Chemistry sometimes feels like a field that reinvents itself every decade. In the late 1950s, a spark of creativity led to the development of stable nitroxyl radicals. Among these, 2,2,6,6-Tetramethyl-4-Oxopiperidinooxy, better known as TEMPONE, moved research forward. The introduction of this particular compound allowed chemists to investigate radicals with a level of control that earlier generations could only imagine. Researchers started blending classic organic synthesis with radical chemistry, and TEMPONE turned into a dependable workhorse both in academic labs and industry. Voices in the field credit the sturdy nature of TEMPONE’s structure as the reason students now train using this radical in spins and electron transfer experiments. Not everyone in those early days believed a stable radical could last on the shelf, but TEMPONE did.
This compound sits as a crystalline or powdery substance, known for its robust ESR (electron spin resonance) signal. Technicians and students recognize its deep red hue almost immediately. Sometimes TEMPONE comes pre-packed in light-blocked vials; suppliers from North America, Europe, and East Asia all sell it under several different labels. Often, the material carries a purity certificate, reflecting the reality that even minor impurities can change the outcome of a sensitive radical experiment. On the open market, TEMPONE stands alongside TEMPO and its close variants—but its carbonyl group offers more chemistry per gram.
At room temperature, TEMPONE stays solid, rarely absorbing much moisture from the air. Its melting point hovers around 70-75°C, and it dissolves easily in most organic solvents—especially acetone, chloroform, and methanol. The nitroxyl group defines its radical character, so TEMPONE always gives a sharp ESR signature. The steric bulk of the four methyl groups provides the shielding that lets the radical live so long outside the fume hood. In practice, chemists prefer TEMPONE for experiments requiring a detectable ESR signal in biologically relevant environments, since the compound doesn’t react instantly with typical cell components.
Suppliers note the content as 2,2,6,6-Tetramethylpiperidin-4-one-1-oxyl, usually delivering it at 97% or higher purity. The CAS number helps track regulatory issues—usually noted as 3317-34-6. Labels warn about potential reactivity and require gloves and goggles for any handling. Labs wanting repeatable signals often choose HPLC-grade variants for demanding applications. Documentation outpaces some older organic materials, with technical datasheets describing solubility, storage temperature, sensitivity to light, and disposal considerations.
Chemists usually begin with 2,2,6,6-Tetramethylpiperidine, oxidizing it at the four-position to introduce a carbonyl, and further oxidizing the nitrogen to make the nitroxyl radical. Common oxidants are bleach (sodium hypochlorite) or m-CPBA, often with careful pH control to avoid overoxidation or violent decomposition. The method delivers a crystalline product after extraction and drying, usually monitored with TLC, ESR, or NMR. Some bench chemists prefer small-batch syntheses for student labs, quoting safety and freshness, while commercial producers use larger reactors and chemical engineering controls to keep the process stable and the material reproducible.
TEMPONE reacts less aggressively than unshielded radicals. Its main utility rests in its ability to undergo redox cycling—switching between radical and non-radical forms. Adding reducing agents like ascorbic acid quenches the radical; oxidizers restore it. The piperidone moiety opens up further derivatizations—think hydrazone formation, oxime syntheses, or even polymer-bound versions for more specialized catalysis. Researchers graft TEMPONE onto silica supports, trigger ring substitutions, or blend it into polymer films for analytical chemistry. The structure resists acidic and basic hydrolysis far longer than most radicals, so TEMPONE survives in strange places—blood serum, industrial reactors, even some environmental remediation tests.
Chemists use several names for the same material: 4-Oxo-TEMPO, TEMPONE, and Tetramethylpiperidone nitroxide all describe the same radical. Catalogs sell it as 2,2,6,6-Tetramethyl-4-piperidone-1-oxyl or just 4-Oxo-TEMPO. Some literature mixes in the shorthand “TMPOX” or “4-keto-TEMPO,” but the ESR spectrum usually settles the argument for anyone unsure of the identity. Even journal abbreviations sometimes swap in alternative names, making thorough database searching a chore. In the real world, experienced researchers learn to recognize the structure at a glance, regardless of the label on the jar.
