Difference Between Van der Waals and Hydrophobic Interactions

The key difference between Van der Waals and hydrophobic interactions is that Van der Waals interactions are attraction forces between non-polar molecules, whereas hydrophobic interactions are repulsion forces between water molecules and other molecules.

There are four major types of chemical bonds: covalent bonds, ionic bonds, hydrogen bonds and Van der Waal interactions. In addition to these, we can observe interaction forces between water molecules and other molecules named as hydrophilic interactions and hydrophobic interactions.

CONTENTS

1. Overview and Key Difference
2. What are Van der Waals Interactions 
3. What are Hydrophobic Interactions 
4. Side by Side Comparison – Van der Waals vs Hydrophobic Interactions in Tabular Form
5. Summary

What are Van der Waals Interactions?

Van der Waals interactions are chemical bonds between non-polar molecules. These interactions are a type of noncovalent bond. They are weak attraction forces between two atoms in two non-polar molecules. A Van der Waals interaction is either an induced attraction or repulsion which is caused by correlations in the fluctuating polarizations of nearby particles.

Van der Waals forces occur mainly between symmetric molecules such as hydrogen molecules and carbon dioxide molecules. An interaction forms between two opposite charges: positive and negative charges. In non-polar molecules, there are no charge separations, so these molecules tend to have induced charges on them which makes an induced dipole. When two molecules come close to each other, the electron cloud of one molecule repels the electron cloud of the other molecule, applying a slight positive charge on that molecule. Then this positive charge attracts the negatively charged electron cloud of close by molecule. This is a weak interaction force.

What are Hydrophobic Interactions?

Hydrophobic Interactions are repulsion forces between water molecules and other substances. It is the interaction type opposite to the hydrophilic interaction (attraction force between water molecules and other substances). In this term, hydro” means “water” and “phobic” means “fear”. Therefore, we can name substances that do not like water as hydrophobic substances. These substances repel water molecules. Generally, non-polar molecules show this type of interactions because water molecules are polar. In other words, hydrophobic substances tend to attract or interact with or dissolve in non-polar substances such as oil and hexane.

Sometimes, hydrophobic substances are named as lipophilic substances because these substances attract lipid or fat components. When a hydrophobic substance is added to water, the substance’s molecules tend to form clumps by combining with each other. This makes hydrophobic solvents important in separating non-polar compounds from water or polar solutions.

What is the Difference Between Van der Waals and Hydrophobic Interactions?

Van der Waals forces and hydrophobic interactions are two different types of chemical bonds. The key difference between Van der Waals and hydrophobic interactions is that Van der Waals interactions are attraction forces between non-polar molecules, whereas hydrophobic interactions are repulsion forces between water molecules and other molecules. In Van der Waals interactions, one molecule gets an induced positive charge while other molecule gets an induced negative charge while there is no charge separation in hydrophobic interactions.

Below is a summary of the difference between Van der Waals and hydrophobic interactions in tabular form.

Summary – Van der Waals vs Hydrophobic Interactions

Van der Waals forces and hydrophobic interactions are two different types of chemical bonds. The key difference between Van der Waals and hydrophobic interactions is that Van der Waals interactions are attraction forces between non-polar molecules, whereas hydrophobic interactions are repulsion forces between water molecules and other molecules.

Reference:

1. “Van Der Waals Forces.” Chemistry LibreTexts, Libretexts, 15 Aug. 2020, Available here.

Image Courtesy:

1. “VanderWaals forze attrattive” By Users Biopresto, Paginazero, Marc Lagrange on it.wikipedia Shizhao – Own work (CC BY-SA 3.) via Commons Wikimedia

2. “Water drop on a leaf” By photo taken by Flickr user tanakawho – Flickr (CC BY 2.0) via Commons Wikimedia