{"id":3918,"date":"2025-09-11T00:46:50","date_gmt":"2025-09-11T00:46:50","guid":{"rendered":"https:\/\/modafinil.pl\/?post_type=product&p=3918"},"modified":"2026-10-03T06:13:10","modified_gmt":"2026-10-03T06:13:10","slug":"paracetamol","status":"publish","type":"product","link":"https:\/\/modafinil.pl\/en\/sklep\/paracetamol\/","title":{"rendered":"Paracetamol (CAS 103-90-2) \u2014 Chemical Reagent 1000 mg, Purity \u2265 99.0%"},"content":{"rendered":"

N-(4-hydroxyphenyl)acetamide<\/strong>, crystalline powder, 1000 mg package. Material intended exclusively for in vitro laboratory and analytical research<\/strong>. The product is not intended for human or animal consumption<\/strong>, and is not a medicinal product, dietary supplement, food, or cosmetic.<\/p>\n

Three Different Entities That Must Not Be Confused<\/h2>\n

For this molecule, separating the layers matters more than usual, because unlike most entries in our catalog, the corresponding medicinal product is one of the most widely used over-the-counter medicines in the world. The widespread availability of the pharmaceutical preparation does not transfer<\/strong> to the status of the reagent offered here \u2014 these are two separate legal entities, regardless of how readily available the former is:<\/p>\n\n\n\n\n\n\n\n
Separating the layers: substance \u2014 medicinal product \u2014 reagent<\/caption>\n
Entity<\/th>\nWhat It Is<\/th>\nStatus<\/th>\n<\/tr>\n<\/thead>\n
Chemical substance
paracetamol \/ acetaminophen, CAS 103-90-2<\/th>\n		A chemical concept \u2014 a molecule with a defined structure. On its own it is neither a drug nor a reagent; its status is conferred by the form in which it is manufactured and placed on the market.<\/td>\n\u2014<\/td>\n<\/tr>\n
Medicinal product
e.g. Apap, Acenol, Panadol, Codipar, Efferalgan<\/th>\n		A pharmaceutical preparation: a defined pharmaceutical form, manufacturing under GMP conditions, registration documentation, safety surveillance. In Poland available both over the counter (selected oral forms) and on prescription (including intravenous forms).<\/td>\nclinical trials in humans concern this entity<\/strong><\/td>\n<\/tr>\n
Chemical reagent
the material offered here<\/th>\n		Material for laboratory and analytical work. It does not hold, and cannot hold, approval for use in humans or animals<\/strong> \u2014 it has no pharmaceutical form and no medicinal product documentation, regardless of the fact that the same molecule in a different form is a drug sold over the counter in every pharmacy.<\/td>\nanalytics, chemistry, reference standards<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The consequence is unambiguous.<\/strong> The data referenced further down this page come either from chemical and analytical research on the molecule itself<\/strong> (crystal structure, stability, determination methods), or from toxicity-mechanism research conducted on animal models and in vitro<\/strong>. The one human clinical study cited below concerns exclusively the registered medicinal product<\/strong>, never the analytical reagent. None of this information transfers to the material offered here<\/strong>, and none of it is a basis for using it outside the laboratory. The reagent is not the form in which the substance is administered to humans, and cannot be used that way \u2014 the widespread availability of the pharmacy preparation does not change this.<\/p>\n

Reagent Identification Card<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Registration data and identifiers \u2014 paracetamol<\/caption>\n
Systematic name (IUPAC)<\/th>\nN-(4-hydroxyphenyl)acetamide<\/td>\n<\/tr>\n
Common name<\/th>\nparacetamol (Europe), acetaminophen (North America, Japan)<\/td>\n<\/tr>\n
CAS number<\/th>\n103-90-2<\/td>\n<\/tr>\n
Molecular formula<\/th>\nC8<\/sub>H9<\/sub>NO2<\/sub><\/td>\n<\/tr>\n
Molar mass<\/th>\n151.16 g\u00b7mol\u22121<\/sup><\/td>\n<\/tr>\n
Monoisotopic mass<\/th>\n151.0633 Da<\/td>\n<\/tr>\n
InChIKey<\/th>\nRZVAJINKPMORJF-UHFFFAOYSA-N<\/td>\n<\/tr>\n
SMILES<\/th>\nCC(=O)NC1=CC=C(C=C1)O<\/td>\n<\/tr>\n
PubChem CID<\/th>\n1983<\/a><\/td>\n<\/tr>\n
Form<\/th>\ncrystalline powder, white to almost white<\/td>\n<\/tr>\n
Melting point<\/th>\n169.8 \u00b0C (PubChem reference value); the exact melting point and HPLC purity of a given batch are stated on the certificate of analysis enclosed with the shipment<\/td>\n<\/tr>\n
Purity<\/th>\n\u2265 99.0%<\/td>\n<\/tr>\n
Intended use<\/th>\nresearch reagent \u2014 not for human or animal consumption<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Lineage of the Molecule: From Acetanilide to Paracetamol<\/h2>\n

Paracetamol is not a molecule designed from scratch for analgesic action \u2014 it is a purified metabolite<\/strong> of two earlier compounds that proved too toxic to remain in use. The history of this family dates back to the late 19th century and is well documented in the literature on the history of pharmacology [1<\/a>].<\/p>\n

The Shadow of Acetanilide and Phenacetin<\/h3>\n

The starting compound was acetanilide<\/strong>, introduced into medicine in the 1880s and quickly withdrawn because of methemoglobinemia. Its successor was phenacetin<\/strong> \u2014 an ether derivative considered safer and widely used throughout most of the 20th century, until it was withdrawn in one country after another because of nephrotoxicity and suspected carcinogenicity associated with long-term use.<\/p>\n

