Wize High School Grade 12 Chemistry Textbook > Organic Chemistry (Part 1: Functional Groups and Naming)

Naming Alkanes

Naming Alkanes

For alkanes the suffix (ending) is -ane
The root of the name indicates the number of carbon atoms in the longest straight chain in the molecule
IUPAC naming will always follow the general form: prefix + root + suffix
prefix=identifies side chains
root=identifies the number of carbon atoms in the main/parent chain
suffix=indicates the family of compounds to which it belongs

Ex. Image illustrating Naming Alkanes

butane hexane

We can also see branches in the chain:

An alkyl group is a hydrocarbon group derived from an alkane but has a hydrogen atom removed
These are often branches on organic molecules
ex. Methane is CH4, but when it is attached to the main chain of a molecule, we call this branch a methyl group -CH3
ex. Ethane is CH3CH3 , but when it is attached to the main chain of a molecule, we call this branch an ethyl group -CH2-CH3

Alkanes and Related Alkyl Groups

Rules for Naming Branched Alkanes

Wize Concept

1. Identify the longest carbon chain

2. Number the carbon atoms in the longest carbon chain starting from the end that is closest to the branches (we do this because we want the branches to have the lowest numbers possible)

3. Name each branch and identify its location on the parent chain.

4. Write the IUPAC name in the form (# of location)-(branch name)(parent chain)

5 . If there is more than 1 branch present, list the branches in alphabetical order. If there is more than one substituent of the same type, then we we combine them with a prefix such as di, tri, tetra (these prefixes don't affect alphabetical order). Each number is separated by a comma (,).

Note: When naming cyclic hydrocarbons, if the carbon atoms that form the ring structure are the parent chain, the prefix cyclo is added to the parent hydrocarbon name, name the substituted groups/branches as you would normally. If the ring is not the parent chain, it will be labelled as a branch (ex. 3-cyclopentylheptane indicates a cyclopentyl ring attached to the 3rd carbon in a chain of 7 carbons).

Ex. Name the following molecule:

3-ethylheptane

Ex. Name the following molecule:

3,6-dimethyl-4-propyloctane

Ex. Name the following molecule:

1-ethyl-1-methylcyclopentane

Name the following molecule:

Your answer

I don't know

Name the following molecule:

Your answer

I don't know

Mark Yourself Question

Grab a piece of paper and try this problem yourself.
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Draw the following molecules:

1. 3, 3, 5-trimethyloctane

2. 1, 1-diethylcyclohexane

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Extra Practice

Name the following compound

Hydrocarbon Nomenculature Problem 1

Name the following compound.

Name the following compound

,,,,-

Practice: Naming Hydrocarbons

Name the following compound.

Nomenclature: Hydrocarbons

Name the following compound.

Naming Alkanes

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Naming Alkanes

Rules for Naming Branched Alkanes

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Extra Practice

Practice: Naming Hydrocarbons