Sciencemadness Discussion Board

Anyone have a simple tetrapropylammonium bromide?

Nitrous2000 - 19-2-2021 at 17:19

Hi folks,

I’ve read the post on the butyl alcohol version but any simple synthesis to the propyl ammonium bromide version?
Can isopropyl alcohol be a starting point?

Thanks folks - I’m over 30 yrs from my chem degrees and I was a P Chem not a cook! ;)

njl - 20-2-2021 at 07:48

I doubt the procedure would be very different for propyl alcohol. I also don't think IPA would be a good starting point unless you're willing to go through an entire process to functionalize the primary carbon.

UC235 - 20-2-2021 at 08:12

No, you'd need to start from n-propanol. Conversion to n-propyl bromide should be fairly trivial and preparation of isopropyl bromide and ethyl bromide found eslewhere on this forum should work well and in high yield.

Tsjerk - 20-2-2021 at 10:49

Tetraisopropyl ammonium bromide would have to go via triisopropyl amine, which is hard to make because of steric hinderance, making a quartenary out of it would be impossible.

karlos³ - 20-2-2021 at 11:44

Tetraisopropylammonium salts are impossible, wikipedia says the following:
Triisopropylamine is notable as being among the most sterically hindered amines currently known.

So there is no way you can alkylate that even further.
If you even get to that, if you look at the wiki article, you'll discover the preparation of the trialkylamine is even not doable via the normal routes.

[Edited on 20-2-2021 by karlos³]

draculic acid69 - 21-2-2021 at 00:49

How is it made if not thru the normal routes?

Texium - 21-2-2021 at 07:45

Easy google

clearly_not_atara - 21-2-2021 at 17:33

I would suggest looking into the paper which originally recommended tetrapropylammonium over tetrabutylammonium for this application:

Since butanol is usually much cheaper and easier to get than propanol, it is probably helpful to know whether you can get away with tetrabutylammonium in this case and what the disadvantages would be.

If you cannot buy n-propanol, any preparation of tetrapropylammonium bromide is going to be rather difficult. You can make propionaldehyde by the pinacol rearrangement of propylene glycol with sulfuric acid, but you will need a few more steps to get tetrapropylammonium.

Tetrapropyl ammonium bromide

Nitrous2000 - 24-2-2021 at 09:32

Thanks for the reply. Seems propyl bromide and tripropylamine are a one step with high yields... but am having trouble sourcing these.

One point I should make here is that my choice of agent is based on a paper detailing a static zinc-bromide (as opposed to the traditional flow-type) battery that uses this as a bromide complexing agent to act as an electrolyte between plates.


[Edited on 24-2-2021 by Nitrous2000]