Sciencemadness Discussion Board - Over-oxidation of aldehyde to ketone

Over-oxidation of aldehyde to ketone

metalayer - 7-10-2014 at 20:05

I have experimented with the over-oxidation of an aldehyde to a ketone and had some positive results. I'm now looking for ways to improve the yield. I found a reference saying that the over-oxidation of alkenes was greatly increased by the addition of base (Oxidation in Organic Chemistry - W Trahanovsky)...would this work with aldehydes?

Any other suggestions for increasing the amount of oxidative cleavage would be appreciated.

Thanks!

Crowfjord - 7-10-2014 at 21:15

An aldehyde cannot be oxidized to a ketone. Do you mean oxidation of an aldehyde to carboxylic acid, or over oxidation of a secondary alcohol to a ketone?

CuReUS - 8-10-2014 at 00:25

maybe its a condensation reaction ,with one aldehyde losing water and joining the other aldehyde to form a ketone?

Chemosynthesis - 8-10-2014 at 00:38

Quote: Originally posted by CuReUS

maybe its a condensation reaction ,with one aldehyde losing water and joining the other aldehyde to form a ketone?

I don't see how that would work, as the recipient would become an alcohol or further elimination to the alkeno portion of an enal. The terminal aldehyde would not gain an alpha carbon because chain elongation would be on the side with the enol(ate), which requires an alpha carbon.

CuReUS - 8-10-2014 at 01:05

i am not saying that the aldehyde will lose water by removing both of its own hydrogen

suppose you have 1 molecule of acetaldehyde and one molecule of formaldehyde
now you want to make acetone so the formaldehdye comes adjacent to the acetaldehyde and loses 1 hydrogen(the terminal one,but both are the same) ,one oxygen and takes the terminal hydrogen from acetaldehyde to make water and joins with acetaldehyde .but is that even possible ?
maybe you could do something like that with a metal catalyst which will form some kind of complex with the acetaldehyde and formaldehyde to help it to lose the water that way

DJF90 - 8-10-2014 at 01:11

You should look at the Aldol condensation. Acetaldehyde and formaldehyde are a special case, giving pentaerythritol after several iterations and a final reducion.

Chemosynthesis - 8-10-2014 at 02:44

Quote: Originally posted by CuReUS

i am not saying that the aldehyde will lose water by removing both of its own hydrogen

suppose you have 1 molecule of acetaldehyde and one molecule of formaldehyde
now you want to make acetone so the formaldehdye comes adjacent to the acetaldehyde and loses 1 hydrogen(the terminal one,but both are the same) ,one oxygen and takes the terminal hydrogen from acetaldehyde to make water and joins with acetaldehyde .but is that even possible ?
maybe you could do something like that with a metal catalyst which will form some kind of complex with the acetaldehyde and formaldehyde to help it to lose the water that way

As DJF90 says, this is a special case, though I like your thinking. Formaldehyde has special chemical properties that allow it to participate in reactions such as the production of trithiane and Mannich bases that other aldehydes cannot, but because of its chemical eccentricity in these regards, it would have to be specified beforehand with another reactant for me to start thinking that way.

metalayer - 8-10-2014 at 05:09

Quote: Originally posted by Crowfjord

An aldehyde cannot be oxidized to a ketone. Do you mean oxidation of an aldehyde to carboxylic acid, or over oxidation of a secondary alcohol to a ketone?

My understanding is that oxidation of highly enolizable aldehydes (with a large excess of a strong oxidizing agent like KMnO4) will produce the ketone as a minor product and the carboxylic acid as the major.

Dr.Bob - 8-10-2014 at 07:31

You need to give some specifics for this to make any sense. Can you draw the reaction or give some idea what aldehyde and what ketone that you get, since how you would get a ketone from oxidizing an aldehyde is not clear to most. What would the R group on the ketone be?

CuReUS - 8-10-2014 at 07:59

Quote: Originally posted by DJF90

You should look at the Aldol condensation. Acetaldehyde and formaldehyde are a special case, giving pentaerythritol after several iterations and a final reducion.

to make pentaerythritol from acetaldehyde and formaldehyde you need to do a crossed aldol condensation first which forms trihydroxymethyl acetaldehyde(THA), which then undergoes a crossed cannizzaro with formaldehyde as THA has no alpha hydrogen

and to wrap it all up nicely ,treat pentaerythritol with HNO₃/H₂SO₄ mixture to get PETN

all in a good day's work

metalayer - 8-10-2014 at 08:28

Quote: Originally posted by Dr.Bob

You need to give some specifics for this to make any sense. Can you draw the reaction or give some idea what aldehyde and what ketone that you get, since how you would get a ketone from oxidizing an aldehyde is not clear to most. What would the R group on the ketone be?

