2,2,6,6-Tetramethylpiperidinooxy, known in many labs as TEMPO, first appeared in literature in the 1960s, surfacing during a rising wave of organic free radical research. Its birth came from the hands of scientists looking beyond traditional stable molecules, trying to break through the limitations found with earlier nitroxide radicals. Instead of keeping to the expected fleeting radicals, chemists working with TEMPO found a molecule that stood the tests of time, light, and air. From its debut, researchers have leaned on this compound’s robust stability to crack open reactions that, for decades, seemed out of reach. Years of peer-reviewed studies, expert-led symposia, and shared lab notes built a foundation of trust for TEMPO that’s rare in synthetic chemistry.
TEMPO carries a reputation as both workhorse and innovator. This molecule crops up not just in academic research but also in production of fine chemicals, bleach products, and specialized polymers. Its widespread adoption signals more than just a scientific curiosity; companies and universities see it as a real solution to tough transformation challenges. Whether used as an oxidant, catalyst, or probe, TEMPO provides clarity and consistency through multiple steps of a chemical process, all while giving scientists room to customize or modify its performance.
TEMPO comes as a reddish-orange solid, often as crystalline powder, melting just above 36°C and boasting a boiling point that rides above 135°C under low pressure. Its structure, featuring four methyl groups tightly hugging a piperidine ring, keeps the nitroxyl radical secure yet reactive at its single oxygen atom. This balance allows TEMPO to stand strong in open air, holding its electronic structure against degradation. Solubility in organic solvents like acetone, ethanol, and dichloromethane makes it easy to integrate into various systems, and with a measured molecular weight around 156 g/mol, it fits neatly into reaction equations or scale-up plans.
Bottles labeled TEMPO must meet high standards, generally promising purity higher than 98%. Suppliers often print batch numbers, recommended storage conditions, and UN chemical codes—details that build accountability for labs dialing in on reproducibility. Labels lay out guidelines for shelf life, shipping regulations, and warnings about strong oxidizers or moisture sensitivity. Manufacturers describe the particle size, which helps teams pick the right reagent for slurry or solution-based processes. Data sheets also include spectral signatures and certificate analysis, allowing buyers to match their needs with documented facts rather than guesswork.
Chemists create TEMPO by oxidizing 2,2,6,6-tetramethylpiperidine using reagents like m-chloroperoxybenzoic acid in organic mediums. Early recipes leaned on traditional oxidants, but process improvements brought more efficient, greener solvents. Reproducibility improved once manufacturers introduced in-line purity checks and better handling of exothermic steps. The shift toward greener chemistry also led to adaptation of more environmentally friendly oxidants, reducing hazardous byproducts. Years of refining brought yields up, waste down, and costs in line with broader market expectations.
TEMPO distinguishes itself by catalyzing the oxidation of alcohols to aldehydes or ketones under mild conditions. The presence of its unpaired electron makes it a singular choice for one-electron transfer reactions, which play a crucial part in specialty synthesis. Derivatives and analogs emerged as interest grew; alkylated or acylated versions broaden the reactivity window, opening chances for precision in targeted reactions. Chemists found that tweaking TEMPO’s environment—adjusting solvent, temperature, or counterions—lets them fine-tune reaction rates, side product content, or selectivity without surrendering yield. Electrochemical and photo-induced variations on TEMPO chemistry now fuel cutting-edge redox processes and energy storage materials research.
Whether called 2,2,6,6-tetramethylpiperidine-1-oxyl, 1-oxyl-2,2,6,6-tetramethylpiperidine, or just TEMPO, this compound shows up under a parade of synonyms in lab catalogs and technical reports. Commercial products often link TEMPO in name to its parental backbone (piperidine nitroxide radical), yet experienced hands know to double-check chemical abstracts and registry numbers to keep procurement mistakes off the bench. Distributor or industrial brand names sometimes merge in descriptors like “free radical stabilizer” or “oxidation catalyst,” creating a patchwork of identities under a clear chemical umbrella.
