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The Hive => Newbee Forum => Topic started by: 3_4_BumbleBee on August 29, 2004, 11:01:00 AM

Title: Separation of P2P/2-Phenylpropanal. wich Oxidant?
Post by: 3_4_BumbleBee on August 29, 2004, 11:01:00 AM

Swibb did the rearrangement of Hydratropic Aldehyde to P2P with H₂SO₄. Now he wants to seperate the P2P from the 2PP.
Which oxidant should he use for the oxydation of the aldehyde to phenylpropanoic acid? and in wich manner is the oxidation done?
i would suggest to use potassium permanganate, because its OTC here. the reaction mixture is ca 80ml in 500 ml dietylether as solvent, how much oxidant will be needed? is it possible to "over-oxidize"?

Title: Hydrotropic Aldehyde to...... P2P ....Oxidation ?
Post by: java on August 29, 2004, 11:59:00 AM

Since the oxidant won't affect the P2P it doesn't matter , but then read for yourself and be convinced....java

Post 456420 (https://www.thevespiary.org/talk/index.php?topic=8882.msg45642000#msg45642000)

(java: "RE: Hydrotropic Aldehyde....", Methods Discourse)

https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenylacetone.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenylacetone.html)

Title: Not exactly true
Post by: yei on September 07, 2004, 11:04:00 PM

KMnO4 is potent stuff. Use with care, or it probably will eat up your P2P.

Probably just use it neutral and cold. You will know it's done oxidizing when the color of the solution stays pink.

Title: We will try it next weekend!
Post by: 3_4_BumbleBee on September 09, 2004, 09:19:00 PM

We will try it next weekend! but i don´t know how this oxidation will be done. 2PP and P2P are not water soluble both. kmno4 is....
will i have to make an aqueous KMnO4 solution and shake it in a separatory funnel for a while with the P2P-mixture until the violet color of the oxidizer disappears in the aqueous layer, add again KMnO4 solution, and so on???
the acid wich then appears is water-soluble and is removed so at the same moment. this would be my idea how this oxidation is done. or am i wrong?
BB

Title: Just tried the reaction myself.
Post by: Bandil on September 09, 2004, 10:32:00 PM

Just tried the reaction myself. Havn't measured yields yet, but will do so in the course of the weekend and make a writeup correspondingly.

Anyhow, you need to slighty alter your procedure. Simply extracting with water wont do the trick. Try this procedure:

- Wash the ether extracts with aq. sodium bicarbonate to remove acid traces (an acidic environment could cause over oxidation of the P2P).

- Titrate the cold ether phase with saturated KMnO₄ solution. Cool the ether / water phase in an ice bath while dripping in the permanganate. This prevents over oxidation.

- Once a purple color remains, the solution is poured into a sep funnel. Let it separate for a few hours. The Mn(IV) precipitate will settle at the bottom as brown sludge. The ether phase is floating on top as a quite "tanned" phase. Isolate the ether.

- Wash the ether phase with a dilute solution of NaOH in water. This converts the acid to the salt, which is water soluble. Drain of the water phase and wash the ether once more with pure water.

- Work up as usuall (dry ether, strip and distill).

Regards
Bandil