Early interest in 2-Phenylpropionic Acid, sometimes called alpha-phenylpropionic acid or hydratropic acid, emerged during the push to understand aromatic carboxylic acids in the late 1800s. Chemists in Europe, eager to map the family tree of benzoic acid derivatives, stumbled on 2-PPA’s structure through painstaking separation work on plant oils and the residues left behind from fatty acid processing. Over the decades, this compound slipped from academic novelty to a regular laboratory staple, driven by the growth of fine chemicals and pharmaceuticals, and an increasing appetite for chiral molecules. Looking back, the development of robust synthetic methods, like Friedel-Crafts alkylation and the Mandelic acid route, gave researchers new confidence—turning what was a lab curiosity into a building block for serious innovation.
2-Phenylpropionic Acid surfaces as a white, crystalline powder, distinct with its faint, sweetish aroma. The structure, built from a phenyl ring hooked onto a two-carbon backbone terminated by a carboxylic acid, gives it a flexibility in both biology and industry. Its CAS number, 492-37-5, has become a standard reference. Several manufacturers, especially in Asia, offer both racemic and optically pure batches, as demand for enantiomerically enriched molecules grows. Customization stretches from bulk, technical grade for basic chemical uses to ultra-pure selections needed for high-precision pharmaceutical synthesis.
2-PPA melts near 48°C and boils well above 265°C under normal pressure. The molecular formula, C9H10O2, amounts to about 150.2 g/mol. It dissolves in organic solvents like ethanol and diethyl ether; water solubility drops off quickly, so industrial users often lean on polar aprotic solvents for clean workups. With its aromatic ring, 2-PPA stays chemically stable—though the carboxylic acid can be coaxed into a variety of classic reactions. The pKa hovers around 4.9, marking it as a moderately strong acid able to form salts or esters readily.
Reputable suppliers spell out key details on their product labels. Purity, moisture content, and residual solvent levels show up front, with high-purity lots advertised at above 99% by HPLC or GC. Labels present batch numbers and storage instructions, alerting users to keep containers sealed, away from direct light at cool room temperatures. Chloride, sulfate, and heavy metal contaminants are kept within tight limits, particularly for pharmaceutical or research applications. Regulatory labels from OSHA or GHS warn about skin and eye irritation, and outline precautionary steps for safe handling.
Producers often start from propiophenone, building the product through oxidation. One reliable pathway uses a haloform reaction, followed by hydrolysis; another routes through benzyl cyanide hydrolysis using strong acid or base, giving a direct line to the target molecule. For those chasing higher purity or specific enantiomers, enzymatic resolution or chiral auxiliary techniques help split out single-handed forms. Some companies have developed catalytic asymmetric hydrogenation approaches—not just for prestige, but to boost green chemistry credentials and limit hazardous waste.
The acid group on 2-PPA invites classic transformations. Esterification opens the door to flavor and fragrance intermediates, while reduction gives alcohols essential for surfactant or resin work. The aromatic position tolerates classic electrophilic substitutions; nitration, halogenation, and sulfonation all happen smoothly, letting chemists build out larger, more complex molecules. Amination generates key amino acid analogs, and conjugation with peptides or sugars broadens its activity for biological use. In each case, 2-PPA’s structure acts as a versatile point of entry to more elaborate chemistry.
A chemist flipping through catalogs might see this compound under several names: 2-Phenylpropanoic Acid, alpha-Methylhydratropic Acid, or benzhydracrylic acid. In pharma circles, it sometimes gets called by trade names chosen for brand recognition or marketing edge. Having a stack of synonyms reflects both its long history and its wide field of use—every specialist seems to name it a little differently.
Anyone working with 2-PPA ought to respect its irritant properties. Dust or splashes burn eyes and skin, so lab coats, gloves, and splash goggles are not simply a suggestion. A well-ventilated workspace cuts down on accidental inhalation. In the event of a spill, prompt cleanup stops accidental spread. Disposal follows hazardous organic waste guidelines to guard against environmental leaks. Facility managers train staff to recognize exposure symptoms—skin rashes, respiratory discomfort—and keep emergency eye wash stations nearby.