Working safely with TEMPO comes from respect for its oxidative power. I have always relied on properly ventilated hoods, nitrile gloves, and safety glasses to avoid direct contact. Spent solvent management deserves special care, given the potential for residual radical activity. Data sheets highlight the compound’s irritating properties and the best strategies for accidental exposure. Storage away from heat sources, acids, and bases keeps the radical stable and reduces fire risk. Emergency procedures spell out steps for spills and recommend calcium hypochlorite-neutralizing strategies based on real-world lab incidents. Robust training for new users forms a critical pillar in responsible chemical stewardship.
In my years watching and participating in chemical research, TEMPO’s versatility remains unmatched. Chemists use it for selective oxidation in organic synthesis, advancing drug candidate design, flavor chemistry, and specialty polymer production. Material scientists rely on TEMPO to functionalize surfaces, make redox-active supports, or tailor catalytic frameworks for complex transformations. Outside pure chemistry, biology teams incorporate it in spin labeling for structural studies using electron spin resonance, nudging the boundaries of protein analysis. Formal industrial uses show up in cellulose oxidation—paving the way for bio-based materials—and lithium-based battery technologies. Real-world impact tracks not just through academic journals but in patents—each time innovation teams turn to this compound for performance and reliability.
Groups around the world continue exploring what else TEMPO can offer. I often come across fresh publications highlighting new catalyst cycles or eco-friendlier transformations. Green chemistry pushes demand for milder, safer, and more scalable oxidation protocols, and TEMPO’s track record keeps it front of mind for grant writers and start-up founders alike. Sensing technology also picks up on TEMPO’s ability to interact with radical species, opening doors for smart diagnostic tools in environmental and biomedical fields. University-industry partnerships drive pilot projects aiming to cut down on chemical waste while retaining the precision only TEMPO delivers. Every study moves the discussion closer to a general toolkit for future sustainable labs.
Studies into TEMPO’s safety show low acute toxicity at levels typical for lab or industrial use, yet repeated or high-level exposure raises red flags for skin and respiratory irritation. Chronic exposure animal studies suggest organ stress at significant doses, pushing labs and regulators to keep strict occupational limits. Scientists trace metabolites using labeled compounds, finding relatively rapid excretion in mammals but spotting concerns over potential long-term impacts. Environmental breakdown shows incomplete mineralization, prompting more research on safe wastewater treatment. My own experience lines up with the literature: short exposures in well-controlled environments keep risk manageable, but long-term safety depends on vigilant engineering controls and research into alternative, biodegradable variants.
Looking ahead, I see TEMPO poised to support broader moves toward sustainable technology. Battery developers, green chemical manufacturers, and even medical imaging experts keep pushing TEMPO’s limits. Industry wants cheaper, easier-to-handle versions, spurring continued work on stable, high-purity forms and new derivatives. Regulatory changes may shape how researchers use the compound in coming years, especially if new findings push for tighter environmental controls. Collaborations across fields inject fresh ideas into TEMPO chemistry, hinting at next-generation materials or cleaner energy applications. The story of TEMPO continues as a marker of the power of curiosity, persistence, and a dash of chemical ingenuity—always a step ahead, backed by both hard evidence and community experience.
Walk into most chemical labs and you’ll find a range of substances that look harmless but pull plenty of weight behind the scenes. 2,2,6,6-Tetramethylpiperidinooxy—called TEMPO by chemists—belongs in that group. TEMPO isn’t there just to fill reagent shelves. It serves as a stable radical, which means it has one unpaired electron. That feature drives its reactivity and makes it valuable, especially for oxidation reactions. TEMPO swaps electrons in a predictable way, making it good for turning alcohols into aldehydes or ketones. Small changes in these steps play a massive role in making pharmaceuticals or components for electronics. Some larger manufacturing plants rely on TEMPO catalysis to streamline these reactions and cut waste.
I work with researchers who tinker with cellulose—the stuff in plants—looking for ways to make biodegradable plastics. They depend on TEMPO to alter cellulose fibers for better material properties. TEMPO helps transform wood pulp into nanofibers, boosting the strength and flexibility of eco-friendly packaging. This approach reduces the need for petroleum-based plastic, showing how chemical tools can push real sustainability goals.