Working with TEMPONE, the safety issues seem manageable, largely because the compound refuses to react with air or water under most conditions. Still, the radical’s potential to trigger redox chemistry demands respect: gloves, goggles, and lab coats form the usual armor. Material safety data sheets urge technicians to avoid skin contact or inhalation, since small molecules sometimes cross biological barriers unnoticed. Safe storage in amber bottles prevents light-driven degradation. Disposal follows standard procedures for organics, and local regulations dictate limits for drain disposal or incineration. Spills rarely spark fires, but even a small amount landing on the wrong surface may stain or interfere with other sensitive lab processes.
TEMPONE shows up all over, from biophysical chemistry to industrial processing. In EPR spectroscopy, it acts as a reference standard, helping scientists map local environments or the presence of oxygen in blood or polymer films. Medical researchers value TEMPONE as a probe for oxidative stress, dosing animals or cells and measuring decay products to decipher how organisms age or respond to toxins. It helps in controlled polymerization projects as an inhibitor and chain transfer agent, making it easier to dial in the weight distribution of plastics. Analytical labs use it to map microenvironments in aqueous or lipid phases, leveraging its unique signal. In my experience, environmental labs also deploy TEMPONE to test the persistence of free radicals in contaminated soil or water, simulating what happens as industrial waste breaks down in the real world.
Ongoing studies keep branching in new directions. One dynamic trend traces how TEMPONE derivatives map into biological membranes—where paramagnetic labels can highlight cell boundaries or reveal hidden oxidative processes. Diagnostics companies invest in spin-trapping reagents built from the same piperidone core, tweaking the structure for selectivity or signal strength. Computational chemists run simulations, investigating the radical’s interactions with proteins or polymers. In catalysis, engineers experiment with surface-immobilized TEMPONE, aiming for recyclable oxidation catalysts that avoid precious metals. Some research labs swap in heavy isotopes of nitrogen for specialized EPR labeling—a trick that lets them distinguish subtle differences in signal amid noisy biological samples.
TEMPONE generally rates as less hazardous than most free radicals, but research shows it can interact with certain cellular targets, depending on dose and exposure route. Animal studies reveal mild toxicity on repeated exposure, especially at doses much higher than those used in analytical chemistry. The compound doesn't linger long in biological tissues, with kidneys taking care of elimination. Some older safety studies hint at liver stress in rodents dosed for weeks, but most published work supports brief, low-level handling as reasonably safe in a controlled lab. Students learn not to underestimate radicals, even if TEMPONE’s record looks pretty clean compared to other nitroxides on the market.
Looking ahead, chemists keep finding new applications. Redox-active materials based on TEMPONE derivatives promise to help buffer high-performance batteries or aid in water purification. Biologists continue probing the radical’s potential as a targeted therapeutic for conditions tied to oxidative stress. Diagnostic imaging groups push to fine-tune TEMPONE’s signal for noninvasive scans, hoping one day to track disease progression using safe doses in humans. Synthetic chemists reinvent catalysts using TEMPONE cores for greener oxidations, swapping out toxic metals for these resilient organic mediators. If the past sixty years offer lessons, it's that flexible molecules with dependable reactivity rarely fade from the research spotlight—they find new jobs, new questions to answer, and new properties waiting for someone to tinker and discover.
Walk into a working chemistry lab, and you will probably spot bottles labeled with long, intimidating names. Among them, 2,2,6,6-Tetramethyl-4-Oxopiperidinooxy—often just called TEMPO—keeps showing up for good reason. Chemists rely on TEMPO because it simplifies a process that can otherwise get painfully tricky: controlling oxidation. In the world of organic chemistry, oxidizing one molecule without tearing apart another takes finesse, and TEMPO brings that skill to the table.
TEMPO turns selective oxidation from an uphill grind to a routine step. It’s called a radical, which really just means it holds an unpaired electron that can reshape other molecules in controlled ways. If you need to turn an alcohol group into an aldehyde or a ketone, standard oxidizers can go too far, destroying fragile parts of your molecule. With TEMPO, reactions stay on a predictable path. That reliability saves money and cuts waste—a win for both labs and production lines.
