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Naming organic compounds

Build a chain, hang groups off it, and watch the name assemble.

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Scientific learning path

  1. 01UnderstandLive
  2. 02ExploreLive
  3. 03ExperimentLive
  4. 04ObserveLive
  5. 05ExplainLive
  6. 06ApplyLive
  7. 07TestBuilding
Explanation mode
methyl4321

A skeletal structure: every corner is a carbon and the hydrogens are left out. The numbers run in whichever direction the name uses, so the drawing and the name can be checked against each other.

on carbon
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Description of this simulation

2-methylbutane, formula C5H12. The parent chain has 4 carbons. Numbering runs right to left, because that gives the lower locants: 2.

2-methylbutane

C5H12

Parent chain
4
Numbered
right to left
Locants
2
  • methyldrawn at carbon 3

The three rules, in order

Find the longest chain
The parent is the longest chain of carbons, whichever way it runs across the page. A branch can easily be part of a longer chain than the one drawn horizontally.
Number for the lowest locants
Number from whichever end gives the lower set of locants, comparing them one at a time rather than adding them up. This is why it is 2-methylbutane and never 3-methylbutane.
Alphabetise by the group name
Order the prefixes alphabetically by the substituent itself. Di, tri and tetra are counting words and are ignored, so ethyl comes before dimethyl.

What this model shows — and what it simplifies

Educational Model

Saturated open-chain hydrocarbons with simple alkyl and halogen substituents.

Where do we see this in real life?

A name is an instruction for building the molecule. Two chemists on opposite sides of the world make the same compound from the same word, which is the entire reason the rules are worth learning.