# IUPAC Name Generator - Organic Structure to Name and Name to Structure

> Name organic compounds from SMILES: IUPAC 2013 and traditional names, highlighted parent chain and step-by-step reasoning. Also name-to-structure and a quiz.

- URL: https://qilingtools.com/en/math/organic-name
- Category: Math Tools (https://qilingtools.com/en/math)
- Tags: [Math](https://qilingtools.com/en/tags/math), [Chemistry](https://qilingtools.com/en/tags/chemistry), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

Systematic (IUPAC) names are built in four steps: choose the parent chain or ring, number it, list the substituent prefixes, and assemble the name. For (CH₃)₂CHCH=CH₂ the parent is the four-carbon chain containing the double bond, numbered from the end nearer the C=C, so the name is 3-methylbut-1-ene (traditionally 3-methyl-1-butene). Enter a SMILES string and the tool detects the functional groups, picks the principal characteristic group (acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine), compares every candidate parent and numbering direction, highlights the parent chain with its locants and explains each decision. It returns the IUPAC 2013 name (longest chain first, locants next to the -ene/-ol they modify, e.g. butan-2-ol), a traditional/CAS-style name (most multiple bonds first, locants in front, e.g. 2-butanol), common names such as isopentane, ethyl acetate or p-xylene, and the Chinese names. It also works in reverse — type an English or Chinese name, including cis/trans, E/Z, o-/m-/p-, esters (ethyl acetate), ethers (ethyl methyl ether) and amines (diethylamine), to get the structure — and a quiz mode draws random structures for you to name. Coverage: acyclic and monocyclic compounds, including benzene derivatives, with alkenes, alkynes, halides, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, esters, amines, nitriles, amides and nitro groups; everything runs in your browser.

## How to use

1. In Structure → name, enter a SMILES string such as CC(C)C=C or pick an example molecule
2. Read the highlighted parent chain, the IUPAC 2013 and traditional names, and the naming steps; switch rule sets to compare them
3. Use Name → structure to draw a molecule from its name, or open Practice to test yourself

## Features

- IUPAC 2013 names plus traditional/CAS-style names and common names
- Parent chain or ring highlighted on the skeletal drawing with locants
- Step-by-step reasoning: functional groups, parent selection, numbering, prefix order
- Name → structure for English and Chinese names, with cis/trans, E/Z and o-/m-/p-
- Alkanes, alkenes, alkynes, haloalkanes, alcohols, phenols, ethers, aldehydes, ketones, acids, esters, amines, nitriles, amides, nitro compounds
- Benzene derivatives such as toluene, xylenes, phenol, aniline and benzoic acid
- Naming quiz with three levels and instant feedback
- Links to the isomer generator for the same molecular formula

## FAQ

### Which comes first: the longest chain or the chain with the double bond?

Under the 1979/1993 IUPAC rules still taught in many courses, the parent chain must contain the maximum number of multiple bonds, and only then be the longest. The 2013 IUPAC recommendations reverse this: the longest chain wins and unsaturation is considered next. So CH₂=C(CH₂CH₃)CH₂CH₂CH₃ is 2-ethylpent-1-ene by the old rule but 3-methylidenehexane by the 2013 rule. In both, the chain must first carry the most principal characteristic groups. The tool shows both and explains which criterion decided.

### How are substituent prefixes ordered?

Prefixes are cited in alphabetical order of their names, ignoring multiplying prefixes such as di- and tri- and the italic sec-/tert-: 3-ethyl-2-methylpentane, 2-bromo-4-methylpentane. If both numbering directions give the same set of locants, the prefix cited first gets the lower locant.

### Is it but-1-ene or 1-butene?

Both describe the same compound. Current IUPAC recommendations place a locant immediately before the part of the name it refers to (but-1-ene, butan-2-ol, 3-methylpent-2-ene), while traditional and CAS-style names put it in front of the parent (1-butene, 2-butanol, 3-methyl-2-pentene). The tool gives both forms and accepts either when you type a name.

### What kinds of molecules are supported?

Acyclic and single-ring molecules (including one benzene ring) containing C, H, O, N and halogens, with C=C, C≡C, halogen, OH, ether, CHO, ketone, COOH, one ester group, amine, nitrile, amide and nitro groups. Fused or bridged rings, heterocycles, acyl halides, anhydrides and sulfur or phosphorus compounds are outside the scope and are reported as such.

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