During my graduate research, TEMPO earned a loyal spot on the bench for these very reasons. Other compounds would scorch what I was working with, blowing out side products and lowering the yield. Simple swapping in TEMPO made difficult steps almost boring—in the best way. Major pharmaceutical plants value the same advantage. Scaling up requires processes that work the same every single batch, and this nitroxyl radical stands up to that demand.
Pharmacy giants and academic labs both keep exploring how TEMPO can fit into greener chemistry. Many traditional oxidizers generate harsh waste. TEMPO partners with mild co-oxidants and works at room temperature, trimming costs and environmental headaches. That’s where regulatory groups start to pay attention—lower hazards mean fewer headaches during waste treatment or worker exposure monitoring.
Interest in biomedical research has also grown. TEMPO’s unique structure lets it interact with free radicals in the human body, which play a role in aging, cancer, and brain disease. Scientists use it as a probe to expose pathways involved in oxidative stress. The health implications haven’t reached the stage of daily treatment, but diagnostic uses keep surfacing in peer-reviewed journals, hinting at a wider future role.
Innovation often runs faster than safety regulations, so responsible handling of compounds like TEMPO matters. Chemical suppliers now publish clear handling guidelines. They stress its stability at room temperatures and caution against mixing it with strong acids or bases. When I started, working with new chemicals brought a bit of guesswork, but improved labeling and digital Safety Data Sheets have raised the bar for safe use.
Success in using specialized reagents also comes down to straightforward training. Universities have ramped up hands-on workshops, focusing on reaction setup, waste disposal, and emergency response. These investments pay off. Serious incidents drop, and more students can tackle ambitious experiments without fear.
Using compounds like TEMPO with care and intention points the field toward more sustainable chemistry. Researchers and manufacturers alike hold responsibility to keep looking for smarter ways to solve persistent problems. The next breakthrough could come from unexpected places—or from taking a tried-and-true tool and using it just a little differently.
2,2,6,6-Tetramethyl-4-Oxopiperidinooxy, known as TEMPO to most chemists, pops up all over the place in organic labs. It's famous for how well it helps push along oxidation reactions, especially those that avoid heavy metals. That reputation as a reliable helper usually gives newcomers the impression that it’s harmless. That’s misleading.
Read through the safety data sheets, and the story shifts. TEMPO is an irritant. Skin and eyes react quickly after contact — redness, itching, in some cases, damage that needs medical follow-up. Breathing in dust or vapor sets off coughing and might trigger asthma in people who have never shown symptoms before. I worked with a chemist who once forgot his gloves for a single pipetting step. The rash and peeling skin that followed became the cautionary tale for the rest of us in the lab. No immediate hospital visit, but weeks of discomfort.
TEMPO itself can catch fire more easily than most expect. It reacts strongly with oxidizers and acids. I remember one fire drill that turned real within seconds after TEMPO residue mixed with nitric acid waste in a poorly labeled container. Emergency protocols and fire extinguishers kept everything under control, but that smell stuck around for days. Regular lab safety training exists for a reason — and TEMPO belongs on the list of compounds that don’t take shortcuts with labeling, storage, or waste management.
Chronic data lag behind acute effects because most TEMPO work uses small quantities. That does not equal “safe in the long run.” Skin allergies develop slowly, and repeated dust inhalation is thought to do harm that adds up. Everyone in research knows that new chemicals show new risks over time. Just because nothing showed up ten years ago doesn’t mean no one’s at risk.
Lab gloves and goggles feel like a hassle until skin begins to burn — these habits don’t just check a box for safety officers. Fume hoods never go out of style because even low volatility couldn’t keep vapors or dust from hanging in still air. A good lab coat, regular glove changes, and spending a minute to double-check storage containers lower risk more than any after-the-fact measure. Chemical safety training makes a real difference: everyone on site gets briefed before they touch new reagents. This shifts “handling with care” from an abstract rule to a routine that everyone takes seriously.
