CAS No. 103-90-2 Chemical Name: Acetaminophen Synonyms PARACETAMOL;APAP;4-ACETAMIDOPHENOL;N-(4-HYDROXYPHENYL)ACETAMIDE;PARACETAMOL POWDER;Panadol;Acetaminofen;PARACETAMOL DC96;TYLENOL;excedrin CBNumber: CB1413658 Molecular Formula: C8H9NO2
Lewis structure
| Melting point | 168-172 °C(lit.) |
|---|---|
| Boiling point | 273.17°C (rough estimate) |
| Density | 1,293 g/cm 3 |
| vapor pressure | 0.008Pa at 25℃ |
| refractive index | 1.5810 (rough estimate) |
| Flash point | 11 °C |
| storage temp. | Inert atmosphere,Room Temperature |
| solubility | ethanol: soluble0.5M, clear, colorless |
| pka | 9.86±0.13(Predicted) |
| form | Crystals or Crystalline Powder |
| color | White |
| PH | 5.5-6.5 (H2O, 20℃)(saturated solution) |
| PH Range | 5.5 - 6.5 (H?O, 20 °C) (saturated solution) |
| Odor | odorless |
| explosive limit | 15%(V) |
| Water Solubility | 14 g/L (20 ºC) |
| Merck | 14,47 |
| BRN | 2208089 |
| BCS Class | 3,4 |
| InChIKey | RZVAJINKPMORJF-UHFFFAOYSA-N |
| LogP | 1.098 at 25℃ |
| CAS DataBase Reference | 103-90-2(CAS DataBase Reference) |
| EWG's Food Scores | 1 |
| NCI Dictionary of Cancer Terms | acetaminophen |
| FDA UNII | 362O9ITL9D |
| NCI Drug Dictionary | acetaminophen |
| ATC code | N02BE01 |
| NIST Chemistry Reference | Acetaminophen(103-90-2) |
| IARC | 3 (Vol. 50, 73) 1999 |
| EPA Substance Registry System | Acetaminophen (103-90-2) |
| Manufacturer | Product number | Product description | CAS number | Packaging | Price | Updated | Buy |
|---|---|---|---|---|---|---|---|
| Sigma-Aldrich | A3035 | Acetaminophen analytical standard | 103-90-2 | 1vial | $145 | 2024-03-01 | Buy |
| Sigma-Aldrich | A3035 | Acetaminophen analytical standard | 103-90-2 | 5vials | $528 | 2024-03-01 | Buy |
| Sigma-Aldrich | 8.22325 | 4′-Hydroxyacetanilide for synthesis | 103-90-2 | 250g | $49.1 | 2024-03-01 | Buy |
| Sigma-Aldrich | A-064 | Acetaminophen solution 1.0?mg/mL in methanol, ampule of 1?mL, certified reference material, Cerilliant? | 103-90-2 | 1mL | $36.6 | 2024-03-01 | Buy |
| Sigma-Aldrich | 8.22325 | 4′-Hydroxyacetanilide for synthesis | 103-90-2 | 1kg | $164 | 2024-03-01 | Buy |
| Product number | Packaging | Price | Buy |
|---|---|---|---|
| A3035 | 1vial | $145 | Buy |
| A3035 | 5vials | $528 | Buy |
| 8.22325 | 250g | $49.1 | Buy |
| A-064 | 1mL | $36.6 | Buy |
| 8.22325 | 1kg | $164 | Buy |
The chemiacal name of Acetaminophen is N-(4-hydroxy phenyl) acetamide and the trade name is paracetamol belonging to acetanilide antipyretic analgesics. It was first synthesized by Morse in 1878 and first used in clinic by VonMering in 1893. It has become an over the counter drug in the USA since 1955 and our country started production at the end of the 1950’s. Acetaminophen is a white crystalline or a crystalline powder in appearance with melting point from 168℃ to 172℃, odorless, slightly bitter taste, freely soluble in hot water or ethanol, dissolved in acetone, practically insoluble in cold water and petroleum ether. It is stable below 45℃ but will be hydrolyzed into p-aminophenol when exposed to humid air, then oxidized further. The color grades gradually from pink to brown then to black, so it should be sealed and stored in a cool and dry place.Acetaminophen has the antipyretic activity by inhibiting the synthesis of hypothalamic thermoregulation prostaglandins and its strength of antipyretic effect is similar to aspirin. On the other hand, Acetaminophen can produce analgesic effect by inhibiting the synthesis of prostaglandins in the central nervous system and blocking impulses of nociceptive nerve endings, but weaker than aspirin. Compared with aspirin, Acetaminophen has minor irritation, few allergic reactions and other advantages. Its antipyretic and analgesic effect is similar to phenacetin, and the use of Acetaminophen increases due to limiting or banning using phenacetin in many countries.In clinical, it is mainly used for fever and headache caused by cold and relieving mild to moderate pain such as joint pain, muscle pain, neuralgia, migraine, dysmenorrhea, cancer pain, postoperative analgesia and so on. It can be used for patients who are allergic to aspirin, intolerant of aspirin, or unsuited for aspirin, such as patients with varicella, hemophilia and other hemorrhagic disease (patients having anticoagulant therapy included), as well as patients with slight peptic ulcer and gastritis. In addition, it also can be used for the synthesis of benorylate and used as asymmetric synthetic intermediates, photographic chemicals and stabilizer of hydrogen peroxide.
