# IUPAC Nomenclature Calculator Apply IUPAC nomenclature rules: parent chain, numbering, principal group suffix, substituent prefixes. Builds systematic names for simple organic compounds. ## What this calculates 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. ## Inputs - **Longest Carbon Chain (carbons)** — min 1, max 20 — The longest continuous carbon chain that contains the principal functional group. Accepts 1 to 20 carbons. - **Compound Class** — options: Alkane (saturated hydrocarbon), Alkene (contains C=C), Alkyne (contains C≡C), Alcohol (-OH suffix), Aldehyde (-CHO suffix), Ketone (=O on internal carbon), Carboxylic acid (-COOH suffix), Ether (as alkoxy prefix), Alkyl halide (halo prefix only) — Pick the class that contains the highest-priority group. This sets the name suffix per IUPAC rules. - **Locant for Principal Group** — min 1, max 20 — Position of the double bond, triple bond, -OH, C=O, or other principal group after low-locant numbering. Ignored for alkanes, aldehydes, and carboxylic acids. - **Branch Type** — options: No branch, Methyl (-CH₃), Ethyl (-C₂H₅), Propyl (-C₃H₇), Isopropyl (propan-2-yl) — Most common alkyl substituent on the parent chain. Select none for unbranched parents. - **Branch Locant** — min 1, max 20 — Position of the alkyl branch on the parent chain. Use lowest locants per IUPAC rule. - **Halogen Substituent** — options: None, Fluoro (-F), Chloro (-Cl), Bromo (-Br), Iodo (-I) — Optional halogen substituent. For alkyl halide class, this is the principal group. - **Halogen Locant** — min 1, max 20 — Position of the halogen on the parent chain. ## Outputs - **IUPAC Systematic Name** — formatted as text — The complete IUPAC name assembled by the calculator from your inputs. - **Parent Root** — formatted as text — The parent-chain root (meth-, eth-, prop-, but-, ...) for the given carbon count. - **Locant Breakdown** — formatted as text — List of numbered positions and the groups attached at each one. - **Rule Applied** — formatted as text — The key IUPAC rule used to pick this particular name. ## Details 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** 1. **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-). 2. **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. 3. **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. 4. **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). 5. **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. ## Frequently Asked Questions **Q: What is an IUPAC nomenclature calculator?** A: An IUPAC nomenclature calculator applies the rules set out by the International Union of Pure and Applied Chemistry to build a systematic name for an organic compound. This calculator takes the parent chain length, compound class, principal group locant, and one substituent, then assembles the name step by step and tells you which IUPAC nomenclature rule was used. **Q: How does the calculator pick the parent chain?** A: You tell it the number of carbons in the longest chain containing the principal functional group. In textbook practice, you pick that chain first by inspection. The calculator then uses the carbon count to select the root (meth- for C1, eth- for C2, prop- for C3, but- for C4, and so on up to icos- for C20). **Q: What is the rule for numbering the carbon chain?** A: Start numbering at the end of the chain that gives the principal functional group the lowest possible locant. If the principal group is equidistant from both ends, number to give the set of substituents the lowest locants at the first point of difference. Alphabetical order is the last tiebreaker. **Q: How are substituents listed in an IUPAC name?** A: Alphabetically, not by locant. Multiplying prefixes (di, tri, tetra) are ignored for ordering. So a compound with methyl and ethyl branches is listed as 'ethyl...methyl', with locants attached to each. Dimethyl is alphabetized as 'methyl', not 'dimethyl'. **Q: Which functional group becomes the suffix when there are several?** A: The highest-priority group does. The standard IUPAC priority order, from highest to lowest, is carboxylic acid, ester, amide, nitrile, aldehyde, ketone, alcohol, amine, alkene, alkyne, alkane. Lower-priority groups are named as prefixes. This calculator asks you to pick the class containing the highest-priority group so it can apply the correct suffix. **Q: Does this follow IUPAC 2013 rules or the older 1979 rules?** A: The calculator follows the 2013 IUPAC recommendations on preferred names, which is the current convention taught in general and organic chemistry courses. The main practical differences from the 1979 rules are locant placement (pent-2-ene rather than 2-pentene) and a slightly revised list of retained common names. --- Source: https://vastcalc.com/calculators/chemistry/iupac-nomenclature Category: Chemistry Last updated: 2026-04-08