Sciencemadness Discussion Board - diethylamine hydrochloride synthesis question.

diethylamine hydrochloride synthesis question.

chemist1243 - 18-11-2019 at 15:58

Okay, so I hydrolized some DEET with NaOH to get a mixture of freebase DEA, ethanol, and some toluene derivatives, as well as probably some other amines. The free base DEA was added to a RBF, put in and ice bath, and HCl was added drop wise. (Note that this was a two necked flask, so I had to cap on neck off with a stopper to prevent vapor clouds of DEA hydrochloride from escaping.) as soon as the HCL was added, a white cloud of vapor formed. I highly doubt that this wasn’t DEA hydrochloride particles, because it had a burned plastic/rotting fish odor.

Once the PH of he solution became acidic, the vapor was allowed to sink back into the liquid until the mixture became clear.

I have this currently sitting in a 500ml beaker with a bag and rubber band sealing it off.

My question is: how would one go about getting the DEA hydrochloride from the mixture? I was think about boiling it off, but I don’t know weather my hotplate could ignite any vapors. I don’t have a vacuum pump or fume hood, so I’m not sure if boiling it off is an option. My next thought would be to just distill off the liquid. What should I do?

Btw, if you want the exact procedure for getting the DEA hydrochloride from DEET, I can post it here. If my yield is high though, I may patents my method, though I’m not sure.

Pumukli - 19-11-2019 at 00:12

Boffis did a nice work on DEET hydrolysis with NaOH a few weeks ago.

What you got is a mixture of diethylamine-hcl, nacl, water, ethanol, unreacted DEET, m-toluic-acid and maybe some o-toluic acid as well.

Diethylamine as a free base is more useful (usually) than its salts. Why the fuss? Why didn't you distilled straight diethylamine off from the still basic reaction mixture? This way you could get the freebase (maybe as a solution in water) and from that making the hydrochloride is fairly straightforward. (The salt is very hygroscopic, mind you.)

If you evaporate water from your mixture in its current state (no, the vapours won't ignite if you do it carefully, hotplate temp max. 150 C), you will got a sticky crystalline mass of various compounds. Then you may try solvent extraction of the toluic acid(s), but the diethylamine-hcl and NaCl separation won't happen...

Actually the way to go is: basify the mixture, distill off the volatile amine, acidify the remaining mixture and purify the toluic acid(s), if you want.
My suggestion is try to follow Boffis's steps!

Edit: typos

[Edited on 19-11-2019 by Pumukli]

chemist1243 - 19-11-2019 at 09:54

the reason im not interested in freebase is because its too difficult to keep safely. is hella volitaile, the vapors crawl along surfaces, and it reeks like rotting flesh. id rather have a nice, sold, non-volitile mass than a liquid, that way i can free base the DEA when the time comes. ill go check out the synth boffis posted. thanks for the help.

Pumukli - 19-11-2019 at 10:14

Not to mention that freebases tend to get oxidized and darken more easily than the salts, absorb CO2 from air, etc.

I tried to "conserve" my dimethylamine as a salt exactly for these reasons but abandoned the idea because the salts were either too hygroscopic or sublimed during drying. Now I have this amine as a 8-9 M water solution in a well stoppered bottle. (No amine smell detectable if I sniff around the cap.)

Boffis - 19-11-2019 at 15:14

Hi chemist1243, as Pumukli says have a look at my recent posting on the diethylamine synthesis thread. I am currently working on a write-up for the "pre-publication" section but in the mean time here are a few notes on my "best method". I carried out the hydrolysis in distillation apparatus and collect the the amine vapour in a calculated quantity of dilute HCl. At the end of the hydrolysis this solution is evaporated down to dryness then the heat is increased until it fused and then cooled; to my surprise there was practically no loss due to volatalization of the amine hydrochloride. The cooled mass solidifies into a solid mass of brownish crystals. These are deliquescent so have to be stored out of contact with moist air. The free base can then be extracted by a second distillation of the diethylamine hydrochloride with 30% NaOH solutions. When the crystals are placed in a distillation flask and the NaOH solution added slowly the crystals react slowly with little heat being generated. On warming the contents of the flask will liquify and separate into two layers the upper layer consists mainly of the amine. The two phases can be separated in a separating funnel (not a nice method, v smelly) or by distillation. The amine distils over between 55 and 59 C as a clear colourless liquid with a sharp ammonia like odour. It is easily store in a glass bottle with a screw cap and PTFE liner. Carried out carefully the yield based on the original DEET is about 80-85%.

If you want the hydrochloride then on the second distillation place a calculated quantity of 15% HCl in the receiver to capture the amine and then evaporate down to fusion of the salt as before or until the first solid appears on the surface of the liquid, cool to <70 C and pour over the solution twice its volume of absolute ethanol and allow to crystallise, filter dry etc.

This is the product from 95g of DEET, 30.67g, about 42.5ml or about 84% yield of fairly pure, colourless diethylamine.

I shall probably use my diethylamine to produce emdite or sodium diethyldithiocarbamate.

chemist1243 - 22-11-2019 at 13:51

Quote: Originally posted by Pumukli

Not to mention that freebases tend to get oxidized and darken more easily than the salts, absorb CO2 from air, etc.

I tried to "conserve" my dimethylamine as a salt exactly for these reasons but abandoned the idea because the salts were either too hygroscopic or sublimed during drying. Now I have this amine as a 8-9 M water solution in a well stoppered bottle. (No amine smell detectable if I sniff around the cap.)

Okay, I think ill just try storing it in freebase form. How long do you reckon this stuff lasts when stored properly?

Pumukli - 22-11-2019 at 20:48

I'd like to (boldly) say that indefinitely, though I only have 15 months experience. It is still transparent though in a green glass bottle and if it started yellowing I could hardly detect any change at this point. I'd rather not open it to examine more closely.

Btw. if it ever gets too discolorated I'll redistill the whole stuff and it will be as good as is now.

Boffis - 23-11-2019 at 04:29

I have a bottle of diethylamine from Reynold and Branson Ltd of Leeds and they haven't been in business for more than 40 years and the amine is still clear. The only thing it might do over the years is to absorb CO2 but this requires water too, so providing you keep the bottle closed when not in use I don't think it will decay at all. When I use liquid amines I usually distil them from KOH pellets, this takes out water and CO2 but I only do this when these contaminant are a problem and then just before use.