Understanding Organic Chemistry Nomenclature

Expert reviewed • 04 March 2025 • 6 minute read

Introduction

Organic chemistry forms a crucial part of HSC Chemistry studies, focusing on compounds containing carbon. This article explores the systematic naming (nomenclature) and structural features of key organic compounds, essential for understanding their properties and reactions.

Key Organic Families

Alkanes - The Foundation

Alkanes are the simplest organic compounds, characterized by single bonds between carbon atoms. Their general formula is $C_nH_{2n+2}$ .

Naming Rules:

End with suffix "-ane"
Prefix indicates carbon count
Examples: methane ( $CH_4$ ), ethane ( $C_2H_6$ ), propane ( $C_3H_8$ )

Alkenes - Double Bond Features

Alkenes contain at least one carbon-carbon double bond ( $C=C$ ). Their general formula is $C_nH_{2n}$ .

Naming Rules:

End with suffix "-ene"
Number indicates double bond position
Examples: ethene ( $C_2H_4$ ), prop-1-ene ( $C_3H_6$ )

Alkynes - Triple Bond Structures

Alkynes feature carbon-carbon triple bonds ( $C≡C$ ). Their general formula is $C_nH_{2n-2}$ .

Naming Rules:

End with suffix "-yne"
Number indicates triple bond position
Examples: ethyne ( $C_2H_2$ ), prop-1-yne ( $C_3H_4$ )

Alcohols - OH Groups

Alcohols contain the hydroxyl group ( $-OH$ ).

Classification:

Primary: $RCH_2OH$
Secondary: $R_2CHOH$
Tertiary: $R_3COH$

Naming Rules:

End with suffix "-ol"
Number indicates OH position
Examples: ethanol ( $C_2H_5OH$ ), propan-2-ol ( $C_3H_7OH$ )

Aldehydes and Ketones - Carbonyl Groups

Both contain the carbonyl group ( $C=O$ ), but in different positions:

Aldehydes: Terminal $C=O$ group
Ketones: Internal $C=O$ group

Naming Rules:

Aldehydes: End with "-al"
Ketones: End with "-one"
Examples: ethanal ( $CH_3CHO$ ), propanone ( $CH_3COCH_3$ )

Carboxylic Acids - COOH Groups

Contain the carboxyl group ( $-COOH$ ).

Naming Rules:

End with suffix "-oic acid"
Example: ethanoic acid ( $CH_3COOH$ )

Esters - Derived from Acids

Form from reaction between alcohols and carboxylic acids.

Naming Rules:

Format: [alkyl group] [acid name with -oic replaced by -oate]
Example: methyl ethanoate ( $CH_3COOCH_3$ )

Amines and Amides - Nitrogen Compounds

Amines:

Contain $-NH_2$ group
End with suffix "-amine"
Example: ethanamine ( $CH_3CH_2NH_2$ )

Amides:

Contain $-CONH_2$ group
End with suffix "-amide"
Example: ethanamide ( $CH_3CONH_2$ )

Practice Tips

Focus on identifying functional groups first
Learn systematic naming rules progressively
Practice drawing structures from names and vice versa
Pay attention to position numbers in complex molecules

Fundamentals of Hydrocarbons: Structure, Properties, and Reactions

Understanding Molecular Isomers: Same Formula, Different Structures

Return to Module 7: Organic Chemistry