- Functional groups are specific groupings of atoms
- Identifying the functional groups in a molecule can help us predict its reactivity
The following is a list of the most common functional groups. You should memorize the entire list and be able to both name a functional group given a structure and provide a structure given the name of a functional group. Note that acyl halides and acid anhydrides are included here since you will encounter them if you take further chemistry courses, but identifying and naming molecules containing these functional groups is beyond the scope of CHEM 123.
Functional groups serve as the basis of reactivity in organic chemistry and, therefore, it is critical that you are able to identify them in a variety of different settings. It is easiest to identify functional groups in small molecules as they are not obscured by the rest of the molecule. For example, it is straight-forward to identify the carboxylic acid in the molecule below. Note that the entire group is called a carboxylic acid and it is not a ketone and an alcohol.
It gets a little bit more complicated to identify functional groups in larger molecules, such as in strychnine (pictured below). Make sure you check the connectivity to the heteroatoms to correctly identify the functional group. For example, the nitrogen at the top (highlighted in blue) is connected to three alkyl groups. This functional group is called an amine. The lower nitrogen (highlighted in red) is connected to a carbon, which in turn has a double bond to an oxygen (called a carbonyl). This functional group is called an amide.
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