Obtain prism crystallization from ethanol. Melting point 169-171℃, relative density 1.293(21/4℃). Soluble in ethanol, acetone and hot water, difficult to dissolve in water, insoluble in petroleum ether and benzene. Odorless, bitter. The pH value of saturated aqueous solution is 5.5-6.5.
Acetaminophen is used as antipyretic analgesics. It has the antipyretic activity by means of mediated peripheral vasodilation and perspiration caused by inhibiting the cyclooxygenase which selectively inhibiting the synthesis of hypothalamic thermoregulation prostaglandins, and its strength of antipyretic effect is similar to aspirin. As a peripheral analgesic, it can produce analgesic effect by inhibiting the synthesis and release of prostaglandins and increasing pain threshold. However, its action is weaker than aspirin and it is only effective for mild to moderate pain. There is no obvious anti-inflammation effect.
The oral absorption is rapid and complete, and the peak time occurs 0.5～2h later. The plasma protein binding rate is 25%～50%. This product is equally distributed in the body, 90%～95% is metabolized in the liver and mainly excreted from the kidney combining with glucuronic acid and about 3% exits the body unchanged in the urine within 24h. Its half-life (t1/2) is 1～4h (average 2h). In case of renal insufficiency t1/2 is not affected, but t1/2 of patients with hepatic insufficiency, newborns or elderly patients may increase and t1/2 of children may decrease. It can be secreted by milk.
1. Using nitrobenzene as raw material
In the presence of concentrated sulfuric acid and sixteen alkyl methyl ammonium chloride, nitrobenzene is transformed into p-Aminophenol by catalytic hydrogenation with Pd/C as catalyst. P-acetaminophen is synthesized acetylation by one-step acylation without separation and the yield is 64.3%. The reaction is as followed: 
2. Using paranitrophenol as raw material
With paracetamol as raw material and Pd/C as catalyst, paracetamol is synthesized by hydroacylation on one-step method. The optimum solvent is acetic acid of which the dosage is 2 to 5 times of paranitrophenol and the yield of paracetamol is up to 95%. When Pd-La/C is used as catalyst instead, the yield can reach 97%. The reaction is as followed: 
3. Using p-aminophenol as raw material
Under these conditions of using p-aminophenol and acetic anhydride as raw materials, zinc powder as the antioxidant, activated carbon as the decolorizing agent and dilute acetic acid as the reaction medium, paracetamol is synthesized by microwave irradiation technology and the yield is up to81.2%. The reaction is as followed: 
4. Using p-Hydroxyacetophenone as raw material
First oximate p-Hydroxyacetophenone and then rearrange it to obtain paracetamol by means of Beckmann. Under this method, the yield of 4-hydroxyacetophenone oxime obtained by oximating p-Hydroxyacetophenone is 93.5%. Then we use Hβ molecular sieve as catalyst and acetone as the solvent to obtain acetaminophen by rearrangement and the yield is 81.2 %. In the rearrangement reaction, acetone is used as the solvent and Al-MCM-41 molecular sieve is used as the catalyst. The yield is the highest when the content of phosphoric acid in the catalyst is 30%. The reaction is as followed: 
5. Using phenol as raw material
Phenol is used as the raw material and synthesizes paracetamol after acetylation, Fries rearrangement, oxime and Beckmann rearrangement. The yields are 82%, 68.6%, 50.5%,
respectively. The reaction is as followed: 
Usage
This product is antipyretic and analgesic whose international nonproprietary name is Paracetamol. It is the most common non anti-inflammatory analgesia-antipyretic drugs without anti inflammatory and anti rheumatism action. Its antipyretic effect is similar to aspirin, but analgesic effect is weak. It is the best of breed of acetanilid drugs. The product is especially suitable for patients who cannot use carboxylic acids drugs. It is used for cold and toothache. Acetaminophen is also used as organic synthesis intermediates, stabilizer of hydrogen peroxide, photographic chemicals.
