Hexane, a hydrocarbon with the chemical formula C6H14, is insoluble in water due to its non-polar nature. To understand why hexane is insoluble, it is important to delve into the concept of polarity and intermolecular forces.
Polarity refers to the distribution of electrical charge within a molecule. Water is a polar molecule, meaning it has a partial positive charge on one end (the hydrogen atoms) and a partial negative charge on the other (the oxygen atom). This polarity allows water molecules to attract and interact with each other through hydrogen bonding, which is a strong intermolecular force.
On the other hand, hexane is a non-polar molecule. It consists of only carbon and hydrogen atoms, and the distribution of electrical charge within the molecule is relatively uniform. As a result, there are no significant partial positive or negative charges on different ends of the molecule. Non-polar molecules like hexane do not exhibit hydrogen bonding or other strong intermolecular forces that can interact with water molecules.
When hexane is mixed with water, the polar water molecules tend to interact with each other through hydrogen bonding, forming a network of intermolecular attractions. Hexane, being non-polar, cannot form hydrogen bonds with water molecules. Instead, it experiences weak dispersion forces, also known as London dispersion forces or van der Waals forces.
Dispersion forces arise due to temporary fluctuations in electron distribution within molecules, creating temporary dipoles. These temporary dipoles induce dipoles in neighboring molecules, leading to weak attractive forces between them. While dispersion forces are present in all molecules, they are generally weaker than hydrogen bonding.
Due to the relatively weak dispersion forces in hexane, they are unable to overcome the strong hydrogen bonding between water molecules. As a result, hexane molecules do not mix or dissolve in water. Instead, hexane forms separate layers or droplets in water, with minimal interaction between the two substances.
To visualize this, imagine oil floating on the surface of water. Hexane behaves similarly because both oil and hexane are non-polar substances that do not mix with water. This phenomenon is commonly observed when oil spills occur in bodies of water, where the oil forms a distinct layer on the water’s surface.
Hexane is insoluble in water due to its non-polar nature. The absence of significant partial charges within the hexane molecule prevents it from forming hydrogen bonds with water molecules. Instead, hexane experiences weak dispersion forces, which are insufficient to overcome the strong hydrogen bonding between water molecules.