Why do functional groups create sites of reactivity in molecules?

Functional groups create sites of reactivity in molecules because they have specific chemical properties that influence the molecule's behaviour.

Functional groups are groups of atoms within a molecule that have specific chemical properties. They are the active parts of the molecule that participate in chemical reactions. These groups are often the site of reactivity in a molecule because their properties can influence the behaviour of the entire molecule.

For example, the hydroxyl group (-OH) is a common functional group found in many organic compounds. This group is polar, meaning it has a slight negative charge at the oxygen end and a slight positive charge at the hydrogen end. This polarity makes the hydroxyl group reactive, as it can form hydrogen bonds with other molecules or ions.

Similarly, the carbonyl group (C=O) is another common functional group. The double bond between the carbon and oxygen atoms makes this group highly reactive. The oxygen atom is more electronegative than the carbon atom, meaning it pulls electrons towards itself, creating a polar bond. This polarity can cause the carbonyl group to react with other molecules or ions.

In essence, the presence of functional groups in a molecule creates sites of reactivity because these groups have specific chemical properties. These properties can influence how the molecule interacts with other molecules or ions, often making the molecule more reactive. Therefore, understanding the properties of different functional groups can help predict the reactivity of a molecule and the types of reactions it may undergo.