I see a pattern — people get used to chemicals that never caused trouble until procedures changed or the workload ramped up. TEMPO keeps its dangers low when handled by folks paying attention and respecting health and fire risks. Shortcuts with personal protective equipment or waste disposal just send people to the ER or set alarm bells ringing. If the idea of working with it seems intimidating, that means the right approach is already in mind: handle with care, double up on labeling, and treat every contact as potentially risky.
Safe handling of TEMPO calls for more than just equipment; it needs a mindset that puts health first and recognizes danger early. Chemical work draws plenty of people who thrive under pressure, but pushing through without respect for hazard signals turns a useful tool into a serious threat. Respect, preparation, and focus keep work efficient — and let tomorrow’s research move forward with everyone intact.
Every lab worker has stared at the bright, orange-red crystals of 2,2,6,6-Tetramethyl-4-Oxopiperidinooxy—usually called TEMPO—and wondered just how forgiving they are. With so many mishaps coming from the storeroom, especially when the weather changes or power gets spotty, storage isn’t just an afterthought. The air oxidizes everything, the humidity wrecks labels, and poor housekeeping can turn a safe place into a ticking hazard. A story comes to mind: in my very first week as a grad student, the housekeeping manager found a package of TEMPO sitting open, surrounded by dissolved plastic caps. Better habits avoid those headaches.
TEMPO shows off its stability in the lab, but even tough molecules have their breaking points. Temperatures above room-level chip away at its shelf life. For best results, storage should mean a spot around 20°C—no sunbeams, no heat vents, nothing fancy. Humidity invites clumping and, over time, chemists report more decomposition when the air gets sticky. In the Southeast, for example, you’ll find scientists double-bagging the jars and adding a silica packet to every bottle. If humidity creeps in, that brick-red solid may darken or become tacky, which means quality has started slipping.
Long-term, darkness matters. Light can prompt radical side-reactions—ironic for a radical scavenger like TEMPO. Ultraviolet light actually spurs loss of function, so amber bottles or an opaque storage box block any light leaks, even with the lights off. Tossing all these together, storage looks like a low shelf away from windows, in a closed cabinet, with every cap screwed tight and every label legible.
Chemical incompatibility sparks dangerous situations. TEMPO’s odd structure includes a nitroxide group, and those tend to react with acids and peroxides. That famous 2018 incident at a small organic chemistry lab—inattentive storage of TEMPO beside concentrated hydrochloric acid—caused a slow, undetected reaction. It didn’t end in an explosion, but the rearranged products smelled awful, and the cost of replacing ruined supplies stretched the department’s patience. Segregating TEMPO away from acids, peroxides, strong oxidants, and reducing agents avoids this entire category of blunder. If acids land in one cabinet and oxidizers in another, accidents shrink.
Good labeling and tracking shape a safe workspace. Hand-labeling the open date, noting down the last check, and rotating inventory builds trust among colleagues. Expiry dates help, but real life means opening bottles, using some, and coming back months later, so clear communication on containers is key. Waste TEMPO responsibly: after the project wraps up, collecting leftovers in a secure, clearly marked waste bottle keeps the next person from using something off-spec.
The science doesn’t work unless the storage does. I have seen research lost to lazy storage, and I’ve seen libraries hum with smooth, safe workflow. TEMPO isn’t tricky if you just treat it with care, and the lessons from one compound ripple out to everything in the chemical storeroom.
Years of working in research labs have taught me this: even tiny differences in chemical purity can shake an experiment’s outcome—or wreck it. 2,2,6,6-Tetramethyl-4-Oxopiperidinooxy, or more simply, TEMPO, stands as a favorite in organic chemistry and polymer science. Its reputation as a powerful oxidizing agent hangs on one big hook: the purity level in the bottle.
Impurities are like potholes on an otherwise smooth road. Most commercial suppliers push TEMPO at purity levels of 97% or greater. In fact, high-performance labs will often shell out for 98% or above. Even a one-percent difference pushes the limits of what a reaction can tolerate, sometimes nudging sensitive syntheses off the rails.
