle down before pouring the next aliquot. If the reaction seems to get out of hand (excessive frothing, vapor escaping the reflux condenser, etc...) then quickly slide an ice bath in place until it slackens back down. Once all the HCl has been added, heat the mixture to reflux with an electric mantle for 1hr. At the end of this time, allow to cool, preferably in an ice bath, then add, carefully, a chilled solution of 75g sodium hydroxide in 125mL of water. If the flask contents start to bubble violently you will watch your yield go out the window, so add slowly! Since methylamine readily dissolves in water, you will need to distill the reaction contents carefully to first liberate the 40% constant boiling solution (bp: 53°C) and then the gas itself. The product is best captured by bubbling the distillation vapor into a beaker of hydrochloric acid (use a slight molar excess of HCl to insure no loss). Proceed as above by evaporating the bubbler solution to yield the crystals (take care when evaporating HCl solutions, as the excess acid will vaporize into the air, corroding ovens, lungs, etc...). [Vogel's, pg 892]
Additional notes - Nitromethane is found in high performance RC model fuel, usually as a mixture with methanol and various strange lubricants. One particular brand, found at a local hobby shop, was 55% nitromethane.
Johnson & Degering, J. Am. Chem. Soc., v61, 1939, pp3194-3195
Hexamine, more formally known as Hexamethylenetetramine, is easily and conveniently produced from Formaldehyde and Ammonia solutions. Formaldehyde may be easily produced by depolymerizing, with heat, Paraformaldehyde (the only ingredient in OTC MildewCide). Hexamine is then reacted with Hydrochloric Acid and heated to yield Methylamine HCl in near quantitative yield.
The pertinent equations are thus:
C6H12N4 + 4 HCl + 4 H2O 4 CH2NH3*HCl + 2 CO2
I have serious empirical evidence to believe the second equation is incorrect, but more on that later.
a) Preparation of Formaldehyde
Place 3 3oz packets of Mildewcide into a 1L flask with an electric heating mantle and cork in the neck connected to a gas bubbler immersed in at least 550mL of distilled water. Heat the paraformaldehyde (what is in the Mildewcide) to between 180-200°C (a temp. regulator is absolutely necessary for this step or use a silicone oil bath). The paraformaldehyde will depolymerize making formaldehyde gas in about 91% yield. Alternatively, the gas can be bubbled through the Ammonia solution directly (only for the brave!!!). If the Formaldehyde solution will not be used immediately, 55mL of methanol should be added to it to prevent flocculation (repolymerization).
b) Preparation of Hexamine
454mL of 40% Formaldehyde solution (Formalin) or 490mL of 37% technical grade solution is *slowly* poured into a tall beaker containing 250mL of 28% Ammonia solution. Stir vigorously the entire time. The solution will get hot as the reaction occurs, take care that the Formaldehyde solution is not added too rapidly otherwise it will boil over.
Allow this mixture to react, with stirring, overnight. Evaporate off the water by heating the beaker in a hot water bath. (CAUTION: excess ammonia will be liberated!) The yield of Hexamine should be 140g, white crystals.
c) Hydrolysis of Hexamine
140g of Hexamine is carefully dissolved in 400mL of Muriatic Acid (31.45% HCl) to which at least 100mL of (preferably) absolute ethanol has been added. Add the hexamine slowly while stirring vigorously and with good ventilation as some nasty fumes are produced. Allow all to stir at room temperature for at least 8 hours but preferably 16. The solution will become turbid within several hours of the initial mixing. I *believe* this is the formation of a formaldehyde trimer of some sort and I suspect that the original equation for the conversion of hexamine into methylamine fragments is therefore incorrect. At any rate, filter off this white precipitate which is obviously not an amine salt due to it being fluffy even in Florida's humidity (almost all simple amine salts are hygroscopic). Finally, remove the excess water, hydrochloric acid and freako volatile products by, ideally, heating the liquid at low to medium heat in a porcelain saucepan. Stove-proof glass would be ideal, but stainless-steel, aluminum and copper are definitely not! The concentration can generally be left unattended for a couple of hours, but try to stick around and babysit it at least the first time so you will have a good idea of how long it takes for your particular stove/pots/etc... Also, the methylamine HCl will form a melt if heated too long at which point it will sublimate off. It will then appear as if it's taking forever for the stuff to concentrate when in fact you are merely boiling your product away. After the concentrated slush has become sufficiently "thick", take it off the heat every so often to see if it doesn't soldify, insuring that the water is mostly gone and that not too much sublimation has occured (some is inevitable and even desireable). The yield of Methylamine HCl should be around 200g as white deliquescent crystals. Note, ACS-grade methylamine HCl is colorless. We aren't using ACS-grade production techniques here, so don't expect ACS-grade product. However, the methylamine produced by this method is eminently suitable for the many purposes normally intended and if allowed to sublimate some when heating, no adjustment for "purity" or "water content" need be made in subsequent uses of it.
d) Notes on the process
If the crystals are opaque white and do not deliquesce quickly in air of average humidity (65% rh), they may be contaminated with some Hexamine or some bizarre polymer. Washing 100g of the crude product with 100mL of Chloroform by stirring in a beaker then filtering, repeated as many times as necessary, will remove Hexamine. Methylamine HCl is insoluble in Chloroform whereas Hexamine is at the rate of 1g to 10mL.
