Question

How can I name alcohol functional groups?

Answer 1

To name an alcohol, you drop the final "-e" from the name of the parent alkane and add the ending "-ol". Then you use a number to locate the OH group.

The steps are:

1. Find the longest continuous chain that contains the OH group.

2. Name this chain. This gives you the root name.

3. Drop the final "-e" and add the ending "-ol".

4. Number the chain from the end closest to the OH group

5. Insert the number, surrounded by hyphens, just before the ending "-ol".

Example

What is the name of CH₃CH₂CH₂OH?

Solution

• The three carbon root name is propane.

• Drop the "-e" ending and add the "-ol" ending for an alcohol. This gives the name propanol.

• Insert the number that locates the OH group.

The OH group is on C-1. The name is propan-1-ol.

Note: 1-propanol is an accepted name, but the preferred IUPAC name has the locating number next to the "-ol" ending.

Note: You do not use a number when there is no other possible location for the OH group. Examples are methanol CH₃OH and ethanol CH₃CH₂OH.

In a cyclic alcohol, the carbon atom bearing the OH group is automatically number 1, so you do not insert the "1".

Thus, the compound below is 4-methylcyclohexanol.