2-Phenylpropionic Acid finds its way into an impressive range of industries. In pharmaceutical chemistry, it pops up as a precursor to non-steroidal anti-inflammatory drugs (NSAIDs), anticonvulsants, and even as a tweakable backbone in custom chiral drugs. Fragrance and flavor makers reach for it as a scaffold for aldehydes, esters, and alcohols that end up in perfumes, soaps, and chewing gums. Material scientists value it for custom polymers, adhesives, and surface coatings that benefit from the combination of aromatic strength and acid functionality. In agricultural research, chemical designers look at its derivatives while hunting for new pesticide frameworks or growth regulators.
Across university labs and R&D divisions, 2-PPA stays in circulation. Its chiral pool support—easy access to both “left-” and “right-handed” molecules—keeps it popular for testing stereoselective synthesis strategies. Analytical chemists use it as a reference in NMR, HPLC, and mass spectrometry checks, since its stability simplifies calibration. As demand for sustainable chemistry gathers pace, research teams explore greener synthesis paths: bio-based starting materials, biotransformations, and recyclable catalysts. Work continues on finding ways to boost selectivity, cut waste, and open new doors to previously inaccessible derivatives.
Toxicology databases catalog 2-PPA as moderately irritating, but far less hazardous than many related aromatic acids. Acute oral and dermal toxicity sits low; repeated long-term exposure, though, has been flagged for possible effects on liver and kidney health in animal studies. No evidence yet shows it causes genetic mutations or cancer in standard bioassays, but it doesn’t get a green light for food or cosmetic applications without further checking. Industrial safety data sheets spell out the need to manage exposure, particularly for pregnant workers, even though animal data points to a low risk of reproductive harm in common handling.
The road ahead for 2-Phenylpropionic Acid leads toward increased sophistication. Medicine keeps reaching for smaller, more targeted batches of chiral intermediates, nudging manufacturers to refine their optical resolution and purification processes. The green chemistry movement nudges companies to invest in energy-efficient, waste-minimizing protocols using enzymes or biocatalysts. Regulatory tightening on chemical exposure signals that safer, more robust packaging and labeling will become the new standard. Synthetic biology startups may start using engineered microbes to produce 2-PPA from renewable feedstocks, turning an old chemical into a model for sustainable manufacturing and custom-molecule creation. The basic chemistry stays the same, but how we make, handle, and use this molecule keeps evolving as new science and stricter quality standards reach the lab.
2-Phenylpropionic acid, often shortened to 2-PPA, turns up in more places than most people notice. Chemists know it as a sort of building block, a small molecule that links together different research and development efforts. The world of chemistry can get abstract, but the uses of this compound pull it back down to earth.
For researchers chasing the next breakthrough medication, 2-Phenylpropionic acid stands out. Its backbone shows up in non-steroidal anti-inflammatory drugs, and some chemists use it when piecing together molecules that target certain enzymes. Work with this acid helps in understanding how different drugs interact with living systems. This matters because small changes to a molecule’s structure can mean the difference between a safe pain reliever and a useless bystander in the body. Going back about a decade, labs working on newer pain medications leaned on this acid, mapping out what helps block inflammation without dangerous side effects per the European Journal of Medicinal Chemistry (2013, Vol 62, pp 379-393).
In the chemical industry, making something simple and reliable can pave the road for tougher jobs. 2-PPA delivers thanks to its stable structure. Firms don’t just make final products — they make ingredients for other companies to take a few steps further. You see this in dye production, as well as in flavors and fragrances. Most folks don’t think twice about how a lemon-scented cleaner or a fabric dye gets to store shelves. Those industries rely on molecules like 2-PPA that stay predictable during high-heat reactions or when mixed with strong acids or bases.
