Chemists have long relied on aromatic derivatives for new materials, starting in the early 20th century as synthetic organic chemistry began to grow. The backbone structure connecting phenylenedimethylidene groups with rigid bicyclic and sulfonic acid moieties signals a significant step in custom molecule design, targeting both reactivity and practical usability. Back then, research focused on creating more robust intermediates for dyes and polymers, aiming for compounds that could withstand harsh industrial processes. Intensive research in the 1980s and 1990s unlocked scalable methods for incorporating bicyclic frameworks and sulfonic groups in a single molecule, setting the stage for today’s more complex synthesis. Real innovation came when researchers could precisely control the stereochemistry, pushing (E-E)-3,3'-(1,4-Phenylenedimethylidene)Bis(2-Oxobornane-10-Sulfonic Acid) into focus for advanced material applications and specialty chemicals.
Known in research circles for its ability to impart both rigidity and hydrophilicity, (E-E)-3,3'-BPSA (a commonly used short name) combines a phenylenedimethylidene bridge with oxobornane sulfonic acid units. The product's dual hydrophobic and hydrophilic character brings value in crafting specialty coatings, high-performance resins, and selective ion-exchange materials. Customers tend to encounter this molecule as an off-white crystalline solid, sometimes slightly yellow depending on the manufacturing process. Companies often target purity above 98% to avoid inconsistent chemical performance, since impurities—even below 2%—have spoiled batches and led to costly downtime in production settings. For anyone working on surface modification or polymer functionalization, this molecule stands as a staple in the chemical toolkit.
(E-E)-3,3'-BPSA has a molecular weight hovering near 560 g/mol, and resists solubility in most nonpolar solvents due to dense sulfonic acid groups. Water and polar aprotic solvents—such as DMSO or DMF—break down its lattice structure, dispersing it into clear solutions. The compound shows strong thermal stability, with decomposition temperatures exceeding 280°C. Under UV light, it keeps its integrity, making it useful for resin curing systems exposed to harsh conditions. With sulfonic groups, the acid dissociation constant measures strong acidity—pKa values below 1.2 are not uncommon. I've seen samples stored improperly that began absorbing atmospheric moisture, so proper desiccation matters in lab and production settings. Crystallinity runs high, leading to clean lattice patterns on X-ray diffraction, ideal for analytical confirmation.
Manufacturers post key technical data directly on their labels for clarity. Purity, measured by HPLC or titration, must meet at least 98%, often 99% for research markets. Moisture content needs monitoring as the substance acts hygroscopic; packaging indicates water content, usually below 0.5%. Labels show batch numbers, recommended storage (cool, dry, tightly sealed), and warnings about respiratory and eye exposure due to particulate irritation potential. In most chemical supply chains, UN number and EU REACH compliance appear on the outer carton, alongside standard hazard pictograms for corrosive substances. Every chemist appreciates seeing spectral data—proton NMR and IR signature peaks—linked to batch certificates for reassurance during quality control.
Synthesis heads down a multi-step route, which starts with a Friedel–Crafts alkylation to stitch the phenylenedimethylidene connector. Researchers introduce 2-oxobornane derivatives through Diels-Alder cycloaddition, providing the rigid bicyclic backbone. Sulfonation steps, using chlorosulfonic acid or oleum, place sulfonic acid groups at precise locations. Workups involve neutralization and careful crystallization to avoid product hydrolysis or uncontrolled polymerization. Every step contributes to overall yield; process optimization focuses on reaction temperature control and quick phase separation. In industrial practice, continuous-flow synthesis replaced batch methods for higher throughput and reproducibility, which I’ve seen cut time and cost without sacrificing reproducibility. Final purification includes column chromatography or repeated recrystallization, followed by vacuum drying.
The molecule’s robust skeleton survives a range of transformations—esterification, amidation, and, in focused studies, even Suzuki coupling at the aromatic ring under palladium catalysis. The sulfonic groups support salt formation with alkaline or transition metals, expanding application in catalysis and ion-exchange materials. For those aiming to tweak solubility or tune hydrophilicity, converting the acid groups to their sodium or potassium salts gives better process flexibility. Experiments report successful copolymerization with acrylates and epoxies, creating specialty polymers whose performance boosts its original intent. Oxobornane core survives mild oxidizing and reducing environments; under strong reducing agents some cleavage can occur, so reaction conditions matter. Interested researchers sometimes attach functional ligands, making derivatives useful for diagnostic probes or separation science.