You won’t see TEMPO sitting behind a pharmacy counter, but it has shaped plenty of medical advances. TEMPO derivatives act as antioxidants. They scavenge free radicals that damage cells, so scientists have tried using these molecules in experimental treatments for oxidative stress-related diseases. TEMPO’s stability makes it a reliable probe in electron spin resonance (ESR) applications, which helps researchers study molecular structures, free radicals, and other complex processes in the body. ESR with TEMPO has improved how scientists detect subtle changes in blood or tissue samples, offering earlier signals for diseases like Alzheimer’s.
Environmental cleanup crews face challenges that need more than shovels and hope. TEMPO plays a part in some water treatment setups. It helps break down persistent pollutants, such as phenols and colorants, that resist conventional cleaning methods. Using TEMPO-based processes, some companies see better breakdown rates for these chemicals, offering cleaner water without extra harsh byproducts. The environmental sector benefits from this because treating water with fewer chemicals means less downstream waste and less chance for contamination in local ecosystems.
Chemical use always shoulders some risk. While TEMPO’s stability makes it less likely to form dangerous byproducts compared to some radicals, safe handling remains vital. Accidents happen quickly with concentrated reagents, and industry guidelines stress solid safety training. Another point to consider: the price and availability of TEMPO. Fluctuations happen, linked to supply chain hiccups, demand from advanced material sectors, and raw material costs. Investing in chemistry that can recycle or reuse TEMPO offers a way to stretch resources and keep costs stable.
TEMPO does not make headlines, but it quietly powers important scientific and industrial steps. Its role reaches from labs straight into our ordinary lives, showing how molecules we rarely hear about influence products, health research, and even clean air and water. We need chemists and manufacturers to keep searching for safer, more affordable ways to use chemicals like TEMPO if we want any hope of keeping our world running smoothly without creating new problems in the process.
A lot of folks in labs and industry come across 2,2,6,6-Tetramethylpiperidinooxy—usually called TEMPO—every day. It acts as a stable free radical, plays a role in organic synthesis, and pops up as a polymerization catalyst. The name might not strike fear, but thoughtful handling matters even with the most familiar materials.
Sitting on a shelf in a brown glass bottle, TEMPO looks just like another bit of science kit. I remember seeing its bright red color for the first time during a college research project—right alongside flammable solvents and acids. The trouble is, color and calm packaging never tell the full story. Everyone working with chemicals needs more than a data sheet; they need to know what happens if things go wrong.
TEMPO irritates the skin, eyes, and respiratory passages. If you get it on your hands, you might notice a burning or itchy feeling. Breathe in the dust or vapors, and you risk fits of coughing or sore throat. The safety data sheets draw a clear picture: avoid letting it touch your skin or eyes, avoid inhalation, and absolutely keep it away from food and drinks.
We can look to studies in animals to understand what’s possible. Published toxicity data show TEMPO can affect organs at higher doses—especially the liver and kidney in rodents—if animals receive repeated, large amounts. The concentrations used in research don’t often reach such extremes, but risk comes from repeated small exposures, too. There’s no evidence TEMPO causes cancer in humans, yet nobody should call it innocuous.
In actual lab work, keeping exposures low relies on basic routines: gloves, goggles, fume hoods, and no food near the bench. These aren’t just rules for newcomers. Even folks with years behind them forget safety sometimes, thinking familiarity breeds immunity. I’ve seen old hands splash themselves when distracted, or leave bottles open while answering emails. Small habits matter.
The National Institute for Occupational Safety and Health describes TEMPO as a low acute toxin, but still puts it on the chemical watchlist. That tells you precautions pay off. I always made sure to store TEMPO away from heat or direct sun because it can turn unstable with enough energy. It doesn’t mix well with strong reducing agents or acids. A spill cleanup means more than just a paper towel—proper disposal and reporting are critical.
I’ve talked with safety officers across several universities and industry labs, and they all echo the same message: training and routine matter more than trying to memorize hundreds of safety ratings. Regular review of procedures, keeping updated material safety data sheets handy, and making sure everyone—from students to seasoned chemists—watches for signs of exposure forms the core of chemical safety.
