Home / Learn / Chemistry / EsterificationTool #L179 (formerly #1298)

Esterification

Pick a carboxylic acid and an alcohol and join them: see the OH and H leave as water, and get the ester's name, formula, molar mass and smell. Split it again with sodium hydroxide, and at Class 11–12 level work out how much ester forms at equilibrium.

Keep it one tap away for everyday use.

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  1. Acid
  2. Join
  3. Name
  4. Practise
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    Try this

    • Ethanoic acid and pentan-1-ol give a banana smell. Which pair smells of pineapple?
    • The name comes from the alcohol first, then the acid: ethanol + methanoic acid gives ethyl methanoate.
    • At Class 11–12 level, use 3 mol of alcohol for 1 mol of acid. Why does the yield go up?
    • Press "Split with NaOH" to run the reaction backwards. With the long acids in fats, this is how soap is made.

    Check yourself

    Use C = 12, H = 1, O = 16. Nothing is saved.

      What it does

      A carboxylic acid and an alcohol, warmed with a few drops of concentrated sulfuric acid, join to make an ester and water. Esters often smell sweet and fruity, which is why they are used in flavours and perfumes. This page shows the reaction:

      • pick one of five acids (methanoic, ethanoic, propanoic, butanoic, benzoic) and one of six alcohols,
      • the picture marks the OH of the acid and the H of the alcohol that leave as water; Join them draws the ester with its new C–O bond,
      • you get the ester’s name, condensed and molecular formula, molar mass and smell,
      • Split with NaOH runs it backwards (saponification), the reaction that turns fats into soap,
      • at the Class 11–12 level, a calculator finds how much ester there is at equilibrium from the amounts of acid, alcohol and water and the constant K.

      It follows the Class 10 chapter on carbon and its compounds (esterification and saponification), Class 12 carboxylic acids, and Class 11 chemical equilibrium.

      Name the acid and alcohol themselves with the IUPAC namer; esters with the same formula as acids are functional isomers in the isomer explorer, and pushing an equilibrium one way is explored in le Chatelier sandbox.

      How to use it

      1. Choose the Acid and the Alcohol. The boxed atoms are the ones that leave as water.
      2. Press Join them. Read the equation, how the name is built, the formula and the smell.
      3. Press Split with NaOH to see the salt and alcohol you get back. Start again returns to the beginning.
      4. Switch to Class 11–12 and type the moles of acid, alcohol and any water at the start, and K.

      A worked example

      Ethanoic acid + ethanol: CH₃COOH + CH₃CH₂OH ⇌ CH₃COOCH₂CH₃ + H₂O. The alcohol gives the first part of the name (ethyl) and the acid the second (ethanoic acid → ethanoate): ethyl ethanoate, C₄H₈O₂, 60 + 46 − 18 = 88 g/mol. It smells sweet, like nail-polish remover.

      At equilibrium with 1 mol of each and K = 4: x² ÷ (1 − x)² = 4, so x ÷ (1 − x) = 2 and x = 2/3 mol, a 66.7 % yield. With 3 mol of ethanol instead, x = 0.903 mol, a 90.3 % yield: an excess of one reactant pushes the equilibrium towards the ester.

      Ethanoic acid + pentan-1-ol gives pentyl ethanoate, which smells of banana.

      Tips

      • In an ester name, the part ending in -yl comes from the alcohol and the part ending in -oate from the acid.
      • An ester and a carboxylic acid can share a formula: ethyl ethanoate and butanoic acid are both C₄H₈O₂.
      • The sulfuric acid is a catalyst; it is not part of the equation.

      Check yourself

      Four fresh questions each time: name an ester, its molar mass, and two equilibrium amounts. Nothing is saved.

      FAQ

      Can I make esters at home? No: concentrated sulfuric acid is dangerous. In school this is done by a teacher, often in a fume cupboard.

      Is this from the NCERT book? It covers the same topic with fibub’s own drawings and examples. fibub is not part of NCERT.

      Where the numbers come from

      • Esterification, the naming of esters (alkyl alkanoate), saponification and the ¹⁸O labelling result are standard school chemistry. The equilibrium constant K ≈ 4 for ethanoic acid and ethanol is a round classroom value. The smells are common kitchen-chemistry descriptions; smell is subjective. Written for fibub.
      • Formulas checked by hand (ethyl ethanoate C₄H₈O₂ = 88, pentyl ethanoate C₇H₁₄O₂ = 130, methyl benzoate C₈H₈O₂ = 136) and for all 30 pairs acid + alcohol = ester + water by mass; the equilibrium checked against sympy.solve (1 : 1 gives 2/3 mol; 1 : 3 gives 0.9028 mol).

      Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.

      Last updated 2026-11-09.

      Change log for Esterification

      1. Add #1298 Esterification and ester names Details on GitHub

      Every change to fibub

      Related tools

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