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Author: Subject: TEMPO substitute?
chloric1
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[*] posted on 29-5-2005 at 05:49
TEMPO substitute?


OK I have recently taking interest in the alternative organic reactions involving TCCA and Oxone as environmentally sound and safe alternatives to traditional oxidants and halogenating reagents. Not to mention the extensive OTC availability of these reagents.:D

The problem? Several reactions such aas conversion of amines to nitriles with TCCA involve TEMPO. This is an exotic catalyst that is virtually unavailable to most home experimenters. The Merk index states the this compound is a stable nitroxide and is actually a "radical trap". With that is mind, I don't feel a simple substitution with benzoyl peroxide or MEK peroxide would work. I someone more experienced in organic synthesis could explain the mechanical happenings in TEMPO mediated reactions and suggest alternatives, I think we could have a worthwhile investigation on our hands.;)

[Edited on 5/29/2005 by chloric1]




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[*] posted on 29-5-2005 at 07:56


If I remember corectly TEMPO is prepared from its amine version 2,2,6,6-tetramethylpiperidine by some kind of oxidation (perhaps with H2O2 or peroxyacids?).

Well, 2,2,6,6-tetramethylpiperidine is not OTC, but a similar compund 2,2,6,6-tetramethylpiperidin-4-one can easily be prepared from ammonia and acetone by letting the mixture of both stand for a month or so and then vacuum distilling the wanted product. I tried this once and it works nice. It can be made from very cheap chemicals in large amounts.

The only problem is how the additional carbonyl would interfere in the oxidation to the TEMPO analogue and how such an 4-keto-TEMPO would work as catalyst in radical oxidations. Given that the 4-hydroxy-TEMPO (aka TEMPOL) has some similar use as a radical trap, than perhaps the 4-keto-TEMPO would work as well.




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chloric1
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biggrin.gif posted on 29-5-2005 at 08:34
Absolutely splendid!


If you could briefly describe the ketoTEMPO synthesis or provide academic information of the synthesis of ketoTEMPO I would greatly appreciate it.

Stupid question but what is a "radical trap"? How or why does it function? As opposed to a simple free radical initiator such as benzoyl peroxide of coarse.




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[*] posted on 29-5-2005 at 15:03


I can't give you a literature references as I based my synthesis exclusively on a mention in an very old Czech book from the early beginning of the 20th century where it was said that ammonia and acetone yield 2,2,6,6-tetramethylpiperidin-4-one after the work up of a mixture left standing some time (or some similar short note without any further reference). The reaction mechanism is a simple double condensation of acetone-imine on acetone followed by cyclisation.
I’m sure you can find something on the preparation in the patents as this product is really not that obscure as it sounds by name.

My notes on that experiment are partially lost so I will try to reconstruct by memory. I left standing for a few months a mixture of 200ml acetone, 100ml 25% ammonia and about 1g of ammonium acetate (or acetic acid) in bottle. I later forgot about it otherwise one month should be more than enough, in fact I remember already after a week or two the mixture become red. This mixture was vacuum distilled. The acetone and water that came over first were discarded. The fraction boiling over from 60°C – 120°C (not sure anymore about the temperature) was collected, washed with brine and distilled once more, but this time over a shorter temperature interval. If I remember correctly some 40g of a yellow oil was obtained. It is only partially miscelable with water, soluble in acids and smells like… well, like most amines.

From here on to “4-keto-TEMPO” I found a reference where Oxone is used:
http://dx.doi.org/10.1016/0040-4039(95)01053-K

Radical traps are those compound who can “catch a radical” by forming a very stabile one. In case of TEMPO and similar oxylamines, they are more stabile because of the particular electronic configuration of the R2N-O* radicals, but here furthermore also because being surrounded by four methyl groups which hinder access to it (no dimerisation can hapen). Hence the OH hydrogen in TEMPO is very easily abstracted by any other radicals. Google around for a more thorough explanation.




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[*] posted on 29-5-2005 at 19:50


I know BHT, the food preservative, forms a very stable oxy radical. It is used as a radical trap to prevent food from going rancid. The phenol oxygen's hydrogen is readily abstracted by a radical and the oxy radical is stabilized by the aromatic ring. The ortho t-butyls sterically hinder the oxy radical. If BHT would be suitable for this, BHT is very OTC.
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[*] posted on 30-5-2005 at 05:30
Your help is more than appreciated


How could I thank you enough? After all that is what this forum is all about. I have to wait until tomorrow to acces the article though because I only have access to online journals from work. But, I must say, the process looks promising. Could other nitroxides do the same thing as TEMPO? In the next few months I will have to do the research here with my own chems. Also, considering lack of reference about condensation of ammonia with acetone followed by cyclation, I will have to test different variables to this. It is hard to believe that mixing ammonia with acetone and waiting a few weeks is the only option.