TEMPO’s usefulness in science and manufacturing is established. Nobody wants to avoid technology that brings new medicines, lighter plastics, or more efficient batteries. The key comes from knowing what you’re handling and respecting the risks. Eyes open, gloves on, and safety always one step ahead of routine—that mindset turns a hazardous compound into a tool, not a trap.
A jar of 2,2,6,6-Tetramethylpiperidinooxy, better known as TEMPO, sits innocently on many chemistry shelves. Don’t let the unassuming vibe fool you—there’s real science and real risk packed in this nitroxyl radical. Forget stale lab rules for a second. Poor storage eats through budgets and endangers real people. That lesson hit hard for me, the day we lost two grams to careless handling and nearly triggered an evacuation.
TEMPO stands up pretty well to day-to-day lab use, thanks to its stable structure built around four methyl groups shielding the core. Even so, air and sunlight go after it—oxidation happens faster than folks expect, and high humidity turns reliable material into a gummy mess. Keep it in a tightly sealed, amber glass container. A plastic bottle may react with the compound under certain circumstances, especially if the polymer grade is unknown or cheap. Tossing the jar on any random shelf is asking for trouble.
Heat wrecks TEMPO in a flash. Store it below 30°C, but don’t freeze it unless specifically recommended by suppliers—repeated freeze-thaw cycles clump the powder and make weighing impossible. Most university labs settle on room temperature, away from windows. I’ve seen students store it beside acid baths or even wet solvents—big mistake. Vapors drift, lids get loose, and ruin follows. Always dedicate a clean, dry spot in a ventilated chemical cabinet.
Manufacturer safety data sheets all hammer the same points: no direct sunlight, no open flames, minimal moisture. Real-world failure stories say even more. In one published case, leaving the container open for just five minutes on a humid summer day cut activity by half. Another research group noted a stubborn, sticky residue after six months in a poorly-sealed plastic bottle—lost time, lost experiments, wasted funds.
I always label TEMPO with the exact opening date. We chuck anything older than a year—no exceptions. Gloved hands only touch the container to protect from skin irritation, but also to keep sweat away (TEMPO eats skin upon long contact). Opening the bottle quickly, without dallying in humid air, prevents clumping. I keep a small silica gel sachet inside the storage cabinet, not inside the bottle, to absorb stray water vapor.
Cross-contamination plagues undergrad stockrooms. Cleaning the scoop thoroughly before and after each use curbs surprises later. In rare cases, suppliers package TEMPO under an inert gas blanket; labs running critical, high-purity syntheses will want to maintain that atmosphere with argon or nitrogen. Most daily users don’t need to go that far, but students unfamiliar with oxygen-sensitive chemistry often let air rush in, then wonder why yields drop off a cliff.
Our lab stopped leaving all reagents on communal benches. We built in checks: quarterly supply audits, regular container checks for moisture or irregular clumping, and enforced cleanup routines. Simple solutions like amber glass jars and airtight lids made more difference than pricey storage units.
TEMPO isn’t the most hazardous reagent you’ll meet, but treating it casually offers up real headaches. Learning from faded labels and ruined powder builds scientific muscle memory—one we use every day with more reactive compounds. Store it smart, so the work and the people stay safe.
2,2,6,6-Tetramethylpiperidinooxy goes by another name that researchers and lab workers know well: TEMPO. Its molecular formula is C9H18NO. The structure is what delivers its punch. TEMPO is built around a six-membered nitrogen-containing ring. Each corner, in this case, the 2 and 6 positions, carries two methyl groups. That adds up to four methyl groups sticking off the main ring — which, in simple terms, makes the molecule pretty bulky for its size. Plus, there is a nitroxyl (N–O•) group attached to the ring’s nitrogen atom. That little dot means it is a stable free radical, and that puts TEMPO in a league of its own.
In any synthetic lab or chemical manufacturing plant, radical chemistry turns heads for a good reason — radicals tend to be reactive and short-lived. TEMPO breaks the rule. Researchers in the 1960s knew they found something special when they realized this molecule could sit happily as a radical at room temperature, without blowing up or disappearing.