This compound wears several names in literature and markets: Benzylidene Bis(oxobornane Sulfonic Acid), Di-(Bicyclo[2.2.1]Heptanone-10-Sulfonic Acid)-1,4-Phenylene Methanediyl, and simply BPSA in technical shorthand. Trademarks vary; some companies label it under proprietary blends for resin additives or as a specialty cross-linker. Knowing alternate names helps researchers track international references and patents, as translation errors between chemical registries have spurred confusion over regulatory filings.
Despite sounding exotic, (E-E)-3,3'-BPSA fits the expected hazard profile for strong organic acids. Skin and eye contact draws immediate irritation, as documented in the safety data sheets from multiple vendors. Inhalation avoidance comes standard; powder works best in ventilated enclosures or fume hoods. Gloves and splash-resistant goggles go on before opening bags, which often arrive double-lined with moisture barrier pouches. The acid can corrode aluminum, mild steel, and uncoated copper, so only glass or polypropylene equipment holds up for handling and storage. Spill management runs on neutralization protocols—mild sodium carbonate quenching followed by water rinses. Disposal means full compliance with local hazardous waste laws, never drain disposal, as local regulations ban acid and aromatic discharge. In manufacturing environments, dust control and air monitoring limit long-term exposure risk to workers.
(E-E)-3,3'-BPSA surfaces in a spread of industries, often in places where chemical resilience and clarity beat cost or ease. Advanced coatings draw on its combination of rigidity and sulfonic acidity for scratch resistance and gloss retention. Ion-exchange materials, especially those for harsh chemical purification (fluorine, bromine removal systems), benefit from its robust framework. In recent years, specialty polymer designers have leaned into its dual hydrophobic and functional acid nature, building membranes for batteries and water treatment. Analytical chemists test it as a matrix component in MALDI-TOF mass spectrometry. Environmental engineers find value in the high acidity for catalytic reactions in green chemistry—some recent patents highlight its use in catalytic conversion of biomass to value-added fuels.
A look at recent publications points to heavy exploration in tuning the backbone for improved conductivity and lower swelling in polymer electrolytes. Laboratory research takes aim at making composite materials with carbon nanotubes and graphene, seeking synergy between sulfonic acid content and conductivity. High throughput screening platforms have evaluated thousands of chemical variants derived from this backbone for their performance in proton exchange membranes, where only a handful match the chemical and physical stability standards set by (E-E)-3,3'-BPSA. Bringing these insights to practical products depends on bench-scale synthesis improvements that avoid hazardous reagents and reduce waste stream volume—an effort underway in several major chemical firms. In my own experience working on battery research, the compound’s shelf stability and reactivity shaped choices around membrane preparation far more than theoretical capacity numbers.
Published animal studies show acute toxicity ranks as moderate—not benign but well within the manageability range for most organic sulfonic acids. Inhalation and oral exposure cause mucous membrane irritation at doses higher than those typical in controlled lab or industrial settings. Chronic toxicity hasn’t surfaced at low exposure levels, though repeated dermal contact over weeks caused dermatitis in rodent tests. No known carcinogenic or mutagenic effects have been confirmed in peer-reviewed research up to the last five years. Regulatory agencies in the EU and North America have kept exposure guidelines in the low mg/m³ range. That said, safe workplace habits matter, since any strong acid with aromatic character poses escalation risks in a major spill or unplanned exposure scenario.
Rising demand for cleaner and more efficient energy storage systems keeps research momentum high around (E-E)-3,3'-BPSA derivatives. Synthetic chemists now experiment with greener production routes—sulfonating with less hazardous agents, lowering environmental footprint, and reclaiming process solvents. Material engineers project a wider role for this molecule in advanced hydrogel scaffolds, sensing films, and separation membranes. Cross-disciplinary teams see it as a bridge between traditional chemical synthesis and modern material science, especially where toughness and chemical customization overlap. With regulatory focus tightening on hazardous byproducts during synthesis and end-of-life disposal, future versions will almost certainly feature improved degradability and safer handling. As nanotechnology and smart materials develop, functionalized forms of this backbone could enable yet unforeseen applications in diagnostics or environmental clean-up. The track record of adaptability makes it a subject of ongoing study and practical innovation.
