IUPAC Nomenclature Calculator
Build a systematic IUPAC name for a simple open-chain organic compound using the standard IUPAC nomenclature rules. Enter the parent chain length, the compound class, the principal group locant, and one alkyl or halogen substituent. The calculator returns the assembled name plus a breakdown of which rule was applied.
IUPAC nomenclature is the worldwide standard for naming organic compounds. The calculator on this page follows the 2013 IUPAC recommendations for simple open-chain (acyclic) compounds with a single principal functional group.
The Five Steps of IUPAC Nomenclature
- Find the parent chain. Pick the longest continuous chain of carbons that contains the principal functional group. The carbon count sets the root name (meth-, eth-, prop-, ..., icos-).
- Number the chain. Start numbering from the end that gives the principal group the lowest locant. If there is a tie, the next tiebreaker is the lowest set of substituent locants.
- Name the principal group as a suffix. Alkane (-ane), alkene (-ene), alkyne (-yne), alcohol (-ol), aldehyde (-al), ketone (-one), carboxylic acid (-oic acid), and amine (-amine) are the common suffixes.
- Name substituents as prefixes. Alkyl branches (methyl, ethyl, propyl), halogens (fluoro, chloro, bromo, iodo), alkoxy groups for ethers, and others go in front of the root, listed alphabetically (ignoring di, tri, tetra for ordering).
- Assemble the name. {prefix-locant}-{substituent}-{parent root}-{locant}-{suffix}. Hyphens separate numbers and letters, but not two adjacent letter segments.
Priority of Principal Groups (Highest First)
Carboxylic acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine > alkene > alkyne > alkane. The highest-priority group present becomes the suffix. All lower-priority groups become prefixes.
Worked Example: 3-Chloro-2-methylbutan-1-ol
- Parent chain: four carbons, so the stem is but-.
- Principal group: alcohol (-OH). Suffix is -ol.
- Number from the end nearest the -OH: C1 = CH2OH, C2, C3, C4.
- Substituents: methyl at C2 (2-methyl), chloro at C3 (3-chloro).
- Alphabetize prefixes: chloro before methyl.
- Name: 3-chloro-2-methylbutan-1-ol.
Hyphens and Punctuation
Hyphens appear between numbers and letters (2-methyl, but-1-ene) and between adjacent locant-substituent blocks (3-chloro-2-methyl). They do not appear between the trailing letter of the last substituent and the opening letter of the parent root, so 2-methyl joins to butane as 2-methylbutane.
Retained Common Names
A short list of traditional names is retained in the IUPAC 2013 recommendations: acetic acid, formic acid, acetone, formaldehyde, benzene, toluene, phenol. The preferred systematic forms are ethanoic acid, methanoic acid, propan-2-one, methanal, and so on.
What This IUPAC Nomenclature Calculator Does Not Cover
The calculator handles open-chain parents from 1 to 20 carbons, a single principal functional group, one alkyl branch, and one halogen. It does not cover rings (cyclohexane, benzene derivatives), stereochemistry descriptors (R/S, E/Z, cis/trans), multiple different principal groups, amides and esters (which need suffix splitting), or multi-branched quaternary carbons. For those, use PubChem's Structure-to-Name service or commercial drawing software.