TEMPO

Description

2,2,6,6-Tetramethylpiperidine is a product that is used for the most diverse purposes because of its strong basicity, for example, as a light stabilizer for polyolefins, as a cocatalyst in olefin polymerizations (Ziegler catalysts), as a building block for the synthesis of pharmaceuticals and crop protection products, as a cocatalyst in the synthesis of dichloroacetyl chloride. The 4-unsubstituted 2.2.6,6-tetramethylpiperidine is generally prepared from the corresponding 4-oxo compound. It is known that triacetonamine can be converted by hydrazine to the hydrazone, which is then cleaved in the presence of alkali into 2,26,6-tetramethylpiperidine and nitrogen.

Chemical Properties

orange crystals or powder

Characteristics

2,2,6,6-Tetramethylpiperidinooxy(TEMPO) has the characteristics of high yield, good selectivity, good stability, and recyclable use.

Uses

TEMPO(2,2,6,6-Tetramethylpiperidinooxy) is a stable radical prepared through the oxidation of 2,2,6,6-tetramethylpiperidine. TEMPO has a wide range of applications including use as a free radical scavenger, a reagent in organic synthe sis and as a structural probe in electron spin resonance spectroscopy. TEMPO can also be used as a mediator in free radical polymerization.

Uses

In organic chemistry as a radical trap, 2,2,6,6-Tetramethylpiperidinooxy can be used as a catalyst and in polymerization mediation.

Uses

TEMPO can be used:

• As a catalytic oxidant for copper-catalyzed, greener oxidation of alcohols under aerobic conditions.
• As a catalytic oxidant in the iodobenzene diacetae oxidation of nerol to neral.
• For trapping the styrenyl radical generated from benzoyl peroxide during nitroxide-mediated radical polymerization of styrene.
• In the carboxylation of water-resistant nanofibrillated cellulose (NFC) films.

Reactions

TEMPO derivatives are widely used as two-electron redox mediators for selective oxidation of various organic substrates. The oxoammonium form of TEMPO contains an electrophilic nitrogen atom, to which different nucleophiles such as alcohols or amines can attach. While the substrate contains an alpha-hydrogen atom, the subsequent proton shift and oxidative elimination of the TEMPO in hydroxylamine form may occur, which results in a formal 1,2-dehydrogenation of the substrate. The catalytic cycle can then be closed by two-electron oxidation of the hydroxylamine form to oxoammonium form using chemical oxidants^[1].

General Description

For a synthetic protocol using NMP initiators, contributed by Prof. Karen Wooley, please visit our technology spotlight.

reaction suitability

reagent type: oxidant

Synthesis

(1) Take an appropriate amount of 2.2.6.6-tetramethylpiperidine, add catalyst and methanol and mix well, and the mass:mass:volume ratio of 2.2.6.6-tetramethylpiperidine to catalyst and methanol is (8 to 10):2:3;
(2) heat the mixture to 50 to 70C (preferably 50-60C), and dropwise add hydrogen peroxide to the reaction, and the dropwise addition amount of hydrogen peroxide is 2.2. 6.6-tetramethylpiperidine 6 to 7 times;
(3) the solution at the end of the reaction is filtered, the filtrate is extracted with propyl acetate, the propyl acetate phase is distilled to remove propyl acetate, and then cooled down and centrifuged to obtain 2,2,6,6-tetramethylpiperidine oxide.

Purification Methods

Purify TEMPO by sublimation (33o, water aspirator) [Hay & Fincke J Am Chem Soc 109 8012 1987, Keana Chem Rev 78 37 1978].

References

[1] Vereshchagin, A., Kalnin, A. Y., Volkov, A., Lukyanov, D., Levin, O. (2022). Key Features of TEMPO-Containing Polymers for Energy Storage and Catalytic Systems. Energies. https://doi.org/10.3390/en15072699