Discovery of the True Carrier of Activity<\/h3>\n

Critical to paracetamol\u2019s present-day status was the mid-20th-century finding that it \u2014 not phenacetin or acetanilide \u2014 is the main active metabolite<\/strong> responsible for the analgesic and antipyretic action of this family of compounds, with substantially lower toxicity than the parent compounds. This precursor\u2013metabolite relationship is analogous to the one described in our catalog for the modafinil<\/a>\/adrafinil pair \u2014 with the difference that, in paracetamol\u2019s case, it was the metabolite, not the precursor, that became the independently registered compound placed on the market in the late 1950s.<\/p>\n

Timeline<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
Timeline: from acetanilide to current regulatory status<\/caption>\n
1886<\/th>\nintroduction of acetanilide into medicine; rapid withdrawal because of methemoglobinemia<\/td>\n<\/tr>\n
1887\u20131893<\/th>\nintroduction of phenacetin as the successor to acetanilide; decades of widespread use<\/td>\n<\/tr>\n
1878<\/th>\nfirst documented synthesis of paracetamol (Morse), outside the mainstream of pharmacology at the time<\/td>\n<\/tr>\n
mid-20th century<\/th>\nidentification of paracetamol as the main active metabolite of phenacetin\/acetanilide, with lower toxicity [1<\/a>]<\/td>\n<\/tr>\n
1950s\u20131960s<\/th>\nregistration as an independent medicinal product in the United States and Europe; gradual withdrawal of phenacetin<\/td>\n<\/tr>\n
2000<\/th>\nresolution of the crystal structure of the polymorphic form under high pressure [2<\/a>]<\/td>\n<\/tr>\n
2011<\/th>\ndetermination method in plasma and urine by isotope-labeled GC-MS [6<\/a>]<\/td>\n<\/tr>\n
2020<\/th>\ndescription of a new, elusive crystal form in the Journal of the American Chemical Society<\/em> [3<\/a>]<\/td>\n<\/tr>\n
2021<\/th>\nmethodological recommendations for the hepatotoxicity model in laboratory animals [12<\/a>]<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Chemistry: The Amide Bond, Polymorphism, and What They Mean for the Laboratory<\/h2>\n

Why the Amide Bond Determines Stability<\/h3>\n

The paracetamol molecule is a phenol ring substituted with a hydroxyl group in the para<\/em> position relative to the acetamide group. It is precisely the amide bond<\/strong> that is susceptible to hydrolysis: under strongly acidic or basic conditions, and under elevated temperature, it breaks down into p<\/em>-aminophenol and acetic acid. The kinetics of this degradation \u2014 including identification of the products by HPLC coupled with electrospray ionization \u2014 were described by Gilpin and Zhou [4<\/a>], and the effect of time and temperature on the observed color changes of the solution \u2014 as an indicator of progressing degradation \u2014 by Mochizuki and Takayama [5<\/a>]. For the laboratory this has a practical consequence: stock solutions should be prepared fresh and prolonged storage under elevated temperature or extreme pH should be avoided.<\/p>\n

Two Crystal Forms, Two Behaviors<\/h3>\n

Paracetamol crystallizes in more than one polymorphic form \u2014 the most common, monoclinic form is the thermodynamically stable form under ambient conditions, but under high hydrostatic pressure it undergoes anisotropic distortion of the crystal lattice, as described by Boldyreva and co-workers using X-ray diffraction [2<\/a>]. The existence of harder-to-obtain, less stable crystal forms \u2014 including forms previously considered impossible to isolate \u2014 was recently confirmed by Liu, Gabriele, and Davey in the Journal of the American Chemical Society<\/em> [3<\/a>]. For analytical practice this means that identifying the compound by melting point or simple powder diffraction alone does not always settle which polymorphic form is present \u2014 and different forms can differ in solubility and dissolution rate.<\/p>\n

Physicochemical Characterization<\/h3>\n\n\n\n\n\n\n\n\n\n\n
Computed descriptors and their analytical significance<\/caption>\n
Parameter<\/th>\nValue<\/th>\nSignificance<\/th>\n<\/tr>\n<\/thead>\n
Partition coefficient (XLogP)<\/th>\n0.5<\/td>\nlow lipophilicity \u2014 elutes early in an RP-HPLC gradient, requires careful mobile-phase selection when analyzed in mixtures with more lipophilic analgesics<\/td>\n<\/tr>\n
Topological polar surface area<\/th>\n49.3 \u00c52<\/sup><\/td>\nmoderate; the hydroxyl and amide groups are active in infrared and NMR<\/td>\n<\/tr>\n
Hydrogen bond donors<\/th>\n2<\/td>\nthe phenolic OH group and the amide N\u2013H<\/td>\n<\/tr>\n
Hydrogen bond acceptors<\/th>\n2<\/td>\nthe phenolic and carbonyl oxygens<\/td>\n<\/tr>\n
Rotatable bonds<\/th>\n1<\/td>\nthe molecule is nearly planar, with limited conformational freedom<\/td>\n<\/tr>\n
Solubility<\/th>\ngood in ethanol, methanol, DMSO, and DMF; poor in water and nonpolar solvents<\/td>\nprepare stock solutions in a polar protic or aprotic solvent, not in water<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Why One Molecule Has Several Systematic Names<\/h2>\n

In the chemical and pharmacopoeial literature, the same substance with CAS number 103-90-2 appears under several names, depending on region and context \u2014 none of them is a trade name of a medicinal preparation<\/strong>; all of them refer to the molecule itself:<\/p>\n