Mentioning (E-E)-3,3'-(1,4-Phenylenedimethylidene)Bis(2-Oxobornane-10-Sulfonic Acid) in a chemistry classroom sparks curiosity among students and raises an eyebrow or two in any industry meeting. That long name signals a specialty compound. Years in materials science taught me to look past the strange spellings. The compounds with clunky names often power the quiet revolutions in manufacturing, printing, and electronics.
In daily life, few people consider the chemistry behind the photographs hanging on their walls or the blueprints rolled out on workbenches. Most never realize the precise chemical steps turning digital files into crisp, permanent prints. Printing presses and photographic industries both rely on molecules that help bring these images to life effectively and cleanly. This sulfonic acid derivative, for all its syllables, plays a core part as a photoacid generator (PAG). Engineers and scientists use it because it responds well to UV light. After exposure, it releases acid, starting chemical reactions exactly where a pattern or image should form.
Photoacid generators shape the lifeblood of processes like photolithography. Wander through a modern chip factory, and you’ll find cleanrooms where light etches impossibly fine circuits onto silicon. The precision here depends on these generating molecules. No one wants blurry lines or electrical faults, so specialists favor PAGs that offer detail, stability, and predictable results. In my own work testing industrial resists, I saw what happens with a low-purity or mismatched additive. The difference between a sharp or smeared image comes down to how well a photoacid generator does its job.
Strong results and fine features sound great, but every chemist has concerns about safety and the planet. Sulfonic acids and related compounds can hit water treatment systems if not handled right. Large-scale use shoves companies to face hard questions about disposal. Some research points to next-gen compounds with quicker filtration or neutralization. Others look for alternatives that swap out heavy metals. Still, demand for sharp lines and long-lasting prints keeps these sulfonic-based PAGs near the top of the list.
Many labs and manufacturers tweak their practices to deal with the byproducts of PAGs like this one. Closed-loop systems can recapture chemical residues. I’ve watched teams trim waste by tracking every drop from mixing tanks to rinse water. Simple adjustments, like switching to smaller batch sizes or changing rinse cycles, often cut down the environmental load. These little changes get companies closer to meeting stricter global rules without halting progress.
Chemistry moves quickly, but proven solutions stick around. Companies continue to chase better photoacid generators for faster, cleaner electronics and images. Still, mastering how to use or dispose of these compounds shapes the industry’s future. Anyone walking through the world of printed circuits or large-format prints owes a nod to the chemists behind these complex molecules. With each new use, new concern, and smarter solution, the story of (E-E)-3,3'-(1,4-Phenylenedimethylidene)Bis(2-Oxobornane-10-Sulfonic Acid) grows—and so does the impact on everything from your smartphone to tomorrow’s art.
Working in laboratories and warehouses with chemicals, I’ve seen how one missed detail with storage can lead to much bigger problems. Sometimes, news about chemical accidents hits the headlines, and people wonder why these issues keep cropping up. Most of the time, the answer boils down to small lapses in following storage guidance. For me, storing chemicals never feels like ticking boxes—it’s more personal, almost like protecting the people you work with every day.
Chemicals don’t all behave the same way in storage. Some bottles start fuming at room temperature, others quietly react if air sneaks in, and plenty cause trouble if they get damp. If you’ve worked with strong acids or oxidizers, the instruction is simple: a cool, dry spot, away from sunlight and anything flammable. A regular shelf in a hot room is a recipe for corrosion and nasty gases. The humid air messes up powders, so airtight containers make all the difference. I still remember once years ago, a colleague left a jar loose over the weekend; the smell that Monday morning taught all of us the value of tight lids.
Chemicals love to be kept with friends—just not the wrong ones. Mixing strong acids with bases or combining oxidizers and organic solvents can mean danger. Even if two bottles don’t touch, fumes can leap gaps and kick off trouble. Segregated storage isn’t about paranoia, it's about history—case studies on accidents all say the same thing. Different cabinets for acids, bases, and flammables keep peace in the storage room. It’s a simple fix: color-coded shelves and daily habits.