Working with TEMPO at different purity grades gives you quick feedback. Lower purity often brings inconsistent batch results, extra troubleshooting, and extra purification steps. Manufacturers love to tout 99%+ “HPLC pure”—not just for show, but because real-world chemists demand consistency. Even that last 1% of unknowns sometimes leeches into downstream reactions as unexpected byproducts.
It’s not just about academic pursuits. Pharmaceutical work and regulatory filings lean hard on traceable, ultra-pure reagents. If there’s a contaminant in that last percent, that could spell disaster at scale or trigger weeks of review for a new chemical entity filed with the FDA.
I’ve learned to ask for certificates of analysis (CoAs). It’s tempting to trust the purity printed on a bottle’s label, but CoAs break things down: they show which impurities slip by during synthesis and packaging. With TEMPO, side products like piperidine derivatives or residual solvents often pop up. Skipping the CoA risks sinking a week’s work if a rogue impurity shows up in the NMR spectrum instead of your expected product.
Batch-to-batch consistency also matters more than folks think. Stocking up with a single lot number avoids surprises. Labs buying one-off grams from inconsistent suppliers sometimes watch yields drop for reasons they don’t spot at first.
Trusting catalogs only goes so far. We use TLC, GC-MS, and sometimes melting point checks before using a new bottle in a critical sequence. These simple tests often highlight problems early. I remember an undergraduate thesis project grinding to a halt just because a bad lot of TEMPO routinely failed to oxidize an alcohol. Only later did we realize an impurity scavenged the active species. If QC had caught that on day one, a month of frustration would have disappeared.
For serious work, analytical testing means everything. Anyone who’s run control reactions knows clean reactants make for clean results—and credible data you can actually publish.
Better supply chains mean standards. That takes investing in reputable suppliers who stay transparent about their quality systems. It takes persistent record-keeping and skepticism, even if the bottle says “99% pure.” Sometimes, making TEMPO ultra-pure in-house works out better than gambling on a bargain batch from an unknown source. Stronger communication between buyers and suppliers helps everyone: sending back lots with trace impurities usually brings better material next time.
At the end of the day, purity drives progress. Whether in academia or industry, clear communication and stubborn attention to detail keep experiments moving and discoveries coming.
2,2,6,6-Tetramethyl-4-oxopiperidinooxy, often known as TEMPO, draws attention for its usefulness in labs and manufacturing. It unlocks complicated chemical reactions, creates polymers, and helps in oxidative processes. Unlike spilled vinegar or dirt tracked into a hallway, TEMPO brings risks that echo through both health and ecosystems. Handle it the wrong way, and a slip-up can last longer than a workday.
Chemical exposure rarely wears name tags. Breathing in or touching TEMPO can lead to irritation, headaches, or worse. Its bright appearance doesn’t warn you about its toxic punch to aquatic life. Those who pour leftovers into the sink, hoping water treatment will clean it all up, miss the impact this chemical creates downstream. Fish and other organisms in rivers can’t process these man-made molecules.
It's tempting to view disposal as someone else’s job. That approach has filled landfills with dangerous waste, fouled water systems, and left future generations to pick up after us. Growing up in a community where runoff from old industrial sites hurt crops and left people worried about drinking well water, I can’t forget how much damage can hide beneath the surface.
Regulations don’t sit around for decoration. They show the hard lessons learned after accidents, poisonings, and legal fights. In the U.S., the Environmental Protection Agency outlines rules in the Resource Conservation and Recovery Act (RCRA). TEMPO may not land on every restricted list, but its characteristics place it squarely in the zone of “treat with respect.” Facilities with professionals on staff often turn to high-temperature incineration. Not just tossing something into a fire, but using controlled, licensed services so no gases or residues escape.
For folks working in smaller labs or even university classes, the answer isn’t set by how little you have on hand. Keep the chemical in tightly sealed, clearly labeled containers. No shortcuts using general waste bins or pouring it down a drain. If questions flare up about which method fits, local hazardous waste coordinators offer real guidance.
