------------------------------------------------------------------------------- Al/Hg Reductive amination under pressure ------------------------------------------------------------------------------- Psychokitty: The following submission is one which strange indeed. It is a synthesis of methamphetamine via the standard Al-Hg reduction of P2P and methylamine, but with a twist: it does so under 3 atm of H2 pressure. The information is limited in the abstract and obviously, to get more information, those interested in the method with have to refer to what looks like a French patent. Fr. patent #844,228. The CA abstract is vol. 34, 7544 sec 7. Interestingly, in the reaction is used less solvent (considerably less!)and would you believe it? The reaction uses much much less activated Al!!! Stirring would thus be a cinch, as would final work-up! My guess is that the hydrogen necessary to effect the increased pressure would be generated in situ from the hydrolysis of the Al. My guess is that a modification of this reaction could be accomplished using the your SRV, spiceboy. All you would need is to constantly monitor the amount of H2 generation in the vessel and its pressure. Agitation would be necessary, but the length of the reaction may be short due to the small amount of Al being used in the reaction. Anyway, here are the experimental details: Phenylacetone 14 parts, ethylether 50 parts, 15 parts of alcohol containing 20% methylamine, 5 parts of H2O, and 2 parts activated Al are reacted together under 3 Ibs of H2 pressure. Work-up is standard. ------------------------------------------------------------------------------- Chemhack: The best thing about this is that you could vastly reduce the amount of methyalmine that escapes into the atmosphere. The ketone would be reacting under a blank of H2 and Methlamine gas and you could just shake or swirl the damned vessel! ------------------------------------------------------------------------------- Psychokitty: Now that I have more time, I can elaborate a little more about the ways which this reaction might successfully be carried out. First of all, the ether used in the reaction might be unnessary and actually dangerous for the initial trial run. I personally would substitute everclear in its place and omit the 5 parts water that is needed in the reaction. Secondly, the interior of the SRV is going to initially contain atmospheric gas (nitrogen, oxygen, etc.), so to limit its presence to a minimal degree, I would squeeze the bottle as much as possible so that when the hydrogen is formed, there will be room for it to expand. One problem I forsee with this reaction is in regard to the alcoholic 20%MeNH2. The amount of water used in this reaction is very specific, so I figure the alcoholic amine solution will have to be made from scratch. Luckily, this can easily be accomplished by dripping an aqueous solution of MeNH2 onto solid KOH and then pumping the evolved gas into a container holding a suitable amount of alcohol. Details to this proceedure can be found somewhere in the first three volumes of ORGANIC SYNTHESES. Look under "methylamine" in the index of each volume. Find the relavant pages, and there will be somewhere in one of them, experimental details to the sythesis of the alcoholic methylamine solution mentioned above. Another solution to this problem would be to use the more common MeNH2-HCl and neutralize it ala Shulgin. Unfortunately, that method of neutralization probably won't work because of the volume of water that would necessarily accompany the 25%NaOH base solution. A much better alternative would be to use the more up-to-date neutralizing agent used in similar reductive amination reactions, triethylamine. It is a stronger base than methylamine, so it should work well. It's also miscible with water and alcohol, and boils in the >80degC range, making it even more ideal. On the downside, its presence may take up valuable solubility space in the already minimized alcohol volume, and thus might account for significant methylamine losses from the reaction mixture. Perhaps an increase in solvent volume might help to avoid this predictable complication. As for the standard SRV set-up, depending on the length of the reaction, I think the empty 2 liter coke bottle will do just fine. However, if the reaction time-frame exceeds 2 hours, then another reaction vessel will have to be suitably fashioned out of some other common container -- one that will have to allow magnetic stirring of the solution. As for the classic use of a tire valve, I suppose it could be made to work, but continuous monitoring of the H2 pressure build-up would be absolutely mandatory. Therefore, it may be best to build a modification of Fester's hydrogenation device using a pressure gauge, along with the necessary adapters used to connect all the external gas control devices to the SRV-bottle's cap (epoxy-glued, if necessary) which can then be efficiently connected to the SRV by screwing on the cap. The side fitting to the adapter will be connected on each side by two swag-lock air valves. The cost of making these few changes to the original SRV design (which I christen the AA-SRV [Activated-Aluminum-Spiceboy-Reaction-Vessel; or, Amalgamated-Aluminum-Spiceboy-Reaction-Vessel -- whichever one is fine with me, take your pick]) based on prices listed in the industrial catalogue sitting before me, is somewhere in the neighborhood of 25 dollars. Maybe less if you can find the stuff locally. I've seen many of the parts at various hardware stores in my city. For illustrations of the general way an AA-SRV can be arranged, refer to Fester's SOMM under the chapter describing reductive amination using the bomb. Beware of Fester's classic recommendation of using a champagne bottle as a suitable hydrogenation reaction vessel. Not only is there not even the smallest instruction on how to attach the pressure gauge and valves securely to the top of the bottle, but, because the bottom of the bottle is curved, magnetic stirring is next to impossible to do. This is because the curvature impedes the stir-bar's ability to rotate, thus prohibiting the creation of a satisfactory vortex. With the new AA-SRV design, H2 pressure should be easy to monitor. As it builds beyond 3 atm (30 Ibs, I think), excess gas pressure can be released by turning open slightly one of the swag-lock valves. Once the pressure is back down to 3 atm, the valve can be shut. If pressure builds up again, the same proceedure can be repeated. Eventually the reaction will die down, but as far as how long it is supposed to continue is a question best answered by a careful