Acetaminophen, also known as paracetamol is a medicine used for mild pain relief. It has the chemical formula C8H9NO2, extended formula HOC6H4NHCOCH3, and IUPAC chemical name N-(4-hydroxyphenyl)acetamide. The “N” is a position indicator for the phenyl ring which is a benzene (C6H6) derivative. The 4 signifies the hydroxyl group (OH) is at the fourth location of the phenyl group. Acetamide (C2H5NO or CH3CONH2) is the base component for the molecule, and its nitrogen attaches to the phenyl ring. Acetaminophen is a white crystalline solid with a density of 1.293 g/mL, molar mass of 151.165 g/mol, melting point of 168 C, and boiling point of 420 C. The molecule has planar geometry and two hydrogen bonds, and its 7 carbons have sp2 hybridization. It is a member of the class of phenols, containing a hydroxyl group bonded to an aromatic hydrocarbon ring, and specifically the 4-aminophenols, meaning an acetyl group (COCH3) replaced a hydrogen in the amino group. It can be synthesized through the acetylation of 4-aminophenol with acetic acid and acetic anhydride at a high temperature. Alternatively, it can be made with acetic anhydride in pyridine or acetyl chloride and pyridine in methylbenzene. Acetaminophen is on the World Health Organization's List of Essential Medicines. It works by inhibiting the composition of chemical messengers called prostaglandins which help send pain signals and start fevers, so it has analgesic (pain reliever) and antipyretic (fever reducer) properties.

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