AP | A-Level | IB | NCERT 11 + 12 – FREE NOTES, RESOURCES AND VIDEOS!
S1.1 - Introduction to the particulate nature of matter S1.2 - The nuclear atom S1.3 - Electron configurations S1.4 - Counting particles by mass - The mole S1.5 - Ideal gases S2.1 - The ionic model S2.2 - The covalent model S2.3 - The metallic model S2.4 - From models to materials S3.1 - The periodic table - Classification of elements S3.2 - Functional groups - Classification of organic compounds R1.1 - Measuring enthalpy changes R1.2 - Energy cycles in reactions R1.3 - Energy from fuels R1.4 - Entropy and spontaneity AHL R2.1 - How much? The amount of chemical change R2.2 - How fast? The rate of chemical change R2.3 - How far? The extent of chemical change R3.1 - Proton transfer reactions R3.2 - Electron transfer reactions R3.3 - Electron sharing reactions R3.4 - Electron-pair sharing reactions

S3.2 - Functional groups - Classification of organic compounds

3.2.1 Representing Organic Compounds 3.2.2 Functional Group 3.2.3 Homologous Series 3.2.4 Trends and Properties of Homologous Series 3.2.5 Nomenclature 3.2.6 Structural Isomerism 3.2.7 Stereoisomerism and Chirality (AHL) 3.2.8 Mass Spectrometry (MS) of Organic Compounds (AHL) 3.2.9 Infrared (IR) Spectroscopy and Greenhouse Gases (AHL) 3.2.10 Proton NMR Spectroscopy (AHL) 3.2.11 Splitting Patterns in Proton NMR Spectroscopy (AHL) 3.2.12 Interpreting Spectra (AHL)

IUPAC Naming Rules

Specification Reference S3.2.5

IUPAC Naming Rules

You should be able to use IUPAC (International Union of Pure and Applied Chemistry) naming rules to name a variety of organic compounds.

Steps for Naming Organic Compounds:

Applying IUPAC Rules to Name Organic Compounds

Class (a–g) Suffix Structure / Key Rule Examples
Alkanes -ane Only single bonds between carbon atoms. CH4
Methane
Alkenes -ene One or more C=C double bonds. Number the double bond position. CH3CH=CHCH3
But-2-ene
Alkynes -yne One or more C≡C triple bonds. CH≡CCH3
Prop-1-yne
Alcohols -ol OH (hydroxyl) group attached to a carbon atom. Number the position of the OH group. CH3CH(OH)CH3
Propan-2-ol
Aldehydes -al CHO group at the end of a molecule. No need to number the group, it's always at position 1. CH3CH2CH2CHO
Butanal
Ketones -one C=O (carbonyl) group within the carbon chain. Number to show position of C=O. CH3CH2COCH3
Butan-2-one
Carboxylic Acids -oic acid COOH group at the end of the molecule. Always at position 1; no number needed. CH3CH2CH2COOH
Butanoic acid

Naming Branched and Substituted Compounds

Example 2-Methylpentane (C6H14)
Longest chain = pentane, with a methyl group at carbon 2.

IB Chemistry example showing 2-methylpentane with the longest chain and a methyl substituent at carbon 2

Naming Cyclic Compounds

Cyclic compounds are named with the prefix “cyclo-”.

Example Cyclohexane (C6H12)
Six-membered ring.

IB Chemistry displayed ring structure of cyclohexane C6H12

Applying IUPAC Rules to Draw Structures from Names

Example Propan-1-ol

Longest carbon chain = 3 (prop)

IB Chemistry step showing the three-carbon chain for propan-1-ol

Type of functional group: -OH (anol) and Bonding position on carbon 1 (-1-ol)

IB Chemistry step adding the hydroxyl group at carbon 1 for propan-1-ol

Giving the final structure of

IB Chemistry final displayed formula of propan-1-ol

Summary Table: IUPAC Naming Rules

Rule Details Quick Reference
Longest Chain Choose the longest continuous carbon chain. Meth-, Eth-, Prop-, But-, Pent-, Hex-
Functional Group Determines the suffix (end of name) and carbon number priority. -ol, -al, -one, -oic acid, -ene, -yne
Numbering Assign lowest possible carbon numbering to the functional group and double/triple bonds. Use 1-, 2-, etc.; commas between numbers
Substituents Name and number alkyl groups as prefixes; alphabetise if multiple. 2-Methyl-, 3-Ethyl-, di-/tri- for repeats
Punctuation Commas between numbers; hyphens between numbers and letters. e.g., But-2-ene; Propan-2-ol