Waste collection days in cities or academic campuses connect individuals with professionals who track every ounce and use approved methods. Most will ask for a detailed inventory and sometimes request the Safety Data Sheet (SDS) for each chemical. Holding onto the documentation helps speed the process, ensuring nobody works in the dark.
Informing everyone—from janitorial staff to new graduate researchers—keeps surprises to a minimum. Posting handling and disposal guidelines right above workbenches, in plain language, gets everyone on the same page. Mistakes drop, near-misses shrink, and reruns of the same close call get less likely.
Some corners of the world still lack safe disposal programs. Here, forming partnerships with local universities or environmental groups can build bridges to better practices. Even starting a conversation around a shared bench can reveal hidden resources. In my experience, a quick talk led to a partnership with a neighboring institution and safer procedures for both labs.
Temptation to rush always hangs around at the end of the day. Still, treating every gram of TEMPO as a responsibility—backed by careful habits and real accountability—protects water, people, and places we care about. A little patience today keeps more doors open for tomorrow.
| Names | |
| Preferred IUPAC name | 2,2,6,6-Tetramethyl-4-oxopiperidin-1-oxyl |
| Other names |
4-Oxo-TEMPO TEMPONE 4-Oxopiperidinooxy 2,2,6,6-Tetramethylpiperidin-4-one-N-oxyl TEMPON |
| Pronunciation | /ˌtuː tuː sɪks sɪks ˌtɛtrəˈmɛθəl fɔːr ˈɒksəʊ paɪˌpɛrɪˈdɪnəʊksi/ |
| Identifiers | |
| CAS Number | 2226-96-2 |
| Beilstein Reference | 1366547 |
| ChEBI | CHEBI:27346 |
| ChEMBL | CHEMBL1201041 |
| ChemSpider | 68011 |
| DrugBank | DB07912 |
| ECHA InfoCard | 20a3d9d8-8578-4943-bdad-7d380fc0c166 |
| EC Number | 1.1.3.8 |
| Gmelin Reference | 42159 |
| KEGG | C01745 |
| MeSH | D017973 |
| PubChem CID | 5806 |
| RTECS number | RR0350000 |
| UNII | D8P41XD8FV |
| UN number | UN3276 |
| CompTox Dashboard (EPA) | DTXSID9021392 |
| Properties | |
| Chemical formula | C9H17NO2 |
| Molar mass | 156.24 g/mol |
| Appearance | Red solid |
| Odor | Characteristic |
| Density | 1.06 g/cm³ |
| Solubility in water | slightly soluble |
| log P | 0.9 |
| Vapor pressure | 0.01 mmHg (25°C) |
| Acidity (pKa) | 20.2 (H2O) |
| Basicity (pKb) | 6.12 |
| Magnetic susceptibility (χ) | 1.18 × 10⁻³ cm³/mol |
| Refractive index (nD) | 1.463 |
| Viscosity | 108 cP (25°C) |
| Dipole moment | 3.14 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 321.3 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -17.5 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | –3758 kJ·mol⁻¹ |
| Pharmacology | |
| ATC code | D02BX08 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes skin irritation. Causes serious eye irritation. Suspected of causing genetic defects. Toxic to aquatic life with long lasting effects. |
| GHS labelling | GHS07, GHS08 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H302, H315, H319, H335 |
| Precautionary statements | P210, P233, P240, P241, P280, P305+P351+P338, P337+P313, P370+P378 |
| NFPA 704 (fire diamond) | 1-1-0-ox |
| Flash point | Flash point: >110°C |
| Autoignition temperature | 238 °C |
| Lethal dose or concentration | LD₅₀ Oral rat: 750 mg/kg |
| LD50 (median dose) | LD50 (median dose): Oral rat 1800 mg/kg |
| NIOSH | WF4950000 |
| REL (Recommended) | 10 g |
| Related compounds | |
| Related compounds |
2,2,6,6-Tetramethylpiperidine TEMPOL TEMPAMINE PROXYL TEMPO-acetoxymethyl ester |
