[contra]

Hey everyone,

I've been searching around quite a bit for the mechanism behind the synthesis of peroxycarboxylic acids from carboxylic acids and peroxides. I've searched google for a couple of hours and the forum to no avail (perhaps I'm poor at it though, forgive me in advance if that's the case).

Anyway, this is my proposal, it seems pretty simple/straightforward and was wondering if anyone had input on it. I'd really appreciate it!

[discodermolide]

Hey everyone,

I've been searching around quite a bit for the mechanism behind the synthesis of peroxycarboxylic acids from carboxylic acids and peroxides. I've searched google for a couple of hours and the forum to no avail (perhaps I'm poor at it though, forgive me in advance if that's the case).

Anyway, this is my proposal, it seems pretty simple/straightforward and was wondering if anyone had input on it. I'd really appreciate it!

I doubt it is a radical process. Try protonation of the peroxide by the acid with elimination of water and subsequent attack of the acid on the OH+ to give the peracid.

[contra]

@discodermolide:

I figured radicals would form before ⁺OH in this mechanism.

[stevet]

Courtesy of Wikipedia: The Organic Synthesis procedure to synthesise mCPBA uses "hydrogen peroxide in the presence of magnesium sulfate, aqueous sodium hydroxide, and dioxane, followed by acidification."

Maybe this can guide your thinking. Also makes protonation of the hydrogen peroxide unlikely as the reaction is in basic medium.

[discodermolide]

Courtesy of Wikipedia: The Organic Synthesis procedure to synthesise mCPBA uses "hydrogen peroxide in the presence of magnesium sulfate, aqueous sodium hydroxide, and dioxane, followed by acidification."

Maybe this can guide your thinking. Also makes protonation of the hydrogen peroxide unlikely as the reaction is in basic medium.

I was responding to the mechanism he posted not the reaction conditions which were not presented.

[contra]

I figured the ⁺OH ion would be much higher in energy than  the radicals formed in this reaction, although I understand the mechanism you presented. Do you have any literature to support your claim discodermolide?

Does anyone else have any input on this mechanism?

Again, I appreciate all of your *delete me*

[Honclbrif]

No homolytic cleavage or OH⁺ necessary. Run through Fischer Esterification using R-OH, then replace all the R's with OH's.

[discodermolide]

No homolytic cleavage or OH⁺ necessary. Run through Fischer Esterification using R-OH, then replace all the R's with OH's.

The Fischer esterification is acid catalyzed, as I suggested

[discodermolide]

I figured the ⁺OH ion would be much higher in energy than  the radicals formed in this reaction, although I understand the mechanism you presented. Do you have any literature to support your claim discodermolide?

Does anyone else have any input on this mechanism?

Again, I appreciate all of your *delete me*

What is the source of your radicals?
As to the posted reaction conditions, H2O2 decomposes under basic conditions to oxygen and water

[Honclbrif]

You're right, its not "Fischer Esterification", that was my mistake. However, you can draw an equally valid base catalyzed esterification reaction too. Just don't ask me where the equilibrium lies. It like transesterification, but you eliminate OH- instead of an alkoxide. Pretty much the same deal in this reaction. HOO- is the nucleophile  tetrahedral intermediate  OH- is the leaving group.

[nox]

I too doubt that OH⁺ would form to any appreciable extent. However I do think a concerted S_N2 type substitution on protonated H₂O₂ by the carboxylate is feasible.

[discodermolide]

I too doubt that OH⁺ would form to any appreciable extent. However I do think a concerted S_N2 type substitution on protonated H₂O₂ by the carboxylate is feasible.

I think my proposed mechanism shows this approach, I just broke it down into its component parts, if it is OH⁺ or H₂O₂⁺ the result is the same

[408]

What is the source of your radicals?
As to the posted reaction conditions, H2O2 decomposes under basic conditions to oxygen and water

No, not always.

35% peroxide, conc.NaOH, precipitates semi-soluble sodium peroxide as a hydrate.  I forget how many hydration waters.  Just needs to be kept cold.

a) acidic: protonate OH on carboxylic acid, make it a leaving group for the attack of the peroxide
b) basic : presumably a COOH is more acidic than H2O2, so COO- will be present, which would make O2- the LG, which seems very unlikely.
c)radical: unlikely.

Not sure what this OH+ stuff is....

[contra]

What is the source of your radicals?

The peroxide?

[Sepelio]

Those radicals look horrendously unstable. I'd try for one of the other options that has been presented.