dome13
Harmless
Posts: 30
Registered: 29-6-2019
Location: Hungary
Member Is Offline
|
|
Weird precipitate (tin-carbonate?)
Hello!
I am currently synthetising p-aminobenzoic acid from p-nitrobenzoic acid. The reducing agent was SnCl2 x 2 H2O in absolute ethanol. After refluxing I
diluted with water and basified with NaHCO3. This caused a white precipitate, tin(IV)-carbonate. After vacuum filtration I placed the filtrate in a
warm place in order to dry. On the next day I was suprised, that the volume was drastically reduced and it got a yellow-amber like color. It is a side
note what I found interesting: immeditially after filtration, it has a physical properties like vaseline or cold fat.
So, my quiestion is, is this how tin(IV)-carbonate supposed to look like after drying, or is it something else?
|
|
njl
National Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 609
Registered: 26-11-2019
Location: under the sycamore tree
Member Is Offline
Mood: ambivalent
|
|
I don't think tin carbonates are stable and instead decompose into oxides. You probably have a tin oxide/hydroxide contaminated with your target
compound and precursor.
Reflux condenser?? I barely know her!
|
|
dome13
Harmless
Posts: 30
Registered: 29-6-2019
Location: Hungary
Member Is Offline
|
|
It seems to reasonable. Thank you for your answer!
|
|
Amos
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 1406
Registered: 25-3-2014
Location: Yes
Member Is Offline
Mood: No
|
|
I don't think tin is oxidized all the way to the +4 oxidation state; I believe you have tin(II) hydroxide, which often forms a gel, colored brown with
oxidized impurities from your p-aminobenzoic acid.
|
|
Boffis
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 1850
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Its possible that you have incomplete reduction and some hydroazobenzoic acid (white)has formed which then oxidizes to azobenzoic acid (orange-red),
on exposure to air, mixed in with the hydrated tin IV oxide.
|
|
dome13
Harmless
Posts: 30
Registered: 29-6-2019
Location: Hungary
Member Is Offline
|
|
Thank you for your replies!
The reduction indeed was not completed, I got about half of the expected yield.
On the next step, where I made benzocaine, the solution didn't clear up fully on reflux. Altough I got a good yield, the melting point was way too
high compared to literature. The anesthetic effects was negligible too.
I planning to do the synthesis again and try to avoid these little mistakes.
[Edited on 27-2-2021 by dome13]
|
|