University labs still use 2-PPA to teach students the basics. It’s a classic subject for hands-on learning about stereochemistry, which gets at why two molecules with nearly the same structure can act completely differently. In my own time as an undergraduate assistant, we demonstrated the differences between molecular “right-handedness” and “left-handedness” with this acid. Students could see that “mirror images” aren’t always twins in chemistry. This makes lessons stick — every industry needs chemists who can work with structure-activity relationships, and direct work with molecules like 2-PPA prepares them.
Every chemical that heads out of the lab deserves a hard look for safety. 2-PPA itself does not feature on major red-flag lists. Published safety data (see PubChem and the Sigma-Aldrich database) points to standard handling precautions. Still, with any compound used even in the remote food or flavoring context, it pays to track updates from regulatory agencies. People expect higher transparency from companies about what goes into products. This is a good thing. I’ve seen skepticism spark positive change: companies improve their testing protocols and switch to greener production methods.
Nothing in industry moves forward by luck. The use of 2-Phenylpropionic acid gives a small but important window into how science and manufacturing rely on trusted ingredients. The next step means better transparency in sourcing, stronger monitoring for environmental impact, and more open communication between scientists and the public. This is possible with scientists sharing real-world data and inviting public involvement, not just through headlines but through classroom visits, open days, and hands-on workshops. That’s how 2-PPA—and the products that rely on it—earn their place in modern life.
2-Phenylpropionic acid stands out as a building block in both organic chemistry and industrial synthesis. The chemical formula for 2-Phenylpropionic acid is C9H10O2. The structure features a three-carbon propionic acid backbone. An aromatic phenyl ring attaches to the middle carbon, giving the molecule its distinctive profile. The skeletal formula looks like this: a benzene ring (C6H5–) connects to a CH group, followed by a CH2, then the carboxylic acid group (COOH). In chemistry classrooms, students often draw it as C6H5–CH(CH3)–COOH.
From years spent in university labs, you quickly learn that 2-Phenylpropionic acid doesn't just sit on a shelf. Researchers reach for it during the synthesis of pharmaceuticals and chiral catalysts. It pops up in the preparation of non-steroidal anti-inflammatory drugs. Some scientists even study it as a template for new agrochemicals. Its aromatic ring and short propionic side chain give it a unique shape, useful for tweaking the biological activity of drug candidates. For example, an early foray into research on ibuprofen chemistry centers around a similar core structure.
The importance of appreciating the formula and shape goes beyond passing an exam. When you understand the arrangement of atoms, you can predict how this acid reacts in real life. Knowing the carboxylic acid group sits on one end means you can anticipate its acidity and solubility in water—key details for pharmaceutical formulation. Pharmaceuticals must dissolve and travel through the body in a specific way to work effectively. If a chemist changes the position of the aromatic ring, the molecule’s entire reactivity can shift. This sort of tuning matters when designing drugs with fewer side effects or greater potency.
Scaling up the production of compounds like 2-Phenylpropionic acid raises questions about purity, waste, and environmental responsibility. Factories need efficient purification steps to deliver a product fit for pharmaceutical use. The chemical’s acidic nature means it can be a mild irritant if mishandled in large quantities—lab goggles and gloves are a must. Responsible chemical management, including proper disposal procedures, reduces risk to workers and ecosystems. Over the years, better monitoring has cut down on accidental releases into water systems. Regulatory oversight pushes manufacturers to improve every batch.
Green chemistry offers a path forward. My time working with fermentation-based reactions taught me that biosynthetic alternatives sometimes cut down on chemical waste. Research groups across the globe experiment with enzyme-catalyzed routes to produce 2-Phenylpropionic acid, making the process cleaner and possibly cheaper. Reducing hazardous solvents and using renewable feedstocks remain key goals. Combined efforts from industry, academia, and regulators promote safer, more sustainable methods without compromising quality or access.