Many resources list the right temperature, ventilation, and humidity. It’s easy to print out a table and stick it on a wall, but that means nothing if new faces at work skip the training. Over the years, I’ve watched folks forget about PPE or misread hazard labels. Chemical security should feel routine—log entries for orders, locked storage, and periodic checks for leaks or expired stock. One overlooked bottle can cause spills you'll smell for months, or regulations you’ll regret ignoring. Still, some workplaces treat it as a burden instead of daily risk reduction. Good storage is about habits, not just hardware.
The facts come clear in reports from OSHA, NIOSH, and university safety offices. Wrong storage setups feed the biggest lab disasters. Data from the Chemical Safety Board shows accidents linked directly to skipping storage rules, not just fluke reactions. Building-wide ventilation systems and chemical-resistant flooring make a real difference. Everything boils down to a cycle—guidelines from the top reach the floor level, workers take responsibility, and audits dig up gaps before they grow. Sites that blend these elements report fewer incidents and easier regulatory audits.
No one plans to be the reason for a spill or emergency call. Habits built on good information—double-checking incompatible chemicals, using vented storage, discarding old stock, and never leaning on “it’s fine for now”—offer the strongest defense. What’s at stake isn’t just property, but trust from co-workers and the wider community. For everyone who spends time near chemicals, the best reason to store them right is knowing the people you care about are just a wall away.
Anyone who’s spent time in a lab, a janitor’s closet, or even just doing chores around the house has handled chemicals, some far more hazardous than they first appear. Bleach, acetone, ammonia—basic household names—can cause burns, trouble breathing, or worse if handled carelessly. One day in college, pouring bleach into a mop bucket for work-study, I splashed a small dot onto a favorite pair of jeans. The pants ended up ruined, and on top of that, my hands itched for hours, even after two washes. That wasn’t even an industrial chemical, just what most people have sitting under their kitchen sink. It’s a lesson I didn’t forget. Once you’ve seen skin go pink and start to sting, it’s easy to pay more attention to chemical safety labels.
Simple mistakes with chemicals turn into medical emergencies. Mixing ammonia and bleach produces toxic chloramine gas, which can knock you out or send you to the emergency room. Even products like drain cleaner—a common item in the garage—can cause vision loss from one bad spill. In agriculture or construction, some of the treatments and solvents aren’t just irritating. Chronic exposure raises cancer risk, and certain chemicals build up in the liver and kidneys. Safety reports point to mishaps involving caustic soda, pesticides, or solvents at work sites as a big source of injuries. In the United States, poison control centers receive over two million calls each year about chemical exposures, and a chunk of those involve adults who should know better.
Every bottle might come with instructions, but workers and homeowners often skip them, assuming quick jobs don’t need gloves or eye protection. My early jobs taught me to always look for long sleeves, nitrile or thick rubber gloves, and goggles if there’s any risk of splashing. Once you get chemical burns—a sharp white line on your skin or a surprise cough after breathing solvent fumes—it’s hard to wave off protective gear as unnecessary.
Ventilation makes a huge difference, too. Even basic cleaning supplies work best in rooms with open windows or working exhaust fans. Fume hoods in labs aren’t just for show. They keep volatile chemicals from filling up the space or sticking in your nostrils, and they protect everyone around you. Keeping chemicals locked up, separate from food or medicines, helps prevent dangerous mix-ups.Hospitals see people with burns, stress asthma, and lifelong scarring from accidents that better habits could have prevented. Groups like OSHA and NIOSH offer clear standards for workplace safety, insisting on training, signs, and spill kits. Gloves and goggles cost little compared to the bill for an ER visit or long-term lung problems. Washing hands thoroughly and labeling every bottle—even homemade cleaning mixes—reduces confusion. Speaking from experience, storing ammonia-based glass cleaner apart from acids, bleach, or peroxides keeps the air safe and your nerves calm.
A smart culture around chemicals means teaching people from a young age about the risks. Hands-on demonstrations stick in memory better than lectures or instruction sheets. For employers, running regular drills, keeping data sheets handy, and supplying personal protection must become daily habit. Good ventilation, clear labeling, and steady attention to changes in procedures create workplaces and homes where chemicals serve our needs without putting us in harm’s way.
