mr_bovinejony
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Dichromate overoxidation
Nile red has a video on making propionaldehyde but uses some heated condenser water which adds more complication to the setup. I've made acetaldehyde
by dripping in ethanol to the dichromate solution and the acetaldehyde evaps off as it's formed. This can be done too with propionaldehyde if the
solution is heated below the bp of propanol I assume? Is there a reason nile red does it the opposite way?
Another small dichromate question, can the same system of dilute h2so4 be used to oxidize indole 3 carbinol to indole 3 carboxaldehyde? I've tried
this oxidation with bleach and gaa but got some weird colors, I was thinking this was from impurities in the bleach but maybe too strong of an acid
will hurt the indole somehow
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njl
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I think you will want a much milder oxidant for indole 3 carbinol since indoles are notoriously sensitive to oxidation, even by atmospheric oxygen.
Reflux condenser?? I barely know her!
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mr_bovinejony
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I was thinking of using IBX but I have very little and it took a while to make. Might not have a choice though
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Oxy
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Adding the dichromate to ethanol reduces the amount of side-products. Propanol (which is in high excess during addition) is being oxidized and quickly
removed from from reaction mixture so the risk of over-oxidation is reduced. There are just many alcohol molecules which will undergo the oxidation
instead of aldehyde. When you add alcohol to dichromate it's totally opposite. An excess of oxidizer attacks both alcohol and produced aldehyde and it
results in over oxidation
[Edited on 23-4-2021 by Oxy]
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zed
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Bovinejony... Indoles are a horse of different color.
They don't take kindly to being oxidized, and they are finicky in general. They hate acidic condition.
There have been reports of Indole-3-Acetaldehyde being produced from Tryptophan by the bleach-method
you tried to employ, and maybe those reports are accurate. Maybe.
That procedure, relies on extracting the aldehyde into a non-water solvent, as it it formed. Preventing
further oxidation.
But, I'm gonna think on about that carbinol.
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mr_bovinejony
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Are there any more mild oxidizing agents other than IBX/DMP/TEMPO that might work for it then? Maybe pyridinium chloro chromate would work?
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karlos³
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I don't have the paper on me, but I told you definitely about it, maybe even showed it already to you: IBX gives 98% of the aldehyde on
indole-3-carbinol in just 30min.
Its to me the ideal choice of reagent here, no doubt.
@zed I doubt those methods very much, this aldehyde is very unstable and I don't think this can easily be reproduced in an amateur setting.
Yet the oxidation of indole-3-carbinol to the aldehyde can be very well.
Damn, wish I would remember where I got this paper... I'll ask a friend who might has an idea, otherwise it has to be re-found... 
But for everyone ready to look for it, its IBX and indole-3-methanol among many other alcohols to aldehydes.
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clearly_not_atara
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It seems like activated manganese dioxide would be the first port of call for indole-3-carbinol, since it is also used for the oxidation of indolines
to indoles.
https://www.nature.com/articles/202179a0
https://pubs.rsc.org/en/content/articlelanding/1964/jr/jr964...
[Edited on 04-20-1969 by clearly_not_atara]
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mr_bovinejony
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@carl I do have that paper downloaded like 3 times on my phone, ill have to dig for it. The only reason I don't want to use ibx at this point is
because my potassium iodide is low and don't want to use it all right now
@atara thanks for this! I think I saw a video about activated manganese dioxide somewhere, might be worth a try
The manganese dioxide method has intrigued me even more now that I see it can oxidize benzyl alcohol. Everything is so cheap, it'd be dumb not to try
it. Heres the easiest preparation I found
https://pubs.acs.org/doi/10.1021/jo00836a091
Well that excitement was short lived. The addition of carbon to the boiling permanganate solution didn't produce any frothing at all, even though the
bottle says "laboratory grade activated carbon". On to the next one
[Edited on 24-4-2021 by mr_bovinejony]
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xdragon
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Quote: Originally posted by karlos³  | I don't have the paper on me, but I told you definitely about it, maybe even showed it already to you: IBX gives 98% of the aldehyde on
indole-3-carbinol in just 30min.
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https://pubs.acs.org/doi/pdf/10.1021/jo00127a036
98 %, 8 h. I think this is the one you meant, but the reaction time is longer.
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karlos³
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Yeah, must be it.
I was quite certain about the reaction time though, seems I remembered that wrong 
@mr bj, if you try it with something manganese based, you can at least use the overoxidised indole-3-carboxylic acid for esterification, followed by
5,6-dibromination
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mr_bovinejony
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Oooo don't give me any more ideas! There's already too much on the list 
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