examination of the original French patent. Luckily, anyone who can read Spanish can probably make at least a rough translation. French chemistry articles are in my experience pretty easy to decipher, as all of the important shit (weights, yields, etc. etc.) are pretty much written in the same fashion as chemistry papers printed in English. So someone with access to foriegn patents -- please, get ahold of the French patent in question! One other perplexing issue: What can one reasonably expect the reaction temperature of this new method to be? Does the initial point of the reaction consist of a brief but dramatic rise in temperature, or does an initial temperature of about 25degC remain constant throughout the course of the reaction? And if there is an initial rise in temperature, how long does it last? Ten minutes? One hour? Regardless, would it be vigorous enough to warrant keeping an ice bath nearby? And if significantly high enough, would this increase in temperature complicate the concommitant maintenance of the gas pressure at 3 atm? Well, I'm just dying to know. But unfortunately, I don't have anywhere near the resources necessary to even try to attempt this new Al-Hg reduction method. Those of you presently working with Al-Hg as a means to reducing your precious MD-P2P to the ever-desirable MDMA, you should consider taking seriously the information contained in this post. ------------------------------------------------------------------------------- ChemHack: From my limited experience with Al/Hg I'd say that the pressure would build up almost immediatly upon adding the NaOH solution to the amalgam/h20/MeAm.HCl mixture. The initial burst of pressure would be methylamine gas. Dumping a mole of NaOH onto a mole of MeAm.HCl is gonna release a freakin' mole of gas in very short order. That gas that won't just stay in the alcohol/h20. ------------------------------------------------------------------------------- Labrat: The procedure in this patent is almost the same as the one used by bikers to make Ice. They just dumped some P2P, methylamine solution, alcohol and activated aluminum in a big steel barrel and sealed it. Then they rolled the barrel into a river. Sometimes the barrel exploded, especially when the bikers didn't roll it fast enough into the river. I really like this procedure, thanks! ------------------------------------------------------------------------------- Psychokitty: Just wanted to post another possibly useful variation to the pressurized Al-Hg method. Since agitation of the AA-SRV might be a bit difficult and hard on the arms, I thought it might be useful to lower reaction time and increase the yields by applying ultasound to the sceme of the reaction. Ultrasonic bath cleaners are readily obtainable for about 300 to 400 dollars. Some, maybe cheaper. I know this is a big start-up expense, and the money issue is going to turn alot of you all off right away, but there is alot of information to support the idea that using an ultrasonic bath cleaner as a way of applying ultrasound to chemical reactions, markedly makes a positive difference. All you would have to do is immerse the AA-SRV during the reaction phase into the ultrasonic bath cleaner's water solution and allow the reaction to continue as usual. The ultrasound will cause cavitation, and possibly optimize the reaction conditions. No stirring or agitaion will be required. Don't believe in the potential? Refer to the following citations if you don't: Journal of Chemical Education Vol. 63, No.5, pp.427-429, May 1986. "Sythesis with Ultrasonic Waves" And the review "Sonochemistry -- The Use of Ultrasonic Waves in Sythetic Organic Chemistry" published in SYNTHESIS 1989, pp.787-813. The first reference is particularly relevant as it exemplifies the application of ultrasound to a hydrogenation experiment whereby the reduction was achieved WITHOUT any pressure at room temperature. The catalyst was Pt/C. ------------------------------------------------------------------------------- Labrat: Since the pigs already know about the Al/Hg reduction method according to this French patent, it's only fair we share this with everybody, right? And it is a real good method, the ketone, methylamine and aluminum are used in equivalent amounts and the yield of meth is good. Since the SRV everybody knows pressure reactions, creating the 3 atm hydrogen pressure shouldn't be a big problem. Here it is. Enjoy! French patent no. 844,228: "PROCESS FOR THE PREPARATION OF AMINES" It's already known that reducing hydroxyketones or polycarbonylic compounds with activated aluminum and ammmonia derivates leads to formation of the corresponding aminoalcohols. This reaction is favored because of the fact that hydroxyketones and polycarbonyls are apt to form relatively stable imines. The present invention is about preparing amines by reduction of ketones in the presence of ammonia (derivates) with the aid of activated aluminum and water. Because ketones don't form stable imines with ammonia (derivates), one should not attend to this, but use a relatively moderate reductive procedure, so the ketones can be transformed in the corresponding amines. The resulting products of this procedure are important pharmaceuticals. The preparation is representative for other pharmaceuticals. Example 1: To 14 g phenylacetone dissolved in 50 g ether is added 15 g 20% alcoholic methylamine solution, another 50g ether, 5g water and 2g activated aluminum. The mixture is put under a hydrogen pressure of 3 atm. The reaction is done when all the aluminum has been consumed. The aluminum hydroxide is removed by filtration and the filtrate is extracted with hydrochloric acid. By neutralising with alkalic solution 14 g of crude base is obtained. Distillation gives the pure phenylisopropylmethylamine. Example 2: [irrelevant} Example 3: To 20 g phenylacetone dissolved in 150 g ether, a solution of 10 g allylamine in 50 g ether and 7 g activated aluminum is added. In three portions is added 15 g water. At the same time one stirs vigorously under reflux. After the reaction is done, the aluminum hydroxide is filtered off. The residue is distilled to give phenylisopropylallylamine. Example 4: To 28 g phenylacetone in 100 g ether is added a solution of 20 g benzylamine in 25 g ether, then 5 g of activated aluminum and 10 g water. The mixture is stirred and secured under a pressure of 3 atm. hydrogen. After completion of the reaction, the aluminum hydroxide is filtered off and the residue distilled under reduced pressure to give phenylisopropylbenzylamine. -------------------------------------------------------------------------------