Chemistry always fascinated me because it’s so exact. Years ago, as a student working late in the lab, the idea of skipping over simple molecular weights seemed tempting. I quickly learned a hard truth: mistakes at this basic level make every calculation that follows completely unreliable. It’s similar with cooking—forget just one ingredient or measure it wrong, and the whole dish comes out off. In a production environment or even a school experiment, the difference between success and failure can rest on understanding exactly what the product is at a molecular level.
Doctors prescribe drugs based on dosage, which depends directly on molecular weight. Engineers designing a new battery or solar cell rely on the exact chemical formula to achieve efficiency and safety. Food scientists track additives and preservatives all the way down to the atoms. These decisions impact everyday lives, from keeping patients healthy to stopping contaminants in a food supply. No one ignores product identity or its weight when the risk is real.
Just taking a look at an unknown compound and making guesses about its makeup doesn’t work. Years ago, a peer insisted he could guess a white powder’s identity from smell and appearance—he failed spectacularly. Lab tools like spectroscopy or titration, and reliable chemical references, serve as the truth-tellers. Over-reliance on intuition alone always led to messy outcomes.
Working in a manufacturing setting, I saw how even a tiny mislabeling or calculation error led to tons of wasted raw materials. In chemical companies, mixing slightly off-target amounts can shut down entire machines. A solid record of a product’s chemical formula and weight keeps operations running and, most importantly, people safe.
Accurate molecular weights and formulas give teams common ground. Pharmacists, engineers, and regulators all use the same language. Safety data sheets depend on this information to guide first responders when accidents happen. Modifying a process to scale production counts on knowing exactly what the starting material can do, so the end product meets performance and purity standards.
I’ve seen situations where products failed quality control because of incomplete or ambiguous product data. Correcting this meant tracing the mistake right back to the paperwork describing the chemical structure and the numbers that followed it. Improvements to traceability and batch documentation—now industry standards—stem directly from these cautionary tales.
Mistakes and mix-ups don’t disappear with experience, but good habits help. Starting every project with a double-check of the chemical formula and a review of reliable sources became second nature. Digital tools and software help catch human errors and make calculations consistent—especially when scaling up from a beaker to a factory tank. Audits and training sessions create an environment where attention to detail becomes routine.
Science thrives on clarity, and details like the molecular weight and chemical formula represent the foundation for so much more. Getting these numbers right isn’t about trivia or box-ticking—it’s about trust, safety, and quality, whether the stakes involve consumer goods, life-saving medicine, or next-generation technology.
Every day, chemistry students and lab workers alike ask one simple question: Will this stuff dissolve? The reason for the question comes down to simplicity and waste. If a compound readily dissolves in water, no one scrambles for expensive organic solvents or rigs up complicated apparatus just to see the results. Water solubility influences everything from making medicine to keeping a factory line moving. Look at the way pharmacies compound cough syrup, or food scientists blend vitamins into juice; both rely on solubility.
Making predictions isn’t as clear-cut as reading a data sheet. Consider the shape and bonds inside a compound. Ionic compounds like sodium chloride dive into water, breaking apart into sodium and chloride ions. Our bodies rely on that, since nerves need sodium to fire. On the flip side, many organic molecules are like oil in a glass—they refuse to mix. Most oils, greases, and waxes come packed with long hydrocarbon chains, which water ignores.
A rule I follow: “Like dissolves like.” Polar molecules mix with polar solvents, and nonpolar molecules run with nonpolar groups. Think about trying to mix sugar in coffee. Easy. Sugar is polar; so is water. Now try dissolving candle wax in that same coffee—no luck. But add hexane, or lighter fluid, and the wax melts away. For most folks working in laboratories, those predictions save time and budget after just a few tries.
Experience teaches the hidden wrinkles. Calcium carbonate barely budges in water, which makes it perfect for antacids that don’t rapidly dissolve inside the bottle. On the other side, acetone smashes through nail polish quickly because its polar-aprotic nature sneaks into all sorts of chemical interactions. Solubility controls the time it takes to clean paint brushes, or the speed at which fertilizers reach roots.
Scientific research depends heavily on solubility. In the pharmaceutical world, nearly 40% of new drugs fall behind in development because their molecules stay stubbornly undissolved. I spent weeks as an intern watching chemists shake vials, hoping for clear solutions. Sometimes the answer was a pH tweak. Sometimes a different solvent unlocked the compound. The process doesn’t frustrate just rookies; senior researchers, too, fight and sometimes lose to poor solubility.
