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How acetaminophen is made

Acetaminophen plants reach one intermediate, 4-aminophenol, then bolt on an acetyl group in the last reaction.

stations
6
things upstream
16
raw sources
5
steps from the ground
6

The short version

Acetaminophen, also called paracetamol, comes from chemical plants that start with a nitrated aromatic such as p-nitrophenol. Hydrogen reduces that to 4-aminophenol, and acetic anhydride adds an acetyl group to make the crude drug. Charcoal strips the color, repeated crystallization and centrifuging purify it, and the crystals are dried, ground and packed for tablet and syrup makers.

  1. Prepare the nitro compound

    A classical route treats phenol with nitric acid. One plant design in an Intratec report starts instead from 4-nitrochlorobenzene and caustic soda in an autoclave. The product, p-nitrophenol, is purified by crystallizing and centrifuging.

    Goes in
    PhenolNitric acid

  2. Reduce it with hydrogen

    Hydrogen gas and the nitro compound meet in a reactor over a metal catalyst, giving 4-aminophenol. The mixture is cooled and filtered to recover the catalyst.

    Goes in
    Hydrogen

  3. Add the acetyl group

    The 4-aminophenol solution enters a second reactor with acetic anhydride and is heated. This acetylation completes the molecule and yields the crude drug.

    Goes in
    Acetic anhydride

  4. Decolorize with charcoal

    Crude product is taken up in water with some sulfuric acid and treated with decolorizing charcoal, which removes the off color.

    Goes in
    Water

  5. Crystallize and spin

    Purification runs through repeated crystallization, with centrifuges pulling the crystals from their liquid each time.

  6. Dry, grind and pack

    Crystals are dried, then ground under dry air and packed for storage. Formulators later press the powder into tablets or dissolve it into syrups.

End of the lineAcetaminophen

Worth repeating

  • Harmon Northrop Morse first made paracetamol in 1877, but it was not tried on humans until 1887.
  • Paracetamol was shelved in favor of phenacetin for decades because of an early claim, which two research teams challenged in 1947.

Back to the ground

Follow every input upstream and acetaminophen starts as these 5 raw sources.

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Sources

Cite this page: "How acetaminophen is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/acetaminophen

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