4-Hydroxy-TEMPO (CAS 2226-96-2), also known as Tempol, is a stable nitroxyl radical supplied as an orange crystalline solid or crystalline powder, serving as a polymerization inhibitor and regulator in acrylic and styrenic systems, a catalyst in selective oxidations, and a reagent in pharmaceutical research. It is widely used in chemical manufacturing and research environments where controlled radical activity and oxidation stability are required. The material offers reliable handling characteristics and long shelf life under proper storage conditions.
Typical Properties
| Molecular formula | C9H18NO2 |
|---|---|
| Molecular weight | 172.24 g/mol |
| Appearance | solid |
| Form | Crystals or Crystalline Powder |
| Color | Orange |
| Melting point | 71-73 °C |
| Water solubility | soluble |
| Flash point | 146°(295°F) |
| pH | 8.2 (20g/l, H2O, 20°C) |
| GHS signal word | Danger · Corrosive, Irritant / harmful, Health hazard |
| HS code | 29333999 |
Typical literature values for identification; lot-specific results are stated on the certificate of analysis (COA) and the safety data sheet (SDS) that accompany every delivery.
4-Hydroxy-TEMPO
Applications
Used as a polymerisation inhibitor and regulator in acrylics, styrenics and other radical based polymer systems. Applied as a catalyst or mediator in selective oxidation reactions. Utilised in fine chemical synthesis, pharmaceutical research and laboratory applications. Also used as a reference compound in analytical chemistry and electrochemical studies where radical stability is essential.
Safety & Risks
Irritant to skin, eyes and respiratory system. Avoid inhalation of dust and prolonged contact. Handle with appropriate PPE and adequate ventilation. Stable under normal conditions but should be kept away from strong reducing agents.
Packaging
Supplied in 1 kilogram, 5 kilogram or 25 kilogram HDPE containers or fibre drums with inner liners. Store in a cool and dry place protected from light in accordance with SDS recommendations.