TEMPO owes much of this stability to its chemical structure. The heavy methyl groups piled onto the piperidine ring provide extra bulk, shielding the nitroxyl radical from reactions that would normally snuff it out. It feels almost counterintuitive, but making the molecular neighborhood crowded protects the radical center from troublemakers — much like a bouncer at the door of a crowded club.
This combination of stability and unique reactivity has helped chemists get creative with oxidation reactions. For example, in the paper and pulp industries, TEMPO-based oxidation swaps out old-school harsh chemicals for processes that work at room temperature and under controlled conditions. That can cut down on dangerous byproducts and environmental waste.
Take household bleach out of the picture, and it’s easy to see the need for milder and more selective oxidation. TEMPO makes it possible to turn alcohol groups into aldehydes or acids without chewing up everything else nearby. In my own postgraduate research, swapping out typical oxidants for TEMPO saved headaches on scaleups. Yields stayed strong and side-products dropped. It’s not just my story; countless reports back this up.
Researchers have taken advantage of TEMPO’s radical stability in polymer science too. Controlled radical polymerization, often a tricky process, benefits a lot from the gentle hand that TEMPO brings. The free radical polymer chains grow in a well-managed way, making plastics and materials with properties designers want — from medical devices to next-gen packaging. Every time a new application comes up, the molecule’s unique structure keeps it in play.
TEMPO isn’t perfect. It isn’t the cheapest reagent to produce at scale, and not every system tolerates it. In water treatment, for example, cost and reactivity with impurities limit its options. But ongoing research aims to make analogues that offer the same benefits at a lower price or with added environmental perks. Creating more sustainable synthesis methods could open the door for broader practical use, especially in greener industry settings. Teams around the world keep pushing for these improvements, recognizing that a small tweak in a molecule’s structure unlocks big changes in what our chemical world can achieve.
2,2,6,6-Tetramethylpiperidinooxy, usually called TEMPO, shows up in labs worldwide. Most researchers recognize it by its bright orange-red color and know it by feel—a crystalline, free-flowing powder. You rarely see TEMPO packaged for direct consumer use. Chemists and industrial labs get it straight from supply houses, always kept safe from moisture and light because both can cut into its shelf life and mess with its performance in synthesis.
Chemicals like TEMPO don’t just get scooped into any old box. Suppliers usually choose amber glass bottles or high-density polyethylene containers because these keep out light and hold up against chemical seepage. My own lab would never risk using TEMPO from a clear plastic jar left out on a bench—for a reason. The color fades, the powder forms clumps, and a reaction that’s supposed to be precise starts throwing curveballs.
Chemical companies seal TEMPO tightly, often with double-sealed caps and extra foil or plastic linings to keep air out. Small bottles are more common—5-gram, 25-gram, maybe up to 100 grams—since labs want to use it fresh and not risk wasting expensive material. Weight labels stay front and center on both the bottle and its shipping box. This makes tracking easy and reduces those mad scrambles to check “Did we actually order the right amount?”
TEMPO isn’t something your local hardware store carries. Getting it usually means working with specialized chemical distributors who understand how to package materials that turn hazardous with the wrong exposure. If the flask tips over or the bottle cap loosens in transit, labs face inventory loss and safety issues. The supply chain does its part—cushioning bottles, printing hazard codes, attaching Material Safety Data Sheets (MSDS), and sometimes adding ice packs or desiccants in warmer climates to keep the powder stable.
From my experience, reordering TEMPO after getting a poorly stored batch means headaches. Contamination risk goes up every day a jar stays open—a tiny shift in air, temperature, or contact with humidity can ruin months of lab work. Labs pay more up front for reliably packaged product, because a ruined test or failed production run easily outweighs a few dollars saved by cutting corners.
The demand for traceability also plays a part. QR codes and batch numbers stamped right onto bottles now let chemists and compliance officers track exactly where and when each bottle was filled. This isn’t just bureaucracy—having a trace line means a lot if a product recall or process question pops up six months down the road.
A few solutions already help with the pain points. Self-sealing lids cut down on spills and oxygen leaks. Smaller one-use pouches and pre-measured vials mean less handling and lower contamination risk, plus less waste after reaction setups.