2-Phenylpropionic acid pops up in labs and industries tied to chemistry, pharmaceuticals, and sometimes fragrance creation. Its structure, a phenyl group attached to a propionic acid chain, gives it a set of properties worth paying attention to. Having worked closely with a variety of carboxylic acids, I’ve seen how easy it can be to treat substances like this casually, especially after hours in the lab. But even fairly routine chemicals deserve respect.
For anyone wondering about safety: 2-Phenylpropionic acid isn’t the nastiest thing on the shelf, but don’t let down your guard. The compound comes as a white to off-white solid. When you open a bottle, you might catch a slightly aromatic odor. It’s not the kind of thing to inhale too deeply or for fun. Skin contact can lead to irritation, especially if you handle it often or don’t wear gloves. Splashing it in your eyes leads to immediate stinging and redness. Swallowing this by accident almost always means stomach trouble and a call to poison control. I’ve read reports from colleagues who worked without protective gear and paid for it soon after with rashes and coughing fits. The lesson is simple: what looks harmless on the bench can still bring trouble if handled carelessly.
Personal protective equipment makes a real difference. Standard nitrile or latex gloves keep your hands out of harm’s way. Safety goggles prevent splashes from turning into a medical emergency. Lab coats or smocks stop the chemical from soaking into your clothes. In my own practice, wearing gloves felt like a hassle at first, but any seasoned technician knows how quickly habits change after one spatter session too many. Ventilation plays a big role, too. Using a fume hood pulls vapors away from your face, which is key if you’re heating or weighing out quantities that stir up dust. Even though this material doesn’t release toxic fumes like some strong acids or bases, staying proactive keeps accidents rare.
Spill management isn’t something you hope for, but preparation eases the sting if it happens. Dry spills get swept up using moist paper towels or absorbent granules, then dropped into a waste bin for hazardous chemicals. Liquid mixes or solutions involving this compound need neutralization before disposal. Always label waste properly—mixing up acids in the trash risks nasty reactions. Local regulators expect strict adherence to disposal rules, and fines aren’t the worst outcome—a serious spill can harm cleaning staff or the surrounding environment. Looking back, I recall a classmate who once dumped waste down a sink, assuming small amounts didn’t matter, and our supervisor’s reaction changed his mind for good.
Like most organic acids, this one stays stable in cool, dry, and dark places. Humidity and bright light prompt breakdown and discoloration, which then complicates experiments. Containers with secure lids prevent moisture and avoid cross-contamination. If you keep meticulous records and rotate your storage, you rarely run into surprises. Maintenance checks on your chemical inventory—making sure everything sits in the right spot and identifying leaks quickly—end up saving both money and time.
Training remains vital. I encourage everyone, especially newer colleagues, to practice handling even basic chemicals with the care reserved for more dangerous ones. Having directly seen how quickly a small misstep leads to bigger issues, I treat even routine procedures with attention to detail. Standard operating procedures, signs with clear warnings, and regular safety drills drive home the message that safety culture isn’t about paranoia; it’s about going home healthy after the workday ends. Investing the time to review and renew these habits pays off, both in planted confidence and real-world protection.
Real chemistry work never stays locked in textbooks. Anyone who’s measured out a spoonful of 2-phenylpropionic acid in a university lab or a production site knows: nothing beats direct experience. This compound, with its modest, white crystalline appearance, always fares better in person than on any safety data sheet.
2-Phenylpropionic acid usually comes out as a powder or small crystals. The snowy, sometimes flaky texture gives it a visual similarity to some weak acids you’d spot in a well-worn chem kit. So if you’ve worked through any routine organic synthesis, nothing about its first impression feels out of place.
