Functional group
A functional group is a small group of atoms in an organic molecule that decides how it reacts. Molecules with the same group react in similar ways, whatever the rest of the molecule looks like.
Last updated
Analogy
Like the handle on a tool: a screwdriver or a hammer may differ, but the handle tells you how to hold it.
Example
C=C: alkene C≡C: alkyneR–OH: alcohol R–O–R: etherR–C(=O)–R: ketone R–CHO: aldehydeR–COOH: acid R–NH₂: amine
In practice
The OH group makes ethanol an alcohol, and the COOH group makes acetic acid an acid.
Practice
Flashcards
- What is a functional group?A group of atoms that decides how an organic molecule reacts.
Questions people ask
How do I find the functional group in a molecule?
Look for atoms other than carbon and hydrogen, and for double or triple bonds. An O attached to H is an alcohol. A C=O with two carbons attached is a ketone. A C=O with an OH attached is a carboxylic acid. Use a table to match each pattern.
Why does the functional group matter more than the carbon chain?
The carbon chain is mostly unreactive C–C and C–H bonds. The functional group has polar bonds, lone pairs or pi bonds that attract other reagents. So most reactions happen at the functional group, and the rest of the molecule only changes the details.