Apologies for being cryptic. This was discovered by a friend and I don't want to compromise his possible patent. I will ask him for permission to share more.

forgottenpassword - 8-10-2014 at 09:06

Your friend discovered that he can oxidise an aldehyde to a ketone and wants to patent it? Pull the other one.

[Edited on 8-10-2014 by forgottenpassword]

CuReUS - 8-10-2014 at 09:17

Quote: Originally posted by Chemosynthesis

As DJF90 says, this is a special case, though I like your thinking. .

chemosynthesis ,could you check whether acetyl chloride could be prepared by the method i posted in this thread,please if you are not too buzy

http://www.sciencemadness.org/talk/viewthread.php?tid=32991&...
my post is second last

Chemosynthesis - 8-10-2014 at 15:12

Quote: Originally posted by CuReUS

chemosynthesis ,could you check whether acetyl chloride could be prepared by the method i posted in this thread,please if you are not too buzy

http://www.sciencemadness.org/talk/viewthread.php?tid=32991&...
my post is second last

I will look. No neex to single me out, as there are many here who have forgotten more than I will ever know in terms of chemistry. Please don't hijack someone else's thread next time, though.

Oxidative C–C Bond Cleavage of Aldehydes via Visible-Light Photoredox Catalysis

metalayer - 11-10-2014 at 08:36

http://pubs.acs.org/doi/abs/10.1021/ol303437m

May be of interest to those that stated oxidative cleavage of aldehydes to ketones was impossible in my topic the other day.

Crowfjord - 11-10-2014 at 08:49

Ah, that makes much more sense! The wording was just confusing us. This probably could have gone into that same thread, though.

metalayer - 11-10-2014 at 09:35

Quote: Originally posted by Crowfjord

Ah, that makes much more sense! The wording was just confusing us. This probably could have gone into that same thread, though.

This isn't the method I used. What I did was far less involved/expensive. I just thought people might appreciate the reference and wanted to show in general terms that aldehyde -> ketone is possible.

Chemosynthesis - 11-10-2014 at 09:42

Quote:

http://pubs.acs.org/doi/abs/10.1021/ol303437m

May be of interest to those that stated oxidative cleavage of aldehydes to ketones was impossible in my topic the other day.

I do not mean this argumentatively or pedantically, however....
Respectfully, no one stated that specifically (only one poster said something equivalent), you were asked for a mechanism, you didn't give a page number for the reference on alkaline conditions, and there is a large distinction between photoredox reactions and potassium permanganate oxidations. You said

Quote:

Then you were asked for a mechanism. No one stated it was impossible to turn an aldehyde to a ketone, just that your description didn't make sense.

That said, thank you for posting. Photoredox reactions are supposed to be highly unusual in that they can allow for some interesting reactions. I would love to hear more about your experiments and hope you continue posting.
I anticipate learning a lot from this as this is an area of chemistry I know little about, other than some conference presentations on environmental degradation of pollutants, and it is intriguing to see it applied.

[Edited on 11-10-2014 by Chemosynthesis]

solo - 11-10-2014 at 19:49

Reference Information

Oxidative C–C Bond Cleavage of Aldehydes via Visible-Light Photoredox Catalysis
Hongnan Sun, Chao Yang
Org. Lett.
2013, 15 (3), pp 624–627
DOI: 10.1021/ol303437m

<a href="http://www.freeimagehosting.net/commercial-photography/"><img src="http://i.imgur.com/ZlGCZjL.jpg" alt="Commercial Photography"></a>

Abstract
The visible-light mediated oxidative C C bond cleavage of aldehydes has been achieved in good yields at ambient temperature and open to air
using Ru(bpy)3Cl2 (bpy = 2,20-bipyridine) as the photoredox catalyst. Moreover, we further demonstrated the application in a tandem Michael/
oxidative C C bond cleavage reaction.

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[Edited on 12-10-2014 by solo]

[Edited on 12-10-2014 by solo]