Sciencemadness Discussion Board

TEMPO 2,2,6,6-Tetramethylpiperidine 1-oxyl

weilawei - 19-3-2018 at 12:46

I ordered some TEMPO to experiment with oxidation of primary alcohols to aldehydes and carboxylic acids, but in order to get a reasonable price, I had to order 100g ($147 shipped). I don't need all of that, so if anyone is interested, I'd be happy to share at cost, buyer pays shipping. This is a fascinating catalyst, and I'm super excited to try it out and see what other members can come up with using it.

Sidmadra - 19-3-2018 at 13:12

Are you ordering it from China? If so that price seems 10x too high. Tempo is a common item so you should be able to get it $200-300/kg from China. Figure that if you're going to sell what you have leftover, you may as well get a good deal?

If you do end up getting some, I may be interest in grabbing some later on.

weilawei - 19-3-2018 at 14:27

I'm getting it from a US supplier. I have no experience with negotiating custom orders from China. My experience with products from there is limited to ordering off eBay. I've already placed the order (otherwise I'd look into ordering it from China) and received confirmation--I should have it within the week.

As I said, I'm just looking to get rid of the excess, not to make anything off of it. Small amounts, larger amounts, today, tomorrow, or far in the future--that's all fine by me. I'm in no rush. (It was bonus money from work anyway, so I treated myself.) What would be really cool is if we got a bunch of people to try out different reactions with it and report on it.

Myself, I'm going to start simply with TEMPO/TCCA mediated oxidation of ethanol to ethanoic acid. I've got a small stack of papers here with all sorts of neat reactions.

Sidmadra - 19-3-2018 at 14:49

Ahhh I see. About the TEMPO/TCCA reaction, isn't TCCA able to oxidize all the way to carboxylic acid on its own? I seem to remember TCCA being a pretty potent oxidizer. I remember wanting to make acetaldehyde from ethanol and TCCA but never did because it would go all the way to the acid, or so I thought.

weilawei - 19-3-2018 at 17:03

From "Trichloroisocyanuric/TEMPO Oxidation of Alcohols under Mild Conditions: A Close Investigation" by De Luca, et al.:

Quote:
To clarify some mechanistic aspects of the oxidation, we have conducted some additional runs. The course of the oxidation does not change using catalytic alkaline salts (NaBr, NaI, LiF) other than NaCl or using Bu4NBr. The use of only 1 equiv of TCCA causes a very slow reaction: in the case of oxidation of benzyl alcohol, the reaction requires 15 h at 25 °C for completion. The reaction is very slow even when NCS (2 equiv) is used instead of TCCA. The oxidation to carboxylic acid does not occur in the absence of water in the reaction mixture, and the reaction stops with the formation of the aldehyde. The reaction can be conducted both in acetone and MeCN, under the reported experimental conditions, with the same identical results, while only carbonyl compounds are formed using dry dichloromethane.11 Increasing the amount of water increased the formation of chlorinated products; under these conditions, benzyl alcohol is oxidized slowly to a mixture of chlorosubstituted benzoic acids.

It is noteworthy that the oxidation of the intermediate aldehyde does not require TEMPO as catalyst. In fact, the aldehyde is rapidly oxidized to the corresponding carboxylic acid by treatment with 1 equiv of TCCA in acetone/water, without addition of the catalyst.


Quote:
(22) The hydrolysis of TCCA seems to be catalyzed by the presence of even catalytic amounts of halide ions; in the absence of traces of sodium halides, no oxidation to carboxylic acids takes place.


It looks like with TEMPO that you can select for either the aldehyde or the carboxylic acid by various parameters: temperature, reaction time, choice of stoichiometric oxidant, use of phase transfer catalysts, etc..

Quote:
In 1987, Anelli et al. made a key contribution to TEMPO-mediated oxidations by showing that the very cheap reagent chlorine bleach (aqueous NaOCl) can function very effectively as a stoichiometric oxidant for alcohols in the presence of traces of 4-MeO-TEMPO. 3 They established a protocol involving a reaction run at 0 C in a biphasic CH2Cl2–water mixture in the presence of excess of NaOCl, NaHCO3, KBr, and catalytic 4-MeO-TEMPO for oxidation to aldehydes. Under these conditions the oxidation to acids is quite slow. If the acid is desired, it is advisable to add a phase-transfer catalyst to speed up the oxidation.


[Edited on 20-3-2018 by weilawei]

JJay - 19-3-2018 at 17:28

I am interested in some TEMPO. I sent you a U2U.

Melgar - 21-3-2018 at 17:50

I have a bunch of excess elemental selenium and TBAB, among other things. I'm really not in much of a position to be doing chemistry (or even talking about chemistry, really :P) but that's been one of the ones I've been trying to get my hands on for a while, without much success. I'd prefer to trade something I have since I'm pretty much broke, but could possibly purchase a small amount.

I'd even trade one of my more expensive reagents like LiAlH4, PdCl2, AgNO3.

weilawei - 22-3-2018 at 05:08

Well, bad news is that fell through. I got a notice that it was no longer available, and my order was refunded. The search continues! I didn't want to have to synthesize it, but that's looking like my best option. There is an old post around here with details, though.

JJay - 22-3-2018 at 08:38

I was thinking about trying... Metacelsus made some: https://www.sciencemadness.org/whisper/viewthread.php?tid=62...