IUPAC Nomenclature of Organic Compounds: Complete Rules, Functional Group Priority Order & Examples with Free PDF Download
IUPAC Nomenclature of Organic Compounds — Competishun
IUPAC Nomenclature of Organic Compounds: Complete Rules, Functional Group Priority Order & Examples with Free PDF Download
Organic chemistry has millions of compounds, so we cannot rely on random common names. That is why the International Union of Pure and Applied Chemistry (IUPAC) created a systematic naming method: give every compound one unique, logical name built from its structure. Once you learn the pattern, you can name almost any compound, and read any name back into a structure.
This is a complete guide to IUPAC nomenclature of organic compounds for Class 11, JEE and NEET, covering the naming rules, word roots, prefixes and suffixes, the all-important functional group priority order, step-by-step naming and worked examples. Grab the free PDF below for quick revision.
Download the IUPAC Nomenclature Rules PDF
Get all IUPAC naming rules, word roots, suffixes, the functional group priority order and solved examples in one clean PDF, free. Perfect for Class 11, JEE and NEET revision.
Download Free PDFThe 4 Parts of an IUPAC Name
Every IUPAC name is built by joining four parts in this order.
Word Roots (Number of Carbons)
The word root tells you how many carbons are in the main chain.
| Carbons | Root | Carbons | Root |
|---|---|---|---|
| 1 | Meth | 6 | Hex |
| 2 | Eth | 7 | Hept |
| 3 | Prop | 8 | Oct |
| 4 | But | 9 | Non |
| 5 | Pent | 10 | Dec |
| Memory trick: Meth-Eth-Prop-But are the tricky four. From Pent onwards it follows Greek numbers. | |||
Primary Suffix (Saturation)
| Bond Type | Primary Suffix | Example |
|---|---|---|
| All single bonds (alkane) | -ane | CH₃-CH₃ = Ethane |
| One double bond (alkene) | -ene | CH₂=CH₂ = Ethene |
| One triple bond (alkyne) | -yne | CH≡CH = Ethyne |
| The position of the double or triple bond is shown with the lowest locant, e.g. but-2-ene. | ||
Functional Group Priority Order (Seniority)
This is the most important table in the chapter. When a compound has more than one functional group, the senior-most group becomes the suffix, and all others are written as prefixes.
| Priority | Functional Group | Suffix | Prefix (if not senior) |
|---|---|---|---|
| 1 | Carboxylic acid (-COOH) | -oic acid | carboxy |
| 2 | Sulphonic acid (-SO₃H) | -sulphonic acid | sulpho |
| 3 | Ester (-COOR) | -oate | alkoxycarbonyl |
| 4 | Acid halide (-COX) | -oyl halide | halocarbonyl |
| 5 | Amide (-CONH₂) | -amide | carbamoyl |
| 6 | Nitrile (-CN) | -nitrile | cyano |
| 7 | Aldehyde (-CHO) | -al | oxo / formyl |
| 8 | Ketone (>C=O) | -one | oxo |
| 9 | Alcohol (-OH) | -ol | hydroxy |
| 10 | Amine (-NH₂) | -amine | amino |
| Always prefixes only: ether (alkoxy), halogens (fluoro, chloro, bromo, iodo), nitro, nitroso, alkyl. Double/triple bonds stay as -ene/-yne in the parent chain. | |||
Common Substituent Prefixes
| Group | Prefix | Group | Prefix |
|---|---|---|---|
| -CH₃ | methyl | -F | fluoro |
| -C₂H₅ | ethyl | -Cl | chloro |
| -OH (not senior) | hydroxy | -Br | bromo |
| -NH₂ (not senior) | amino | -I | iodo |
| -NO₂ | nitro | -OR | alkoxy |
| Multiplying prefixes di, tri, tetra are used for repeated groups but are ignored while arranging prefixes alphabetically. | |||
How to Name a Compound: Step by Step
Find the parent chain
Select the longest continuous carbon chain that contains the principal (senior-most) functional group.
Number the chain
Number so the principal functional group gets the lowest possible locant. If tied, give substituents the lowest locants.
Name the parent
Combine word root + primary suffix (ane/ene/yne) + secondary suffix (the functional group).
Add substituents
Write all substituents as prefixes in alphabetical order, each with its locant.
Punctuate correctly
Commas between numbers, hyphens between numbers and letters. Use di, tri, tetra for repeats.
Worked Examples
| Structure | IUPAC Name | Why |
|---|---|---|
| CH₃-CH₂-OH | Ethanol | 2 C + alcohol → eth + an + ol |
| CH₃-CHO | Ethanal | 2 C + aldehyde → eth + an + al |
| CH₃-CO-CH₃ | Propan-2-one | 3 C + ketone at C2 → propan-2-one |
| CH₃-CH₂-COOH | Propanoic acid | 3 C + acid → propan + oic acid |
| CH₂=CH-CH₃ | Prop-1-ene | 3 C + double bond at C1 |
| (CH₃)₂CH-CH₃ | 2-Methylpropane | 3 C chain + methyl at C2 |
| Practise reading each name back into its structure, that two-way skill is what JEE and NEET test. | ||
Common Mistakes to Avoid
- Wrong parent chain: The longest chain must include the principal functional group, even if it is not the visually longest
- Wrong numbering: The principal functional group gets the lowest locant, not the substituent
- Alphabetical slips: Arrange prefixes alphabetically, ignoring di/tri but not iso
- Missing locants: Always show the position of the functional group and each substituent
How to Use This Guide
- Learn word roots + suffixes first: They are the building blocks of every name
- Memorise the priority order: It decides your suffix every single time
- Practise both ways: Name structures, and draw structures from names
- Revise from the PDF: Keep it handy before every organic chemistry test
Get the Complete IUPAC Rules PDF Free
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