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[*] posted on 16-6-2005 at 13:01
Followup


Hey check this out this has been sitting two weeks now. Keep in mind the following, first I only mixed 100ml of acetone with 100 ml of 28% ammonia, second, the bottle was open for several days as I did not have the correct size stopper!:( I since procurred the stopper from my local hardware store!:cool: and I added the 100 ml acetone needed.

If you look at the picture you can see the bright red color along with some solid particles. Are these part of multiple condensation reactions? The ammonia odor is quite a bit diminsihed and there is absolutely no hint of acetone.

[Edited on 6/16/2005 by chloric1]

[Edited on 28-1-2007 by chemoleo]

DSCN1598.JPG - 59kB




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[*] posted on 18-6-2005 at 12:18


Yes, I remember that viscious red stuff floating in the mixture (just as on your picture). But it is not really crystaline in my experience. You will see when you will be distilling the stuff that it will form two layers as soon as a little acetone comes over.
I forgot to mention that the vacuum in the distillation was aplied only after the acetone came over. But beware that lots of ammonia will came over at this stage so you better drive the gass somewhere out or in the sink running water (I simply loosely attached the vater jet pump tubing in such a way that it sucks air as well, thus still keeping the normal pressure but sucking noxious gasses).
A considerable amount of an orange-red resin remains in the distillation flask. The distillate must be redistilled as it is still not pure (probably still containing some of the not-yet-cyclisized H2N-C(Me)2-CH2-CO-CH2-C(Me)2-NH2 ).




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[*] posted on 19-6-2005 at 09:57
Interesting developement


Nicoderm- Out of boredom the other day, I came across the following patent. I searched under "triacetoneamine" as it is easier to remember. The proceedure sounds promising. It is identical to what we are already doing the only modification is the use of a Ca containing zeolite as a catalyst. Since sodium zeolites are effective ion exchangers, that proceedure would not be to tricky. I have seen the "lab grade" zeolite pellets for removing ammonia from fish tank water but I do not know what zeolite it is. I assume it would be the same as water softeners.



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[*] posted on 19-6-2005 at 09:58
A link to the patent


I guess I could attach the link to the patent to.:D

Cannot attach link but it is patent US6646127

[Edited on 6/19/2005 by chloric1]




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[*] posted on 19-6-2005 at 13:33


Nice patent with many further references. But I don't think it is very worthwhile to search for any special zeolites even if they are that effective. Unless you already have them or are that easy to obtain, off course. The improvement seams to be in the cyclisation which then happens already in the liquid phase. But you will have to distill the product anyway, though perhaps then one distillation would be enough for the crude product.
But given that both acetone and ammonia are so cheap any complications in using special reagents or catalysts is simply too much of a fuss.

I added some ammonium acetate to be the source of ammonium cations which can then transfer the proton to the acetone imine (Me2C=NH) and make it more electrophylic for the condensation. But even without an acidic catalyst the reaction proceed the same as you noticed (though it is slow I admit).

Another acidic catalyst which might work almost as good as the zeolites is silicagel. This might be worth trying as it is so cheap.




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[*] posted on 26-1-2007 at 22:30


From a patent

Seems simple enough.
Example 1

A suspension containt 11 g ammonium chloride and a mixture
of 340 g acetone and 64 g of methanol is saturated over the
course of 12 hours at 13 degrees to 17 degrees with ammonia
gas. The resulting colorless oil is subsequently diluted with
350 g acetone, and maintained, with stirring, for 15 to 20 hours
at 50 - 55 degrees. Excess solvent is removed in vacuo, and
36 g of water is added to the red residue. The
crystallization occuring at 0 - 5 degrees is completed by 2
hours' stirring. The result is 286 g of
2,2,6,6-tetramethyl-4-oxipiperidine hydrate. Melting point 55-60 degrees in the form of slightly yellow crystals.


Wow. The reactants are definitly OTC and the conditions
(ie temperature) are pretty mild. This seems very doable.

[Edited on 1/27/2007 by guy]

[Edited on 1/27/2007 by guy]

Attachment: triacetone amine.pdf (264kB)
This file has been downloaded 1054 times





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[*] posted on 27-1-2007 at 00:11


What does one do with this stuff?

Did "saturade" mean saturated?

And please forgive my ignorance, I come here to learn as well as share, what is TCCA?
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[*] posted on 27-1-2007 at 01:04


Quote:
Originally posted by chemrox
What does one do with this stuff?
It is a precursor for making TEMPO a very useful selective catalyst for oxidizing things.

Did "saturade" mean saturated?

YES

And please forgive my ignorance, I come here to learn as well as share, what is TCCA?
Trichloroisocyanuric acid




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[*] posted on 27-1-2007 at 01:15


Is that a mannich reaction?
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[*] posted on 27-1-2007 at 11:38


Yeah kind of.

