TEMPO catalyst: what makes CAS 2564-83-2 useful, and what to check before you buy it

In short

• TEMPO is 2,2,6,6-tetramethylpiperidine-1-oxyl, a stable nitroxyl radical identified by CAS 2564-83-2 and EC 219-888-8.
• Its main value in synthesis is selective oxidation, especially the conversion of alcohols to aldehydes or ketones under controlled conditions.
• TEMPO is normally discussed as a catalyst, but the real reaction system also depends on the co-oxidant, solvent, pH, temperature and substrate.
• For purchasing, the important checks are identity, assay, impurity profile, COA, SDS, packaging and lot traceability.
• A supplier page should not promise a universal yield or a universal procedure. TEMPO is a tool, and its performance belongs to the specific reaction.

TEMPO is one of the better-known stable organic radicals in fine chemical synthesis. That sentence sounds unusual because radicals are usually treated as short-lived intermediates, not as products a buyer orders by the drum or bottle. TEMPO is different: the nitroxyl radical is stabilised by the crowded piperidine ring, so the material can be isolated, stored and used deliberately.

That stability is the reason TEMPO (CAS 2564-83-2) appears in both laboratory procedures and industrial route development. It is not chosen because it is exotic. It is chosen because it gives process chemists a controlled way to move electrons in oxidation chemistry without treating every alcohol, aldehyde and ketone in the same way.

Chemical identity

For procurement and regulatory review, start with identifiers rather than trade names. TEMPO is a short name, and short names travel badly across documents, languages and supplier catalogues.

The phrase "stable radical" is the key. The unpaired electron is on the nitroxyl group, and the four methyl groups around the piperidine ring give steric protection. That does not make the material inert. It means the radical is persistent enough to be used as a reagent or catalyst component rather than existing only as a fleeting intermediate.

Why TEMPO works in selective oxidation

The most common reason to specify TEMPO is selective oxidation of alcohols. In practical terms, it helps a chemist convert a primary alcohol toward an aldehyde, or a secondary alcohol toward a ketone, without applying a harsher oxidation system than the substrate can tolerate.

TEMPO does not work alone in most useful preparations. It cycles between nitroxyl and oxoammonium forms, while another oxidant regenerates the active species. That co-oxidant can be chosen from several systems, and that choice is not a detail. It changes pH, salt load, waste profile, metal content, temperature window and functional-group tolerance.

That is why a serious TEMPO page should avoid a universal recipe. A procedure that is mild for one substrate can over-oxidise another. A system that is attractive at bench scale can become awkward at plant scale because of chlorinated waste, metal removal, heat release or quench behaviour.

Where TEMPO is used

Pharmaceutical intermediates. TEMPO-mediated oxidation is useful when a route needs aldehydes, ketones or acid derivatives from alcohol-containing intermediates, especially when other functional groups are present and selectivity matters.

Fine chemicals and agrochemical intermediates. Many fine chemical routes value clean functional-group interconversion more than maximum reagent strength. TEMPO belongs in that category: it is often selected when the oxidation step must be controlled rather than simply forced.

Flavour and fragrance chemistry. Alcohol-to-aldehyde and alcohol-to-ketone transformations are common in aroma chemistry. TEMPO systems can be evaluated where substrate sensitivity and odour-active impurity control matter.

Polymer and radical chemistry. TEMPO and related nitroxides are also used in radical chemistry, including nitroxide-mediated processes and as radical scavengers or probes. That is a different use case from alcohol oxidation, but it comes from the same stable-radical identity.

What TEMPO does not tell you by itself

A CAS number confirms identity. It does not tell you whether a lot is suitable for your process.

Assay matters, but impurities matter too. For a catalytic or near-catalytic material, a small amount of the wrong impurity can matter more than a small change in headline purity. Ask how assay is measured and whether the certificate reports named impurities or only total purity.

Colour and appearance can be process signals. TEMPO is commonly described as a red to orange crystalline material. Appearance is not a substitute for analysis, but a lot that looks different from previous deliveries deserves investigation before it enters a validated or scale-up process.

Particle form affects handling. A powder or crystalline solid that assays correctly can still behave differently in charging, dissolution or dust control. If the material is going into a plant process, physical form belongs in the discussion.

The reaction system decides performance. TEMPO loading, co-oxidant, solvent, pH and temperature are process variables. A supplier can provide material documentation; the buyer's process team still owns the route decision.

Handling, storage and safety

TEMPO is an industrial chemical and should be handled according to the safety data sheet for the specific grade and package being purchased. Public supplier SDS examples commonly classify TEMPO-containing products as corrosive or damaging to eyes and hazardous to the aquatic environment, but the legally relevant document is the SDS supplied with the lot.

For practical handling, buyers should check:

1. The latest SDS for the exact product and grade.
2. Required eye, skin and respiratory protection for the operation.
3. Storage compatibility with oxidants, acids, bases and other site chemicals.
4. Whether the package size and closure suit the way the plant will charge the material.
5. Local requirements for labelling, waste routing and transport.

Do not rely on a blog post for safety classification. Use the SDS, the label and local regulation.

How to qualify a TEMPO supplier

For a research order, price and availability may be enough. For pilot or production use, the supplier question becomes more specific.

Confirm the identifiers. Purchase documents should include TEMPO, CAS 2564-83-2 and the systematic name. This reduces the chance of a short-name mismatch.

Ask for the COA before scale-up. The certificate should report lot number, assay method, result, date and the specification limits that result is judged against.

Ask for the SDS before shipping. The SDS decides labelling, storage and transport preparation. A quote without an SDS is not enough for import or site approval.

Check batch traceability. If a process behaves differently, the lot number is what lets the supplier investigate whether the difference is analytical, physical or logistical.

Discuss packaging early. A sample bottle and a production package solve different problems. The correct package is the one the site can receive, store, open, dose and reseal without creating unnecessary exposure.

Frequently asked questions

Source TEMPO from Palica Chem

Palica Chem supplies TEMPO (CAS 2564-83-2) for fine chemical, pharmaceutical intermediate and research applications. Contact us for current specification, COA, SDS, packaging options and quotation.

Related

• TEMPO product page - CAS 2564-83-2, EC 219-888-8 and inquiry form
• 4-tert-Butylcatechol (TBC) - polymerisation inhibitor and stabiliser
• Ammonium persulfate (APS) - radical initiator for polymerisation

Sources. The identifiers, formula and molecular weight above are checked against PubChem's TEMPO entry and the TEMPO product page on this site. The safety discussion is intentionally general and points back to the SDS for the purchased grade; public supplier SDS pages classify TEMPO products with serious eye or corrosive hazard language, but the buyer's document of record is always the SDS supplied for the exact lot and jurisdiction.