Rather than memorizing tables, think about chemical structure and charge. Polarity, ionic charge, and the size of molecules point in the right direction. Don’t just ask if a compound is soluble in water—try ethanol, acetone, or chloroform in the lab. Details found in journals and handbooks from trusted sources help build good habits. Looking up peer-reviewed articles on solubility will always beat guessing.
Environmental safety always calls for a review. Choosing solvents with lower toxicity and easier disposal can curb hazards down the road. Chemists and researchers can address water pollution by steering away from harsh solvents like benzene and picking greener options like ethanol. Teachers introduce these priorities to students early now, teaching the next generation of scientists to think about safety long before the first beaker fills up.
Solubility shapes safety, cost, and final results long before a product ever reaches the end user. Knowing how and why a compound dissolves builds stronger, safer science—and in practice, saves a lot of time and money.
| Names | |
| Preferred IUPAC name | (E,E)-3,3'-(1,4-Phenylene-dimethylidene)bis(2-oxocamphor-10-sulfonic acid) |
| Other names |
K-BESSA K-BESSA acid BESSA |
| Pronunciation | /ˈiː iː θriː θriː wʌn faɪv ˈfɛnaɪliːn daɪˈmɛθɪlɪdiːn baɪs tuː ɒksəʊˈbɔːneɪn tɛn sʌlˈfɒnɪk ˈæsɪd/ |
| Identifiers | |
| CAS Number | 91232-82-9 |
| 3D model (JSmol) | `3DModel:JSmol: C=CC1(CCC2(C1CCC3C2C(=O)CC4(C3CCC(C4)S(=O)(=O)O)C)S(=O)(=O)O)C5=CC=C(C=C5)C=C(C6(CCC7(C6CCC8C7C(=O)CC9(C8CCC(C9)S(=O)(=O)O)C)S(=O)(=O)O)` |
| Beilstein Reference | 1408731 |
| ChEBI | CHEBI:53374 |
| ChEMBL | CHEMBL2105689 |
| ChemSpider | 23732036 |
| DrugBank | DB16335 |
| ECHA InfoCard | 035d53f3-ecfd-43af-ba04-51e8a24847fb |
| EC Number | 3.1.3.16 |
| Gmelin Reference | 107132.3 |
| KEGG | C22103 |
| MeSH | C15H20O7S2 |
| PubChem CID | 155157785 |
| RTECS number | VV8950000 |
| UNII | 833L9PQZ20 |
| UN number | 3265 |
| CompTox Dashboard (EPA) | DTXSID30896892 |
| Properties | |
| Chemical formula | C32H38O10S2 |
| Molar mass | C38H46O10S2 |
| Appearance | White solid |
| Odor | odorless |
| Density | 1.38 g/cm³ |
| Solubility in water | soluble |
| log P | -0.7 |
| Acidity (pKa) | 1.77 |
| Basicity (pKb) | 6.13 |
| Magnetic susceptibility (χ) | -4.05 × 10⁻⁴ |
| Refractive index (nD) | 1.630 |
| Viscosity | 370-570 mPa·s |
| Dipole moment | 8.15 Debye |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 391.2 J·K⁻¹·mol⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1711.7 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -3736 kJ mol⁻¹ |
| Pharmacology | |
| ATC code | D02AE01 |
| Hazards | |
| Main hazards | H315, H319, H335 |
| GHS labelling | GHS07, GHS05 |
| Pictograms | GHS05,GHS07 |
| Signal word | Warning |
| Hazard statements | H315, H319, H335 |
| Precautionary statements | P261, P264, P271, P272, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P333+P313, P337+P313, P362+P364, P501 |
| NFPA 704 (fire diamond) | 1-1-0 |
| Flash point | > 315 °C |
| LD50 (median dose) | > 5000 mg/kg (rat) |
| PEL (Permissible) | No PEL established |
| REL (Recommended) | 0.5 mg/m³ |
| Related compounds | |
| Related compounds |
Camphorsulfonic acid Bornane-10-sulfonic acid 1,4-Phenylenediacetic acid Menthone sulfonic acid Isobornyl sulfonic acid |