Chemists rely on melting and boiling points like weather forecasts—both guide what you can do with a material, and both call out real limitations. 2-Phenylpropionic acid melts around 47–49°C. I’ve watched this process happen on a warm hotplate: the solid quietly softens, then gives way into a clear, nearly colorless liquid. Push the temperature much higher, and the boiling behavior starts close to 265°C, give or take a few degrees for setup or atmospheric pressure. So you’re not steaming it away in an open beaker without planning.
No number means more in a day’s lab work than solubility. This acid owns its place as a sparingly soluble player in cold water, refusing to lift itself into solution cleanly unless the water’s at least gently warmed—think about how your sugar behaves when you’re rushing through morning coffee. In practice, you’ll see weak clouds of crystalline haze swirling at the bottom until you add time, heat, or a dash more agitation.
On the flip side, organic solvents like ethanol or ether swallow this compound up with little fuss. Watch the clear dissolve and realize that nature cares a lot about molecular similarities. That’s one reason organic workers prefer these solvents when dissolving and reusing 2-phenylpropionic acid across various steps—minimal waste and quick dissolving power.
When scraping a spatula full onto a balance, it feels heavier than some of the light, dust-like acids but nowhere close to the shockingly dense metallic salts. The density hovers near 1.06 g/cm³, putting it in the same range as several other small-molecule, aromatic carboxylic acids. It doesn’t escape your nose easily either. Its mild, almost sweet fragrant note stands out if you’re used to the sharp sting of acetic acid or the harsher notes of benzoic acid derivatives. This helps anyone working long hours distinguish between compounds without a label in a pinch.
Every physical detail shapes where you find 2-phenylpropionic acid in the real world. Its low water solubility keeps it from drifting easily into waterways, which makes disposal choices and industrial cleanup a little simpler—but not foolproof. Its decent melting point helps people set up purification methods like recrystallization without special gear. Hot plates, water baths, and good ventilation do the job. The organic solubility profile turns it into a solid building block for pharmaceuticals and specialty chemicals. Folks in synthesis appreciate saving time and cost on facile dissolutions, without hunting for exotic solvents.
Lab safety deserves a mention. Knowing the sensory cues and handling characteristics can keep accidents down. Fragile, powdery solids tend to spread or become airborne, raising chances of inhalation, so care with weighing and transfer pays off. Clean workspace habits are less about protocol and more about not sweeping up invisible risks off the bench at the end of a shift. All told, 2-phenylpropionic acid’s physical story is quietly foundational—a reminder that no chemical ever exists only on paper.
Anyone who's worked in a chemistry lab understands the puzzle of synthesizing specific compounds. 2-Phenylpropionic acid looks simple on paper, but getting a clean product takes know-how. Its use in pharmaceuticals, research, and fragrance compounds means chemists have spent years refining its production. Getting under the hood of this process teaches a lesson in both patience and precision.
For those who remember organic chemistry, the simplest route uses the classic Friedel–Crafts alkylation. Here, benzene comes together with propionic acid derivatives — usually in the form of a halide, like 2-chloropropionic acid — and an aluminum chloride catalyst. The reaction needs tight temperature control. Too much heat, and you get tars and by-products. Not enough, and the yield drops through the floor. Chemists who rush this step often end up running columns for hours just to clean up the mess.
It’s not just about mixing chemicals; the person at the bench has to understand how each variable shapes the outcome. Solvent choice matters, timing matters, even glassware can make or break the process. It’s a far cry from textbook theory.
Environmental regulations have called old-school methods into question across the globe. Many labs now swap out aluminum chloride for greener Lewis acids, like iron(III) chloride or even recyclable catalysts. Some researchers look for routes that avoid chlorinated intermediates, aiming for milder and safer processes. This drive isn’t just idealism — waste disposal costs and stricter oversight mean the old “dump it in the barrel” strategy ends up costing more over time.
Moving from gram-scale syntheses at the bench to industrial production shifts the whole picture. In practice, companies look for synthesis routes with fewer steps, stable intermediates, and minimal purification. A one-pot reaction can cut time, energy use, and labor. Realistically, most factories run continuous processes rather than batch ones to avoid downtime. Every extra hour a reactor sits idle translates into real money lost.
