Home / Learn / Chemistry / IUPAC namerTool #L49 (formerly #1104)

IUPAC namer

Build a carbon chain of up to 10 carbons, tap carbons to add methyl and ethyl branches, add a double or triple bond and one functional group (–OH, –CHO, C=O, –COOH, –Cl, –Br). Get the IUPAC name with each step explained, the molecular formula and the homologous series, and test yourself on new structures.

Keep it one tap away for everyday use.

Bookmark IUPAC namer?

Press Ctrl + D now. Your browser opens its own bookmark box, where you choose the name and folder.

  1. Build
  2. Branches
  3. Name
  4. Check
Nothing is uploadedWorks offline once open

Build a molecule

Carbons in the chain
5

Tap a carbon in the drawing to add a branch: methyl → ethyl → two methyls → none.

Blue numbers and thick bonds: the chain used for the name, numbered the IUPAC way.

How the name is built

    Homologous series

    CarbonsNameFormula

    Try this

    • Make a 4-carbon chain and tap carbon 2 for a methyl: 2-methylbutane. Now move the methyl to carbon 1. Is it still a branch, or just a longer chain?
    • Make pentane and put an ethyl on carbon 2. The longest chain now runs through the branch: the name changes to 3-methylhexane.
    • Put –OH on carbon 4 of a 5-carbon chain. Why is it pentan-2-ol and not pentan-4-ol?
    • Add a double bond and an –OH: which one decides the numbering?
    • Change the chain length with the series group fixed: each member differs by CH₂.

    Check yourself

    Pick the right IUPAC name for each structure. New questions every time; nothing is saved.

    What it does

    Organic compounds have names that tell you their structure, if you know the rules. This page lets you build a molecule and watch its IUPAC name change as you go. Use − and + to set how many carbons are in the chain, choose a double or triple bond and a functional group, and (in Class 11 mode) tap a carbon in the drawing to hang a methyl or ethyl branch on it. The name appears at once with the steps that build it, the molecular formula, and the family (homologous series) it belongs to.

    The blue numbers and thick bonds show the chain the name is based on. Often it is not the chain you drew: put an ethyl near the end of a chain and the longest chain runs through the branch.

    It follows Class 10 Science (carbon and its compounds: saturated and unsaturated compounds, homologous series, nomenclature with functional groups) and Class 11 Chemistry (organic chemistry basics: IUPAC nomenclature). Use Class 10 for straight chains only. To see the electron dots of the bonds, open the lewis structures tool; to check a formula’s rings and double bonds use the unsaturation; for the molar mass of the formula, the molar mass calculator.

    How to use it

    1. Set Carbons in the chain (1 to 10).
    2. Choose a Multiple bond and where it goes, if you want one.
    3. Choose a Functional group and the carbon it sits on. –CHO and –COOH can only be at an end; a ketone C=O must be inside the chain.
    4. In Class 11 mode, tap a carbon to cycle its branches: methyl, ethyl, two methyls, none.
    5. Read the name, the formula, the series and How the name is built. The Homologous series table lists the first members of the same family.
    6. Try Check yourself: pick the right name for three new structures.

    Worked example

    Start with 5 carbons (pentane, C₅H₁₂). Tap carbon 2 twice to give it an ethyl branch. The longest chain is now 6 carbons, through the branch, so the root is “hex-”. Number from the end nearer the branch: the methyl left over sits on carbon 3. The name is 3-methylhexane, formula C₇H₁₆, an alkane (CₙH₂ₙ₊₂).

    Now reset, keep 5 carbons, choose Alcohol –OH on carbon 4 and tap carbon 2 once for a methyl. The –OH must get the lowest number, so the chain is numbered from the other end: –OH on carbon 2, methyl on carbon 4. The name is 4-methylpentan-2-ol (C₆H₁₄O).

    Rules the tool follows

    • Choose the chain: it must hold the principal group and the double or triple bond; then the longest; then the one with most branches.
    • Number it so the principal group gets the lowest number, then the multiple bond, then the branches.
    • Suffixes: –oic acid > –al > –one > –ol. Chloro and bromo are always prefixes.
    • Prefixes go in alphabetical order (ethyl before methyl); di-, tri- don’t count.

    FAQ

    Why “propene” and not “prop-1-ene”? When there is only one place a group or bond can be, school books leave the number out (ethanol, propanone, propanal). With branches, the number is always given.

    Is this an NCERT tool? No. It is a free fibub page made for these chapters; it runs on your device.

    Where the numbers come from

    • IUPAC nomenclature rules for open-chain compounds as taught in school: the principal chain holds the principal group and the multiple bond and is then the longest (the 1993 recommendations' order; the 2013 recommendations choose the longest chain first), lowest locants, alphabetical prefixes, seniority acid > aldehyde > ketone > alcohol, locants placed before the suffix (but-2-ene, propan-2-ol). Written fresh for fibub.
    • Checked against 34 standard IUPAC names of simple compounds, including ones where the longest chain runs through a drawn branch (3-methylhexane, 2-ethylpent-1-ene) and ones with a group and a double bond (but-3-en-2-ol, but-2-enal); molecular formulas checked by counting atoms.

    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 IUPAC namer

    1. Add #1104 Carbon chain builder and IUPAC namer Details on GitHub

    Every change to fibub

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