Still, I’d like to see more tamper-proof designs and biodegradable containers. The chemical industry moves slowly, but some companies already roll out eco-friendly bottles and safer storage kits. With tighter environmental rules and more focus on lab safety, there’s a push for both smarter packaging and better training for everyone touching hazardous materials.
TEMPO’s sensitivity to oxidation, sunlight, and moisture isn’t just lab gossip—papers like “Storage and Handling of Nitroxide Radicals” (J. Org. Chem. 2003) point out real-world problems when packaging fails. Industry standards—like ISO 9001 for quality and GHS labeling rules for hazards—underline what dedicated chemical suppliers already enforce in practice.
Relying on proven packaging and conscientious suppliers makes sure useful chemicals like TEMPO don’t become costly mistakes on arrival. Proper handling gets backed by real science and reinforced by tight standards, and anyone who’s worked in a lab, as I have, knows why every little bit of effort in packaging keeps research and industry running.
| Names | |
| Preferred IUPAC name | 2,2,6,6-Tetramethyl-1-oxylpiperidine |
| Other names |
TEMPOL 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl 2,2,6,6-Tetramethylpiperidine 1-oxyl TEMPO 1-Oxyl-2,2,6,6-tetramethylpiperidine |
| Pronunciation | /ˌtuː tuː sɪks sɪks ˌtɛtrəˈmɛθəl paɪˌpɛrɪˈdiːnoʊˌɒksi/ |
| Identifiers | |
| CAS Number | 2226-96-2 |
| Beilstein Reference | 1367786 |
| ChEBI | CHEBI:45628 |
| ChEMBL | CHEMBL1237 |
| ChemSpider | 7145 |
| DrugBank | DB01637 |
| ECHA InfoCard | ECHA InfoCard: 100.011.719 |
| EC Number | 1.10.3.8 |
| Gmelin Reference | 90832 |
| KEGG | C02331 |
| MeSH | D017945 |
| PubChem CID | 5961 |
| RTECS number | RG3460000 |
| UNII | V9F6MZ2JZ4 |
| UN number | UN3276 |
| CompTox Dashboard (EPA) | DTXSID2020438 |
| Properties | |
| Chemical formula | C9H18NO |
| Molar mass | 156.24 g/mol |
| Appearance | Red solid |
| Odor | Odorless |
| Density | 1.007 g/mL |
| Solubility in water | slightly soluble |
| log P | 2.0 |
| Vapor pressure | 0.0057 mmHg (25 °C) |
| Acidity (pKa) | 18.5 |
| Basicity (pKb) | 7.9 |
| Magnetic susceptibility (χ) | χ = 1.21×10⁻³ |
| Refractive index (nD) | 1.463 |
| Viscosity | 10 cP (20 °C) |
| Dipole moment | 3.14 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 319.3 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -10.7 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -4495 kJ·mol⁻¹ |
| Pharmacology | |
| ATC code | D02BX08 |
| Hazards | |
| Main hazards | Harmful if swallowed, causes skin irritation, causes serious eye irritation, may cause respiratory irritation |
| GHS labelling | GHS02, GHS07 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H226, H302, H315, H319, H335 |
| Precautionary statements | P210, P233, P240, P241, P242, P243, P261, P264, P271, P273, P280, P302+P352, P304+P340, P305+P351+P338, P312, P337+P313, P362+P364, P370+P378, P403+P235, P405, P501 |
| NFPA 704 (fire diamond) | 1-3-1 |
| Flash point | Flash point: 110°C |
| Autoignition temperature | 245 °C (473 °F; 518 K) |
| Lethal dose or concentration | LD50 oral rat 2700 mg/kg |
| LD50 (median dose) | LD50 (median dose): Oral-rat LD50: 268 mg/kg |
| NIOSH | KWQ7 |
| PEL (Permissible) | PEL not established |
| REL (Recommended) | 200 mg |
| Related compounds | |
| Related compounds |
TEMPO 2-sulfonic acid TEMPOL 4-Hydroxy-TEMPO Oxoammonium salts Proxyl ABNO |
