Naming aldehydes and ketones
In the IUPAC system we use the -al ending. The end e is replaced by al.
So the common names of the first four aldehydes become:
Methanal
Ethanal
Propanal
Butanal

Now this is all pretty simple, but what if there are side chains off the main aldehyde chain. For example, take the molecule pictured on the right.

Step 1 The aldehyde forms the root name

Step 2 Number the carbons so that the C=O is carbon number 1.

Step 3 Name all the substituents in alphabetical order.

3-methylbutanal

 
Consider the example shown on the right. It has two substituent groups, the methyl and hydroxy. The IUPAC name is 4-hydroxy-3-methylbutanal.
Name the following molecules  
Solution
Solution
Naming ketones  
When naming a ketone we remove the end "e" from the name and replace it with a "one". For example propane becomes propanone. Since the carbonyl group can be located anywhere in the carbon chain a locator number is needed. .

With simple molecules, such as propanone, shown on the right, a number is not needed as there can be only one location for the carbonyl group.

Now lets look at he steps to derive a IUPAC name.

Step 1) Identify the longest carbon chain that contains the carbonyl group and number the carbons so that the carbonyl group is on the lowest carbon.

Step 2) Identify the various substituent groups

Step 3) Place the substituent groups in the name in alphabetical order and use position numbers to locate the substituent groups and the carbonyl group.

Step 4) Change the end e to a one.

Lets take the molecule shown on the right as an example.
Step 1 The longest carbon chain is pentane
Step 2 No substituent groups
Step 3 and 4 The carbonyl group is found at carbon number 2 .
Hence the name is 2-pentanone

What is the IUPAC name of this molecule?

Solution

What is the IUPAC name of this molecule?

Solution

 

What is the IUPAC name of this molecule?

Solution

What is the IUPAC name of this molecule?

Solution