nameIUPAC Name Generator
This IUPAC name generator does not invent a chemical-sounding string of syllables — it takes the chain length, bond type, substituents and functional group you set and applies the actual IUPAC rules to produce a name for that exact structure, the same way a chemist would work it out by hand. Get the wrong homework answer from a random name generator and you've learned nothing and lost the marks. Get one from a tool that shows its work, and you can check every step against the rules below.
👇 Click any name to copy it
Set the main chain length, pick a bond type, add up to two substituents and one functional group, then generate. The engine validates the structure (every carbon gets exactly four bonds, nothing more), works out the real longest chain — which is sometimes longer than the one you described, if a substituent you placed turns out to be part of it — numbers it for the lowest possible locants, and returns the name plus the molecular formula. If a combination isn't a valid structure, or would need a naming feature outside this tool's scope, it tells you plainly instead of returning a made-up answer.
What This Tool Can and Can't Name
Read this before you rely on a result. The generator is deliberately narrow, because a narrow tool that's always right beats a broad one that's sometimes wrong.
| Covered | Not covered — use a full structure tool instead |
|---|---|
| Straight and branched acyclic chains, 1–10 carbons | Rings, cyclic and polycyclic systems |
| One C=C or one C≡C multiple bond | Aromatic rings (benzene and derivatives) |
| One suffix functional group: alcohol, ketone, aldehyde, carboxylic acid, amine | Two or more functional groups on the same molecule |
| Halogen substituents: fluoro, chloro, bromo, iodo | R/S and E/Z stereochemistry (stereodescriptors) |
| Straight-chain substituents: methyl, ethyl, propyl, butyl | Branched substituents as prefixes (isopropyl, tert-butyl, sec-butyl) |
| Automatic longest-chain re-derivation and lowest-locant numbering | Ethers, esters, amides, nitriles, and other less common suffix groups |
For anything in the right-hand column, a full structure-drawing engine like ChemicalAid's IUPAC namer, ChemDoodle, or professional software like ACD/Labs will get you further than any parameter-based tool, this one included.
How to Use This IUPAC Name Generator
- Set the main chain length. Count the carbons in the chain you're working from — you don't need to have already found the "true" longest chain; the engine checks that for you.
- Choose the bond type. All single bonds for an alkane, or add one C=C (alkene) or one C≡C (alkyne) and set which carbon it starts on.
- Add a functional group, if there is one. Alcohol, ketone, aldehyde, carboxylic acid, or amine — pick "None" for a plain hydrocarbon or halide.
- Place up to two substituents. Pick a type (methyl, ethyl, propyl, butyl, or a halogen) and the carbon it sits on, for each.
- Generate, then read the note under the name. It tells you the molecular formula, and flags it clearly if the true parent chain turned out longer than what you set.
The Core IUPAC Rules for Naming Organic Compounds
This is the part worth actually learning — the generator applies these same four steps, every time, and showing them here means you can check its work or do it by hand next time there's no tool in front of you.
Step 1 — Find the Parent Chain
Find the longest continuous chain of carbon atoms. If the molecule has a principal functional group (an alcohol, a ketone, an acid), the parent chain must contain it — you don't get to pick a longer chain that skips past it. If two or more chains tie for longest, the tiebreaker is the one carrying the most substituents, and after that, the one that gives the lowest locants overall.
Chain length sets the stem of the name: meth- for one carbon, eth- for two, prop- for three, but- for four, then pent-, hex-, hept-, oct-, non-, dec- for five through ten. Everything else in the name attaches to that stem.
Step 2 — Number the Chain for Lowest Locants
Number the parent chain from whichever end gives the lowest set of locants, checked in this order until something breaks the tie: the suffix functional group first, then any double or triple bond, then the full set of substituent positions, then — if it's still a tie — whichever substituent is first alphabetically. An aldehyde or carboxylic acid always sits at C1 by definition, since the group can only exist at the end of a chain, so those never need this comparison at all.
The chain-length trap. Here's the mistake that catches almost everyone at least once: name butane with an ethyl group on carbon 2, and "2-ethylbutane" looks reasonable. It's wrong. Trace the actual longest chain and it runs through that ethyl branch — five carbons, not four, with a single methyl group left over. The correct name is 3-methylpentane. This generator re-derives the true longest chain from scratch for every combination you enter, specifically so this trap can't slip through — if you build "2-ethylbutane" in the tool above, it will hand back 3-methylpentane and tell you why.
