Naming Haloalkanes (alkyl halides)

Key Concepts

Haloalkanes (alkyl halides) are alkanes in which one or more hydrogen atoms have been replaced with halogen (Group VII) atoms.
The name of a haloalkane is made up of two parts:
(1) a prefix containing the name and numbers of halogen atoms
(2) a suffix containing the name of the longest carbon chain.
When writing the name of a haloalkane:
commas (,) are used to separate numbers, eg, 1,2 or 2,3
hyphens (-) are used to separate numbers and letters, eg, 1-chloro and 1,2-dichloro

To name a haloalkane:

Name the longest carbon chain as for branched chain alkanes.
Carbon atoms bonded to halogen atoms are given the lowest possible numbers.
Halogens are named before alkyl groups :
fluorine atom is named as fluoro
chlorine atom is named as chloro
bromine atom is named as bromo
iodine atom is named as iodo
For more than one of the same halogen:
di = 2
tri = 3
tetra = 4
For more than one type of halogen, name them alphabetically: bromo named before chloro named before fluoro named before iodo

1. Name the molecule shown below:

Number and name the longest carbon chain containing the halogen:

A carbon chain containing 3 carbon atoms and only single bonds between the carbon atoms is named propane.

F is a fluorine atom and is named as fluoro.
It is attached to the second carbon atom in the propane chain so the prefix for the name is 2-fluoro

Assemble the name by attaching the prefix to the name of the longest carbon chain.
The name of this molecule is 2-fluoropropane.

2. Name the molecule shown below:

Number and name the longest carbon chain containing the halogen:

A carbon chain containing 3 carbon atoms and only single bonds between the carbon atoms is named propane.

Identify and name the halogens:

Two fluorine atoms are present, the name will include the prefix difluoro

Choose the numbered carbon chain that gives the two fluorine atoms the lowest number combination:
Numbering from left to right ,green numbers, gives the fluorine atoms numbers 1 and 2.
Numbering from right to left ,pink numbers, gives the fluorine atoms numbers 2 and 3.
Choose the lowest number combination, ie, 1 and 2.
The prefix for the name of the molecule becomes 1,2-difluoro
Assemble the name by adding the prefix to the name of the longest carbon chain.
The name of the molecule is 1,2-difluoropropane

3. Name the molecule shown below:

F
| Cl
| H
|

H- C - C - C -H

|
H |
H |
H

Number and name the longest carbon chain containing the halogens:

A carbon chain containing 3 carbon atoms and only single bonds between the carbon atoms is named propane.

Identify and name the halogens:

The molecule contains a fluorine atom, F, prefix is fluoro
The molecule contains a chlorine atom, Cl, prefix is chloro

Choose the numbered carbon chain that gives the two halogen atoms the lowest number combination:
Numbering from left to right ,green numbers, gives the fluorine atom number 1 and the chlorine atom 2.
Numbering from right to left ,pink numbers, gives the clorine atom number 2 and the fluororine atom 3.
Choose the lowest number combination, ie, 1-fluoro and 2-chloro.
When more than one type of halogen atom is present, the halogens are named alphabetically:
the "c" of chloro occurs before the "f" of fluoro in the alphabet so chloro is named before fluoro.
The prefix for this molecule is 2-chloro-1-fluoro
Assemble the name by adding the prefix to the name of the longest carbon chain.
The name of the molecule is 2-chloro-1-fluoropropane.