Functional groups are special groups of atoms within molecules that give those molecules their characteristic chemical and physical properties. They act like the “reactive centers” of organic compounds. Here’s how they affect properties:
1. Determine Reactivity
Different functional groups decide how a compound will react in chemical reactions.
- Alcohols tend to undergo oxidation and substitution.
- Aldehydes and ketones are reactive towards nucleophiles.
- Carboxylic acids can lose a proton, making them acidic.
2. Influence Physical Properties
- Polarity: Groups like hydroxyl (–OH), carbonyl (C=O), or amine (–NH₂) make molecules polar, affecting solubility in water.
- Boiling and melting points: Molecules with hydrogen-bonding groups (like –OH or –NH₂) usually have higher boiling points.
3. Control Acidity or Basicity
- Carboxylic acids are acidic because they can donate a proton.
- Amines are basic because the nitrogen can accept a proton.
4. Affect Biological Activity
Functional groups determine how organic compounds interact in biological systems.
- The amide (peptide) bond links amino acids in proteins.
- Hydroxyl groups in sugars make them soluble and reactive.
5. Shape and Recognition
Some functional groups influence the shape of the molecule and how it is recognized by enzymes, receptors, or other molecules. This is crucial in drug design and biochemistry.
In short: functional groups act as the “personality” of an organic molecule, deciding how it behaves chemically, how it interacts physically, and how it functions in living systems.