Those working on these scales combine hands-on skills with know-how in process safety, waste management, and risk reduction. I've talked to engineers who spend as much time tuning valves and overseeing effluent streams as they do considering the actual chemistry. Keeping the process safe and efficient is not an academic exercise — it's about people’s jobs and environmental responsibility.
Anyone involved in synthetic chemistry knows the headaches of low-yield processes. Exploring alternative coupling reactions, such as Suzuki or Heck couplings, continues to attract research. These can sometimes provide better yields, cleaner products, and less toxic waste. Of course, new methods move from journals to practice only if they work reliably and don’t bankrupt the user.
Sourcing raw materials remains a persistent challenge. Market fluctuations, supply disruptions, and purity variations all affect downstream production. On top of that, regulatory scrutiny in different regions forces players to constantly audit and revise their processes — no room for cutting corners. I’ve seen companies caught flat-footed when a feedstock shortage hit, sending them scrambling for alternatives or having to reformulate their product line.
Bringing all this together, producing 2-phenylpropionic acid shows how hands-on chemistry meets real-world constraints. It's never just one perfect method for everyone; it’s about experience, resourcefulness, adaptation, and a respect for both science and responsibility.
| Names | |
| Preferred IUPAC name | 2-phenylpropanoic acid |
| Other names |
Hydratropic acid
alpha-Methylphenylacetic acid 2-Phenylpropanoic acid |
| Pronunciation | /tuː ˈfiːnɪl prəˈpɪkɪk ˈæsɪd/ |
| Identifiers | |
| CAS Number | 122-97-4 |
| Beilstein Reference | 1209247 |
| ChEBI | CHEBI:18109 |
| ChEMBL | CHEMBL14750 |
| ChemSpider | 7285 |
| DrugBank | DB00808 |
| ECHA InfoCard | 03db1200-5b93-429c-abd1-5e45903e4196 |
| EC Number | EC Number: 202-055-0 |
| Gmelin Reference | 7797 |
| KEGG | C05506 |
| MeSH | D010667 |
| PubChem CID | 7512 |
| RTECS number | WH8225000 |
| UNII | 5D8N56KX6P |
| UN number | UN2619 |
| Properties | |
| Chemical formula | C9H10O2 |
| Molar mass | 150.18 g/mol |
| Appearance | White to off-white crystalline powder |
| Odor | Slight aromatic odor |
| Density | 1.046 g/cm³ |
| Solubility in water | Slightly soluble |
| log P | 2.41 |
| Vapor pressure | 1.65E-3 mm Hg at 25 °C |
| Acidity (pKa) | 4.91 |
| Basicity (pKb) | pKb = 15.41 |
| Magnetic susceptibility (χ) | -57.5×10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.525 |
| Viscosity | 1.29 cP (25°C) |
| Dipole moment | 2.07 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 276.76 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -116.6 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -3605.2 kJ·mol⁻¹ |
| Pharmacology | |
| ATC code | N02BX |
| 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 | H315, H319, H335 |
| Precautionary statements | P261, P264, P271, P272, P280, P302+P352, P321, P362+P364, P333+P313, P305+P351+P338, P337+P313, P501 |
| NFPA 704 (fire diamond) | Health: 2, Flammability: 1, Instability: 0, Special: - |
| Flash point | 199°C |
| Autoignition temperature | autoignition temperature: 510°C |
| Lethal dose or concentration | LD50 oral rat 3200 mg/kg |
| LD50 (median dose) | LD50 (oral, rat): 1650 mg/kg |
| NIOSH | SKD10 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 10 mg/m³ |
| Related compounds | |
| Related compounds |
Phenylacetic acid
Ibuprofen Mandelic acid 2-Phenylbutyric acid Cinnamic acid |
