4-Hydroxy-2,2,6,6-tetramethyl-piperidinooxy
[CAS# 2226-96-2]

Identification

• Classification: Analytical chemistry >> Standard >> Spectrometric standard
• Name: 4-Hydroxy-2,2,6,6-tetramethyl-piperidinooxy
• Synonyms: 2,2,6,6-Tetramethyl freeagaoxy-4-piperidyl; 4-Hydroxy-TEMPO free radical
• Molecular Formula: C₉H₁₈NO₂
• Molecular Weight: 172.25
• CAS Registry Number: 2226-96-2
• EC Number: 218-760-9
• SMILES: CC1(CC(CC(N1[O])(C)C)O)C

Properties

• Melting point: 69-73 °C
• Water solubility: soluble

Safety Data

• Hazard Symbols: Xn
• Risk Statements: R22;R36/38
• Safety Statements: S26;S37/39

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312

Discovery and Applications

4-Hydroxy-2,2,6,6-tetramethyl-piperidinooxy, or TEMPO-H, a derivative of TEMPO, was synthesized as part of ongoing research into stable free radicals in the late 20th century. Chemists aimed to modify TEMPO's structure to enhance its solubility and reactivity in specific applications. The addition of a hydroxyl group at the 4-position of the piperidine ring resulted in TEMPO-H, a compound with unique properties that expanded its potential uses in various fields.

Like TEMPO, TEMPO-H serves as an efficient catalyst for oxidation reactions, particularly in organic synthesis. Its hydroxyl group enhances solubility in polar solvents, making it suitable for reactions requiring aqueous or protic conditions.

TEMPO-H finds extensive use in radical polymerization reactions, facilitating the synthesis of functional polymers with controlled structures and properties. Its hydroxyl group enables facile modification of polymer chains through post-polymerization functionalization, enhancing versatility in material design.

The hydroxyl group in TEMPO-H enhances its antioxidant properties compared to TEMPO, making it a potent scavenger of free radicals.

TEMPO-H-modified electrodes are utilized in electrochemical sensors for detecting analytes with high sensitivity and selectivity. Its hydroxyl group can facilitate specific interactions with target molecules, improving sensor performance in various applications, including environmental monitoring and healthcare diagnostics.

TEMPO-H serves as a food additive for preserving the quality and shelf life of packaged foods by inhibiting lipid oxidation. Its hydroxyl functionality enhances solubility in food matrices, allowing for effective antioxidant activity without affecting taste or texture.

TEMPO-H is incorporated into skincare formulations for its antioxidant properties, offering protection against oxidative damage and promoting skin health. Its hydroxyl group enhances penetration into the skin, ensuring efficient delivery of active ingredients.

References

2003. Kinetics and Mechanism of the Reaction of a Nitroxide Radical (Tempol) With a Phenolic Antioxidant. Free Radical Research, 37(1).
DOI: 10.1080/1071576031000081587

2024. [Contractive function of mesenteric lymph nodes in obese rats]. Voprosy Pitaniia, 93(4).
DOI: 10.33029/0042-8833-2024-93-4

2010. Scavenging Free Radicals To Preserve Enhancement and Extend Relaxation Times in NMR using Dynamic Nuclear Polarization. Angewandte Chemie International Edition, 49(32).
DOI: 10.1002/anie.201000934