Alkyl Substituent Prefixes
A substituent's name comes from its own chain length, with the ending swapped from -ane to -yl. This tool only places the straight-chain versions below, since a branched substituent (isopropyl, tert-butyl, sec-butyl) needs its own internal numbering to name correctly — worth knowing, but outside what a parameter-based tool can safely guarantee.
| Substituent | Formula | Derived from |
|---|---|---|
| Methyl | -CH3 | Methane |
| Ethyl | -C2H5 | Ethane |
| Propyl (n-) | -C3H7 | Propane |
| Butyl (n-) | -C4H9 | Butane |
| Isopropyl (not covered here) | -CH(CH3)2 | Propane, branched at C2 |
| tert-Butyl (not covered here) | -C(CH3)3 | Butane, branched at C2 |
Step 3 — Name and Order the Substituents
Each substituent gets a locant (its position number) and a name — methyl, ethyl, chloro, and so on. Two or more of the same substituent get combined with a multiplying prefix — di-, tri-, tetra- — and their locants are listed together, separated by commas: 2,3-dimethyl-, not 2-methyl-3-methyl-. Multiple different substituents are then listed in alphabetical order by their own name, ignoring the multiplying prefix — ethyl before methyl, regardless of which locant is lower.
Step 4 — Functional Group Priority
A molecule can have several types of functional group at once, but only one becomes the name's suffix — the ending that defines the compound's core identity. IUPAC ranks groups by priority; the highest-ranked one present gets the suffix, and every other group present gets demoted to a prefix instead (an oxo- prefix for a ketone, a hydroxy- prefix for an alcohol, and so on). This tool only ever places a single functional group, so you never have to run this comparison yourself here — but it's essential once you're naming real structures by hand.
| Priority | Functional group | Suffix | Example |
|---|---|---|---|
| 1 (highest) | Carboxylic acid | -oic acid | butanoic acid |
| 2 | Ester | -oate | methyl propanoate |
| 3 | Amide | -amide | ethanamide |
| 4 | Nitrile | -nitrile | propanenitrile |
| 5 | Aldehyde | -al | butanal |
| 6 | Ketone | -one | butan-2-one |
| 7 | Alcohol | -ol | propan-2-ol |
| 8 | Amine | -amine | propan-1-amine |
| 9 (lowest of these) | Halide | (prefix only — halo-) | 2-chloropropane |
Halogens never take a suffix — they're always cited as a prefix (fluoro-, chloro-, bromo-, iodo-), no matter what else is on the molecule. That's why "chloropropane" reads as a prefix on a plain alkane name rather than getting its own ending.
Common Naming Mistakes
- Picking a chain that isn't actually longest. The trap above — always trace every branch before settling on the parent chain.
- Numbering from the wrong end. Try both directions and count locants; don't assume the direction you happened to draw first is correct.
- Forgetting the alphabetical order for substituents. "4-ethyl-3-methyl-" is correct; "3-methyl-4-ethyl-" is not, even though the locants read lower-to-higher that way.
- Alphabetizing by the multiplying prefix. "Dimethyl" is alphabetized under M, not D — the "di" doesn't count.
- Dropping a locant that's actually needed. "Butanol" is ambiguous — it could be butan-1-ol or butan-2-ol. Only drop a locant when the chain is short enough that no ambiguity is possible (methanol, ethanol).
- Missing that an aldehyde or acid is always C1. These groups can only sit at the end of a chain, so they set the numbering direction before anything else is considered.
Worked Examples, Step by Step
These four were checked by hand against the generator's output while building this page, alongside a dozen more simple cases (2-chloropropane, propan-2-ol, but-2-ene, 2,3-dimethylbutane, ethanol, chloroethane, and others) to confirm the rules above are actually being applied, not just described.
| Input | Reasoning | Result |
|---|---|---|
| 4-carbon chain, methyl on C2 (entered from either end) | Only one valid parent chain; numbering flips to whichever end gives the lower locant to the methyl group | 2-methylbutane |
| 5-carbon chain, methyl on C2, ethyl on C3 | Parent chain is genuinely 5 carbons here — no longer chain exists through either branch; substituents cited alphabetically | 3-ethyl-2-methylpentane |
| 4-carbon chain, ethyl on C2 (the trap) | The true longest chain runs through the ethyl branch — 5 carbons, with the old chain's remaining carbon now a methyl substituent | 3-methylpentane |
| 3-carbon chain, alcohol on C2 | Middle carbon is the only interior position on a 3-chain; locant is needed since C1 and C3 alcohol would differ | propan-2-ol |
Example IUPAC Names by Compound Type
Every name below was generated and cross-checked, not guessed:
Alkanes
- 2-methylbutane
- 2,3-dimethylbutane
- 3-ethyl-2-methylpentane
- 2,2-dimethylpropane
- 3-methylhexane
Alkenes & alkynes
- but-2-ene
- pent-2-yne
- 3-chloropent-1-ene
- but-1-ene
Halides
- 2-chloropropane
- chloroethane
- 1,2-dichloroethane
- 1-bromo-2-methylpropane
- 2-chloro-2-methylbutane
Alcohols, ketones, aldehydes, acids, amines
- propan-2-ol
- ethanol
- butan-2-one
- pentan-2-one
- butanal
- butanoic acid
- propan-1-amine
Where IUPAC Names Actually Get Used
This isn't only a homework exercise. Safety data sheets identify chemicals by IUPAC name so a lab worker anywhere in the world knows exactly what's in a container, regardless of the trade name printed on the label. Pharmaceutical patents use systematic names to define a compound precisely enough to hold up legally. Chemistry databases like PubChem index compounds by their IUPAC name first, because it's the one identifier that doesn't depend on which country, decade, or company coined the common name. Once you can read a systematic name and reconstruct the structure from it, ingredient lists and hazard labels stop being a wall of unfamiliar syllables.
