What role do functional groups play in organic molecules?

Functional groups are specific groups of atoms within organic molecules that are responsible for the characteristic chemical reactions of those molecules. Their presence significantly influences both the reactivity of the molecule and various properties, such as polarity, solubility, and boiling point. Different functional groups interact with other substances in distinct ways, thereby determining how they behave chemically. For instance, a hydroxyl group (-OH) will make a molecule more polar and increase its solubility in water compared to a hydrocarbon structure, which is nonpolar.

In contrast, while molecular weight can be influenced by the presence of different functional groups, it is not the primary role of these groups. Functional groups are also not limited to influencing just boiling points; they significantly affect many properties and reactions of the entire molecule. Lastly, asserting that functional groups have no effect on the properties of molecules is incorrect, as it overlooks their fundamental role in dictating how molecules interact in chemical reactions and their physical characteristics.