Dosage
1. Oral (1) Paracetamol tablets or paracetamol capsules: adults take 300～600mg at a time and 3～4 times a day according to the need. The daily dosage should not be greater than 2g. Defervescence treatment is generally less than 3 days and the administration of pain relief lasts less than 10 days. Children take 10～15mg/kg every 4～ 6 hours. The dosage of children under the age of 12 does not exceed 5 times a day, a five-day course at most. This product should not be taken for a long time.
2. Dispersible tablets: When take tablets, disperse them in warm water dispersion. The commonly used amount of children is 10～15mg/kg every 4～ 6 hours. The dosage of children under the age of 12 does not exceed 5 times a day, a five-day course at most. Children under 3 years old cut back on the amount.
1. Allergic reactions: This product has less and slight side effects a dose treatment except for occasional rashes, hives and other allergic reactions. Methemoglobinemia may occur in a few cases.
2. Hepatorenal damage: A large number of long-term use, hepatorenal damages and thrombocytopenia may occur, even jaundice, oliguria, acute severe hepatitis, which could lead to coma, and death. Using at high dosage may cause nausea, vomiting, stomach pain, stomach cramps, diarrhea, anorexia, sweating, etc.
3. For children under the age of 3, the development of liver and kidney function is not mature with poor detoxification and excretory function, so they should try to avoid using this product. In addition, patients with liver and kidney insufficiency and pregnant women should use cautiously. The long-term drug users should regularly check renal function and hemogram.
It is contraindicated in patients allergic to the product and patients with severe liver and kidney function deficiency.
Organic synthesis intermediates, stabilizer of hydrogen peroxide, photographic chemicals, non anti-inflammatory analgesia-antipyretic drugs.
Produced by acetylation of p-aminophenol.
Method 1: add p-aminophenol into dilute acetic acid, then add glacial acetic acid, heat up to 150℃and react for 7h, add acetic anhydride and react for 2h, check the end point and cool to 25℃ after the acceptance, shake it and filter, water until no acetic acid flavor exists, dry to get crude products.
Method 2: distill p-aminophenol, acetic acid and acid industrial containing more than 50% acid together, the speed of distilling dilute acid for is 1/10 of the total distillate in one hour, check the residue of p-aminophenol less than 2.5% aminophenol by sampling inspection when inner temperature rises up to 130℃, add dilute acid (content of more than 50%), cool to get crystallization. After shaking and filter, first use a small amount of dilute acid to wash, and then use a large number of water till filtrate is near colourless to get crude products. The yield of method 1 is 90%, but the yield of method 2 is 90-95%. Refining methods: add the crude product when the water is heated to near boiling. Heat up to the total dissolution, add activated carbon soaked in water, use dilute acetic acid to adjust till pH=4.2-4.6, boil for 10min. Filter press, add a small amount of sodium bisulfite into the filtrate. Cool to below 20℃, separate crystals out. After shaking and filter, wash and dry to get active ingredients, paracetamol finished products.
Other methods of production are as followed:
(1) p-nitrophenol is reduced by zinc in acetic acid, and acetaminophen is obtained by acetylation at the same time;
(2) put the hydrazone generated from p-hydroxyacetophenone in acid solution containing sulfuric acid, and then add sodium nitrite to get acetaminophen by renversement.
Acetaminophen is an analgesic and antipyretic compound. Unlike many NSAIDs, which inhibit both COX-1 and COX-2, early studies suggested that acetaminophen is a poor inhibitor of both isoforms. However, it does inhibit COX-2 by 83% and COX-1 by 56% in human blood ex vivo, albeit at a high 1,000 mg dose, with IC50 values of 25.8 and 113.7 μM, respectively. Acetaminophen is enzymatically and non-enzymatically converted to several reactive metabolites that contribute to adverse or indirect effects, including liver injury. At toxic doses, the acetaminophen metabolite N-acetyl-4-benzoquinone imine (NAPQI; ) depletes glutathione reserves in the liver, leading to an accumulation of NAPQI and subsequent hepatocyte necrosis. Acetaminophen decreases glutathione levels and reduces glutathione peroxidase activity in mice when administered at a dose of 250 mg/kg and induces ferroptotic cell death in primary mouse hepatocytes, an effect that can be blocked by the ferroptosis inhibitor ferrostatin-1 . Acetaminophen has analgesic and antipyretic properties in animal models.
Acetaminophen differs from the nonsteroidal anti-inflammatory agents described in that it is devoid of anti-inflammatory and antirheumatic properties. It was recently shown that acetaminophen, like aspirin, inhibits cyclooxygenase action in the brain and is even stronger than aspirin. On the other hand, the mechanism of analgesic action of acetaminophen is not fully clear, since it acts poorly on peripheral cyclooxygenase.
Trigesic ,Squibb ,US ,1950