Tips for Getting IUPAC Names Right
- Draw it out first. Even a rough skeletal sketch catches chain-length mistakes that are easy to miss in your head.
- Circle every carbon once. Trace each possible "longest chain" fully before comparing lengths — half-tracing is how the ethyl-butane trap gets missed.
- Number both directions before deciding. Write out the locants each way and compare, rather than trusting instinct.
- Check the functional-group priority table if there's more than one group. The highest-priority group always becomes the suffix, not the one you happened to draw first.
- Alphabetize substituents by their own name, not their locant. Sort the words, then attach the numbers.
- When in doubt, keep the locant. Dropping a needed locant produces an ambiguous name — the safer default is to include it.
FAQ for the IUPAC Name Generator
What is IUPAC nomenclature?
It's the naming system organic chemists agreed on so that one written name maps to exactly one structure, worldwide, in any language. Instead of trade names or lab slang, a compound gets a name built from its longest carbon chain, its bonds, and the groups attached to it — the rules on this page. "IUPAC" stands for the International Union of Pure and Applied Chemistry, the body that maintains them.
Is this IUPAC name generator actually accurate?
Within its stated scope, yes — it applies the real longest-chain, lowest-locant, and functional-group-priority rules rather than gluing syllables together. It's deliberately narrow: substituted alkanes, alkenes and alkynes with at most one suffix group. Feed it something outside that (a ring, two functional groups, a structure needing a branched substituent name) and it tells you so instead of guessing. See the scope table above the generator.
How do I find the parent chain of a molecule?
Find the longest continuous carbon chain that contains your principal functional group, if you have one. Length wins first; if two chains tie for longest, the one with more substituents attached wins the tie. This trips people up constantly — see "The chain-length trap" further down, where a 4-carbon chain with an ethyl branch turns out to actually be a 5-carbon chain in disguise.
What is a locant in chemistry?
A locant is the number that says where something sits on the chain — the "2" in 2-chloropropane, the "3" in but-3-en-1-ol. You always number the chain in whichever direction hands out the lowest set of locants, checked in order: the suffix group first, then double or triple bonds, then substituents as a group, then whichever substituent comes first alphabetically.
How do you decide which functional group gets the suffix?
When a molecule has more than one type of functional group, IUPAC ranks them by priority — carboxylic acids outrank esters, which outrank amides, aldehydes, ketones, alcohols, amines, and so on down the list in the priority table above. The highest-ranked group becomes the suffix (the "-ol", "-one", "-oic acid" ending); everything lower just gets cited as a prefix. This tool only ever places one suffix group, so that ranking step is already decided for you.
Why is the locant sometimes left off a name, like "ethanol" instead of "ethan-1-ol"?
When a chain is so short that a group can only physically sit in one place, citing the number adds nothing, so it's dropped by convention — ethanol, not ethan-1-ol; chloroethane, not 1-chloroethane. The moment there's a second thing on the chain needing a locant, or the chain is long enough for the position to be ambiguous, the number comes back.
Can this tool name rings, benzene rings, or stereochemistry?
No, and it says so rather than pretending. Rings, aromatic systems, and R/S or E/Z stereochemistry are outside this tool's scope — see the capability table above the generator for what it does and doesn't cover, and use a full structure-drawing tool like ChemDoodle or ACD/Labs for those cases.
What's the difference between an IUPAC name and a common name?
A common name is whatever stuck by habit — acetone, formaldehyde, vinegar. An IUPAC name is built from a fixed rule set, so anyone anywhere can reconstruct the exact structure from the name alone, no memorization required. Acetone's IUPAC name is propan-2-one; formaldehyde's is methanal. Common names survive because they're shorter and familiar, not because they're more correct.
Why did the generator give me a different chain length than I set?
Because your "main chain" input isn't always the true longest chain in the molecule — a branch you placed as a substituent can turn out to be longer than the chain running past it. The generator checks this for every combination and renumbers from the real longest chain when that happens, exactly as the IUPAC rules require, and flags it in the result so you can see what changed.
