09-13-01 23:27
No 213225
There was a process given on Rhodium's page where dimethylamine is synthesized by refluxing DMF with HCl for over 6h and doing an a/b extraction. However, in Rhodiums Methylamine FAQ, another synthesis is given. Simply react methylamine HCl with formaldehyde. Now doesn't that sound better? My question is how I should go about doing this. Could I just boil methylamine HCl in an access of paraformaldehyde in water above 115deg for a few hours? What would you suggest? Here's the section from Rhodium's FAQ:
Methylamine hydrochloride condenses with formaldehyde to form dimethylamine. If formaldehyde is present in excess, at least some of the methylamine is converted to dimethylamine. If too little formaldehyde is present, the methyleneimine polymerizes to its trimer, (CH2=NH)3. Trimethylamine is never formed, as long as the temperature of the solution never exceeds 110°C. With an excess (4 moles) of formaldehyde, enough water and a reflux temperature of 115°C, dimethylamine is the main product, as the temperature rises, more dimethylamine is formed. Dry heating of paraformaldehyde and ammonium chloride produces trimethylamine through reaction of dimethylamine with formaldehyde, giving rise to tetramethylmethylenediamine and formic acid, and the base further reacts with HCl, giving trimethylamine hydrochloride and methyleneimine hydrochloride. A mixture of HMTA and HCl boils between 105 and 110°C, while NH4Cl/CH2O boils at 115°C. No temperature control is really necessary in the former case, as long as your heating plate isn't too hot. If the reaction is carried out at a lower temperature, less dimethylamine is formed, and the yield is higher. Vacuum reflux and distillation can yield at least 95% yield, in contrast to the 45% gotten at 104°C.
(Old P2P Cook)
09-14-01 07:03
No 213378
From Vogel:
Proceed as in the preparation of methylamine hydrochloride Post 209576 (terbium: "Re: Methylamine; So many problems? Is it the Altitude", Newbee Forum) using 200 gram of ammonium chloride and 400 gram of formalin, and heat the mixture at 104°C until no more fluid distills. Cool to room temperature and filter off the ammonium chloride (ca. 50 g): add 300 g. of formalin to the filtrate, return the solution to the distilling flask, heat until the temperature reaches 115°C and maintain it as nearly as possible at this temperature until no more liquid passes over (about 3-4 hours). Concentrate the residue in the distilling flask on a water bath until a scum appears on the surface of the hot liquid. Cool to room temperature and filter off the solid (ca. 32 g.; impure methylamine hydrochloride containing about 25% of ammonium chloride). Pour back the filtrate into the distilling flask and heat to 120°C until a sample of the liquid, on cooling, becomes semi-solid. Transfer it to a vacuum desiccator charged with sodium hydroxide pellets and leave it there for 2 days. extract the residue with hot chloroform and filter; on cooling, crystals of dimethylamine hydrochloride separate. A further crop can be obtained by evaporating the filtrate to about half its original volume. The yield is 120 g.
(Hive Bee)
09-14-01 18:14
No 213530
Thanks! Surley the vacuum desicator can be removed from the proceedure and perhaps DCM can replace chloroform, correct?
(Old P2P Cook)
09-15-01 06:38
No 213770
Don't know. I would expect that, in this case, the difference in solvent properties between DCM and chloroform might be significant. It may not be necessary to extract with chloroform if a product that is mostly dimethylamine is acceptable; a titration using a pH meter would tell you the purity of your dimethylamine.
(Hive Bee)
09-15-01 18:31
No 213842
Or using phenothalene. I remember that stuff from chem class. You carfully add you base with stiring untill the the last drop causes the solution to remain purple. Thanks again for the info. I think this is one of the only dimethylamine synth threads.
(Ubiquitous Precursor Medal Winner)
09-17-01 13:10
No 214306
Spell "phenolphthalein" backwards. In case you don't want to synth dimethylamine, the weed killer (herbicide) with the trade name diazinon comes as the dimethylamine salt. Basify and boil it out, catch it in dilute HCl, titrate back to neutral with base, boil down to fractionally crystallize it out of the salt water. If it's still traded; herbicides and insecticides have short market lives, as their specific horrors are uncovered.
turning science fact into <<science fiction>>
(Hive Bee)
09-17-01 16:57
No 214364
Is it the HCl salt or what?
(Hive Bee)
09-18-01 03:41
No 214549
I went to the garden store today and found several brands containing various dimethylamine salts. I bought the one that was the highest in concentration and had only the dimethylamine salts as the active ingreadiants (a total of 13%). To my delight, when I mixed a sample with NaOH, there was an obvious reaction and an ammonia smelling gas was produced. If this is pure DMamine gas, than one can easily make the very usefull anahydrous solution of DMamine in ether by simply boiling away the volitals in this stuff, mixing it with a large access of NaOH (an access to help absorb the water), bubble it through ether and dry over MgSO4. Could this gas possibly be anything other than dimethylamine? Here are the ingredients:
Mecoprop, dimethylamine salt
2,4-D, dimethylamine salt
Dicamba, dimethylamine salt
On the MSDS for this product (found on company's site), those are the only listed ingrideants so I assume the other 86% is water.
(Hive Addict)
06-16-04 01:00
No 513655
To 75 g (1.03 mol) of dimethylformamide in a 500 ml roundbottom flask was slowly added, portionwise, 160 g 6N aqueous hydrochloric acid. Caution, this was a very exothermic process! The flask was fit with a condensor and the mixture was refluxed for 7 hours. Dimethylformamide hydrolyses to dimethylamine and formic acid, so the fumes were led outside in case some carbon monoxide formed due to decomposition of HCOOH.
The mixture was vacuum distilled at the fridge pump until a white mushy solid was left in the distilling flask. This was sucked as dry as possible on a Buchner funnel and transferred to a dessicator, where it was dried over CaCl2 for a couple of days. There was obtained 59.3 grams of dimethylamine hydrochloride as sparkling white crystals, which is a yield of 70% .
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