And about the ammonium chloride, could ammonium sulfate be subsituted?

[Edited on 1/27/2007 by guy]




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[*] posted on 27-1-2007 at 12:13


Nearly any ammonium salt will do. I used ammonium acetate since that was what I had nearby. That patent method uses ammonium chloride. But the point is in the catalytic effect of the weakly acidic ammonium cation (NH4+) while the anion part does not play much of a role except for solubility issues (ammonium sulfate will not be very soluble in the reaction mixture unless you use the aqueous ammonia method).
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[*] posted on 27-1-2007 at 15:15


can you use a primary amine in that reaction to get n-sustituted 2,2,6,6, tetramethyl piperidine-4-ones?
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[*] posted on 27-1-2007 at 15:19


I think so, but then you can't oxidize the subsituted amine to form the nitroxide radical.



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[*] posted on 27-1-2007 at 19:06


there was some big discussion about this a while back for use in the prep of variants of 1-propionanilido-4-substituted piperidines.
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[*] posted on 28-1-2007 at 14:08


Nicodem, what did your triacetoneamine smell like? I put some ammonia, acetone, and ammonium sulfate in a glass bottle and put a cap on it. I heated at around 50 degrees for 24 hours. The solution was red. Now Im boiling off some water and this smell came out: a very sweet but has an amine odor to it. Is this the right odor?


EDIT:

I attatched a picture of the distillate...Is it too yellow? Should it not be a solid?

[Edited on 1/29/2007 by guy]

[Edited on 1/29/2007 by guy]

P1010007.JPG - 38kB




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[*] posted on 29-1-2007 at 00:16


Here is a pdf reference to the use of tempo (the 2,2,6,6, tempremental piperidine whatchacallit). It is useful for hte oxidation of alcohols according to the reference.

http://www.erowid.org/archive/rhodium/pdf/alcohol.oxidation....
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[*] posted on 29-1-2007 at 13:56


Should the triacetoneamine form a complex with bisulfite, since it is a ketone?



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[*] posted on 29-1-2007 at 14:14


It was several years ago so I don't really remember the smell, except that it was amine-like, but not nearly as unpleasant as piperidine. I guess your description fits. I only identified the compound as "triacetoneamine" from its chemical properties and approximate boiling point during the vacuum distillation with the aspirator (lit. values: 84-88°C at 15 torr; 102-105°C at 18 torr). I remember that the liquid was yellow at the beginning, but after a couple of months deteriorated by air oxidation into some red vicious oil.
Also according to one reference, triacetoneamine can form a monohydrate.

Otherwise, here are two other references for the synthesis of 2,2,6,6-tetramethylpiperidin-4-one:
US2002128482 : 23% yield, 17h/25°C, aq. ammonia, acetone, zeolites (this patent is particularly nice since it also gives a literature review with references to other methods)
Synthetic Communications, 26(19), (1996) 3565-3569 : 65% yield, ammonia, acetone, catalyst

I don't know if it forms a bisulphite adduct, but ketones often do not form very stabile bisulphite adducts unless they are of R-CO-Me type.
If you plan to oxidize it to 4-keto-TEMPO let me know so I can provide you some references.

[Edited on 29-1-2007 by Nicodem]




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[*] posted on 29-1-2007 at 14:46


Quote:
Originally posted by Nicodem
It was several years ago so I don't really remember the smell, except that it was amine-like, but not nearly as unpleasant as piperidine. I guess your description fits. I only identified the compound as "triacetoneamine" from its chemical properties and approximate boiling point during the vacuum distillation with the aspirator (lit. values: 84-88°C at 15 torr; 102-105°C at 18 torr). I remember that the liquid was yellow at the beginning, but after a couple of months deteriorated by air oxidation into some red vicious oil.
Also according to one reference, triacetoneamine can form a monohydrate.

Otherwise, here are two other references for the synthesis of 2,2,6,6-tetramethylpiperidin-4-one:
US2002128482 : 23% yield, 17h/25°C, aq. ammonia, acetone, zeolites (this patent is particularly nice since it also gives a literature review with references to other methods)
Synthetic Communications, 26(19), (1996) 3565-3569 : 65% yield, ammonia, acetone, catalyst

I don't know if it forms a bisulphite adduct, but ketones often do not form very stabile bisulphite adducts unless they are of R-CO-Me type.
If you plan to oxidize it to 4-keto-TEMPO let me know so I can provide you some references.

[Edited on 29-1-2007 by Nicodem]


Thanks for the information. Yes I am planning to oxidize it. I heard it can be done with peroxyacids (oxone?). Those references would be nice. Thanks

I wonder how the zeolite works?

[Edited on 1/30/2007 by guy]




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