Keras
National Hazard
Posts: 794
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
Sodium benzoate + ammonium chloride → Ammonium benzoate + Salt?
I just wonder if the reaction above is likely to take place.
I want to get ammonium benzoate to make benzamide by dehydration, and from that aniline using a Hofmann rearrangement (it’s more a proof of
concept).
However, the idea of combining directly benzoic acid and ammonia doesn’t really work, because benzoic acid is only soluble in hot water whereas for
ammonia it’s exactly the opposite. So my idea was to use the salts instead.
Thanks!
|
|
|
EF2000
Hazard to Others
Posts: 118
Registered: 10-5-2023
Location: The Steppes, now trapped in the forest zone
Member Is Online
Mood: wrooom
|
|
Quote: Originally posted by Keras  |
However, the idea of combining directly benzoic acid and ammonia doesn’t really work, because benzoic acid is only soluble in hot water whereas for
ammonia it’s exactly the opposite.
|
It works, apparently. In this paper in Thermochimica Acta, ammonium benzoate is prepared by dissolving benzoic acid in concentrated ammonia
(25%, I guess): https://doi.org/10.1016/j.tca.2010.01.021
Attachment: 1-s2.0-S0040603110000298-main.pdf (349kB)
This file has been downloaded 31 times
Wroom wroom
|
|
|
clearly_not_atara
International Hazard
Posts: 2704
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Benzoic acid is more soluble in water when there is some kind of alkali present to deprotonate it. I expect that adding solid benzoic acid in small
portions to aqueous ammonia with stirring and chilling would achieve the desired results.
[Edited on 04-20-1969 by clearly_not_atara]
|
|
|
Keras
National Hazard
Posts: 794
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
| Quote: Originally posted by clearly_not_atara | | Benzoic acid is more soluble in water when there is some kind of alkali present to deprotonate it. I expect that adding solid benzoic acid in small
portions to aqueous ammonia with stirring and chilling would achieve the desired results. |
Well I tried that initially, proceeding from the same rationale, bubbling ammonia produced from boiling a commercial 30% solution. It simply didn't
work. The acid never dissolved entirely. I evaporated the resulting solution, got some white crystals and when I tried to pyrolyse them, all I got was
tiny (and beautiful) flakes of benzoic acid, which sublimed out of the flask. It was a flat out fiasco.
|
|
|
bnull
Hazard to Others
Posts: 184
Registered: 15-1-2024
Location: Between the Atlantic and the Pacific Ocean
Member Is Offline
Mood: Sleepy (again)
|
|
In a solvent in which both sodium and ammonium benzoate are soluble and sodium chloride is not. Ethanol or methanol, for example.
| Quote: Originally posted by Keras | I want to get ammonium benzoate to make benzamide by dehydration, and from that aniline using a Hofmann rearrangement (it’s more a proof of
concept).
However, the idea of combining directly benzoic acid and ammonia doesn’t really work, because benzoic acid is only soluble in hot water whereas for
ammonia it’s exactly the opposite. |
Someone else had the same issues with benzoic acid almost four years ago:
| Quote: Originally posted by SplendidAcylation |
A few months ago, I got quite excited when I found out that benzonitrile could be made by dehydrating benzamide, which can be made via thermal
dehydration of ammonium benzoate, using P2O5.
The dehydration of the amide should be just the same as dehydrating formamide or acetamide, and the preparation of the amide itself, by heating the
ammonium carboxylate, should also be as easy as the other ones, however the preparation of the ammonium benzoate is a lot more straight forward than
either the formate or acetate, because the benzoate is much more stable, and less soluble in water.
So, with these things in mind, and a reckless desire to waste phosphoric anhydride, I went about it.
I made the ammonium benzoate simply by dissolving benzoic acid in an excess 25% ammonia solution.
The dissolution was extremely slow, so I ended up recrystallizing the benzoic acid first to increase its surface area; then it dissolved fairly
quickly.
Once dissolved, I heated the solution in a dish on a water bath, once the water was all gone I had an almost quantitative yield of the salt.
The dry salt was then sealed in a glass tube and heated, immersed in sand, to around 200c for an hour.
Upon cooling, I found that the dry white salt had turned into a light brown, wet, waxy substance, presumably benzamide.
The substance melted readily, and was thus poured out of the tube.
|
Another route you can try is aminolysis of a benzoate ester to give benzamide directly. But then, where would be the fun?
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
|
|
|
Keras
National Hazard
Posts: 794
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
| Quote: Originally posted by bnull |
In a solvent in which both sodium and ammonium benzoate are soluble and sodium chloride is not. Ethanol or methanol, for example.
|
Fair enough. But water would be more than sufficient. I did some eyeballing, and 1 mol of benzoic acid + one mol of ammonium chloride in 175 mL of
boiling water should do the trick. There will be some ammonium benzoate lost in the process, but the salt should remain in solution. Not a big deal,
given the price of the reactants.
| Quote: Originally posted by bnull |
Another route you can try is aminolysis of a benzoate ester to give benzamide directly. But then, where would be the fun? |
I have no experience with aminolysis. But then, why bother create some ester, as you say.
|
|
|
DraconicAcid
International Hazard
Posts: 4280
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
Esters are easy enough.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
Keras
National Hazard
Posts: 794
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
Sure.
Well at this point I've ordered benzoyl chloride. So I can both make esters and benzamide directly by treating with ammonia :p
Still, I’ll try the first route.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