It has been determined that the best batch size is to process 70g of hexamine at a time. This is primarily due to the fact that the amount of heat necessary to boil something increases exponentially with the volume. It seems to normally take 4-6 hours to fully concentrate the methylamine solution with a 70g batch but as much as 16 hours to do 200g. Of course, the solution can be split up among pans to evaporate, but try and keep it at 100g expected yield per pan to get the best tradeoff between time and volumetric efficiency.
As a final note, I have been informed that hexamine is available in some areas in the form of "fuel tablets" for small camping stoves. I have received mixed results from various individuals using this so, as the saying goes, Caveat Emptor.
Blazevic, "Hexamethylenetetramine, A Versatile Reagent in Organic Synthesis", Synthesis, pp161-176 (1979)
Urea is a constituent of many fertilizers and so it is easily obtained. Sources have indicated that a 50lb bag can be purchased for $15 in the US. It is of less than ideal purity from this source, so some washing will be in order (with what?). Glacial Acetic Acid is easily obtained from photographic supply stores in high purity and for cheap as well. This reaction produces Acetamide with such purity that the product does not even need to be recrystallized (the reaction goes to completion with no side products). The reaction is:
Place 125g Urea and 125g of Acetic Acid in a 500mL round bottom flask in preparation for simple refluxing with magnetic stirring and without cooling water (or use cooling water heated to about 80°C). Attach condenser, claisen adapter and place thermometer so that the bulb is around 1cm from the bottom, fully immersed. Heat on the mantle gently to bring the temperature of the mixture to 150°C in 20 minutes. The mixture should be refluxing in the condenser, and probably subliming in it as well unless heated "cooling" water is used. Push any crystals back down as necessary. Hold at reflux until the temperature rises to 195-200°C (approximately 1.5 hours) Allow to cool, then rearrange the condenser for distilling (its really preferable to use 80°C water in the condenser). Heat to collect nearly pure Acetamide starting at 200°C with most coming over from 214-216°C. If the product smells strongly of mice (as in the rodents), then recrystallization from warm methanol is in order. To recrystallize, take 50g of Acetamide, dissolve in 40mL warm Methanol, add 100mL Ether to crash it out and allow to stand. If no crystals have formed after an hour or so, gently scratch the inside of the beaker with a glass rod. If your product is only faintly odorous and is colourless to white, then it is considered pure. Melting point is 80.5°C.
Ethyl Acetate is allowed to mix with concentrated Ammonia solution for several days to make Acetamide. This is a very attractive method because all the reagents involved are easy to acquire and cheap.
a) Preparation of Ethyl Acetate from Ethanol and glacial Acetic Acid
Dehydrate at least 100mL of grain alcohol to yield absolute Ethanol. 74mL (58g) will be required. Add this quantity of Ethanol to a round bottom flask with 225g glacial Acetic Acid and 3g of concentrated Sulfuric Acid. Heat at reflux on an electric heating mantle for 12 hours then attach a Vigreaux or Hempel fractionating column to distill off the crude ester at 76-77°C. Change receiver flasks and recover the excess of Acetic Acid, bp 118°C. Wash the first receiver contents with a half volume of saturated Sodium Bicarbonate solution then add 50g of anhydrous Sodium Sulfate (the salt of Sulfuric Acid and Sodium Hydroxide, dried in an oven at >100°C for several hours) and distill the pure dry ester once again. Yield should be greater than 70g.
b) Reaction of Ethyl Acetate and Ammonia to make Acetamide
Add 44g of Ethyl Acetate and 90mL of concentrated Ammonia solution (~28%) to a 500mL round bottom flask with a stirrer magnet. Plug the neck with a thermometer in a thermometer adapter and stir gently for 48 hours or until the mixture becomes homogenous (stop the stirrer occasionally to check). Attach standard distillation apparatus but leave off the receiver flask at first, connecting a short piece of rubber tubing to the receiver adapter which is submerged in a beaker of dilute HCl (10-20%). Heat gently on a mantle to drive off the excess ammonia into the beaker. When no more bubbles come over then attach the receiver flask and commence distilling acetamide from 170°C up, rapidly. Run 80°C water though the condenser to prevent clogging. Once distillation slows to a crawl, remove the receiver flask and set aside in a hot water bath (80-90°C). Clean up the glassware used for the distillation then use the receiver flask as the distilling flask and a glass container with screw-lid top as a receiver. Run 80C water through the condenser as before, and redistill the Acetamide, which should come over completely at 216C using the heating mantle. Yield should be greater than 24g.
Dehydrate 75g of fresh anhydrous Calcium Oxide in a vacuum dessicator for 24 hours (a bit redundant, I know) or heat in an oven at 200°C for 2 hours, then immediately transfer to the vacuum dessicator until use. Setup glassware for simple refluxing with a water-cooled condenser and a Calcium Chloride guard tube. Place 350mL of Ethanol into the flask, quickly add the Calcium Oxide and hold at gentle reflux on the water bath or heating mantle for 6 hours. Allow the mixture to stand overnight, then distill off the alcohol, discarding the first few mL (it may be more convenient to just vent the condenser to the atmosphere for the first couple of minutes after distillation has commenced). Yield should be better than 315mL. Store the absolute Ethanol in a tightly closed glass container as it will pick up water from the air rapidly.