Sciencemadness Discussion Board

Aurin- tricarboxylate synthesis

wg48temp9 - 14-8-2019 at 05:30

In the synth of Aurin- tricarboxylate in the fllowing note what is the purpose of the nitrite?


"Add 4 g of sodium nitrite, in small portions and while vigorously
stirring, to 44 ml of sulfuric acid (sp gr 1.84) contained in a 250-ml
beaker. The nitrite should be added slowly to prevent excessive
evolution of oxides of nitrogen. When all of the nitrite is dissolved,
cool the solution to 10° C. Over a period of 5 to 10 minutes, next add
12 g of salicylic acid, while again stiring the solution.
Cool the solution to 3° C by immersing the beaker in crushed ice,
and add drop wise 3.5 ml of an approximately 37-percent solution
of formaldehyde, while again vigorously stirring.
Since the temperature at this stage must not exceed 5° C
a small thermometer makes a convenient stirrer.
When all the aldehyde has been added, allow the beaker to remain in
the ice bath for about 1 hour and stir the contents every 5 minutes.
The reaction is now allowed to proceed at a reduced temperature for
about 20 hours. A cooling bath is conveniently made by placing a
20-lb block of ice in a tray having approximately the dimensions
12 by 12 by 3.5 inches and filling the tray with ice water. With this
arrangement, when the room temperature is 20 to 25° C,
the temperature of the reacting mixture will increase about 1 to 2° C
during the first 7 hours and then gradually to about 20° C during the next 13 hours."

From Attachment: prep-aurintricarboxylate-jresv21n1p113_A1b.pdf (2.7MB)
This file has been downloaded 275 times

Boffis - 14-8-2019 at 13:13

If you read your own attached paper you will see that they state that the course of the reaction isn't certain but its possible that some of the salicylic acid is converted into a nitroso compound and this condenses with the the first formed methylenedisalicylic acid (assuming it is first formed!).

wg48temp9 - 14-8-2019 at 14:03

Quote: Originally posted by Boffis  
If you read your own attached paper you will see that they state that the course of the reaction isn't certain but its possible that some of the salicylic acid is converted into a nitroso compound and this condenses with the the first formed methylenedisalicylic acid (assuming it is first formed!).


Thanks Boffis I missed that.

wg48temp9 - 15-8-2019 at 11:18

I found a curious note titled:
SYNTHESIS OF THE COVALENT HYDRATE OF THE INCORRECTLY
ASSUMED STRUCTURE OF AURINTRICARBOXYLIC ACID (ATA)

Attachment: cushman1990.pdf (566kB)
This file has been downloaded 214 times

The note suggests that the usual synthesis using salicyclic acid, formaldehyde, sulfuric acid and sodium nitrite produces a polymer of methylene linked aurincarboxylic acid molecules. Its not helpful in understanding what the nitrite does but it does explain the use of 3,3'-dicarboxy-4,4'-dihydroxydiphenylmethane (two molecules of salicyclic acid linked with methylene) in the synthesis of aurincarboxylic acid as described in Org. Synth. 1929, 9, 8 DOI: 10.15227/orgsyn.009.0008.
Attachment: CV1P0054.pdf (337kB)
This file has been downloaded 188 times

[Edited on 15-8-2019 by wg48temp9]