The key difference between polar and nonpolar solvents is that polar solvents dissolve polar compounds, whereas nonpolar solvents dissolve nonpolar compounds.
The polarity of a compound refers to the property of having poles. In chemistry, it is the charge separation in a molecule that has atoms or groups of atoms with different electronegativity. Thus, it results in a partial positive charge and a partial negative charge in the same compound.
CONTENTS
1. Overview and Key Difference
2. What are Polar Solvents
3. What are Nonpolar Solvents
4. Side by Side Comparison – Polar vs. Nonpolar Solvents in Tabular Form
5. Summary
What are Polar Solvents?
Polar solvents are liquids that have a large dipole moment. These are liquids that can dissolve polar compounds. It is because both polar solvents and polar compounds have dipole moments and have oppositely charged moieties in the same chemical compound. The positively charged moiety of a solid compound can be attracted by the negatively charged moiety of a solvent molecule and vice versa, which can lead to the dissolution of the polar compound in the polar solvent.
The polarity of the solvent arises due to the connectivity of atoms with different electronegativity values to form the molecule. Here, the more electronegative atom attracts the bond electron pairs, which eventually gives the less electronegative atom a partial positive charge due to the reduction of electron density around itself. On the other hand, the more electronegative atom gets a partial negative charge since the electron density around this atom increases.
The most common example of a polar solvent is water. A water molecule has two O-H bonds. The difference in electronegativity between the oxygen atom and hydrogen atom is considerably high. Therefore, it is a polar covalent bond. The oxygen atom is more electronegative. Hence, the oxygen atom gets a partial negative charge while two hydrogen atoms get a partial positive charge.
Figure 01: Water is a Polar Solvent
Furthermore, we can divide the polar solvents into two groups as polar protic solvents and polar aprotic solvents. The polar protic solvents contain labile H+ ions. This means the molecules of these solvents can donate hydrogen atoms. However, polar aprotic solvents cannot donate hydrogen atoms.
What are Nonpolar Solvents?
Nonpolar solvents are liquids that have no dipole moment. Therefore, these solvents do not contain partial positive or negative charges. Due to this reason, these solvents cannot dissolve polar compounds because there are no opposite charges to attract the polar compound.
Figure 02: Hexane is a Nonpolar Solvent
Nonpolar solvents can dissolve nonpolar compounds via attraction forces, such as Van der Waal forces. Some examples of nonpolar solvents include pentane, hexane, benzene, toluene, etc.
What is the Difference Between Polar and Nonpolar Solvents?
We can mainly divide solvents into two categories as polar solvents and nonpolar solvents. The key difference between polar and nonpolar solvents is that the polar solvents dissolve polar compounds, whereas nonpolar solvents dissolve nonpolar compounds. Besides that, another significant difference between polar and nonpolar solvents is that the polar solvents have a high dipole moment, while the nonpolar solvents do not have a dipole moment. A common example of a polar solvent is water. Some examples of nonpolar solvents include pentane, hexane, benzene, toluene, etc.
Moreover, polar solvents have molecules with polar bonds (these bonds show electrical charge separation due to the differences in electronegativity of the atoms in the bond). Nonpolar solvents have molecules containing chemical bonds made out of atoms having nearly similar electronegativity values.
Summary – Polar vs. Nonpolar Solvents
We can divide solvents mainly into two categories as polar solvents and nonpolar solvents. The key difference between polar and nonpolar solvents is that polar solvents dissolve polar compounds, whereas nonpolar solvents dissolve nonpolar compounds.
Reference:
1. “Polar Solvent.” Wikipedia, Wikimedia Foundation, 17 Oct. 2019, Available here.
Image Courtesy:
1. “Water Texture” By Heath Alseike (CC BY 2.0) via Flickr
2. “N-Hexane by Danny S. – 001” By Danny S. – Own work (CC BY-SA 3.0) via Commons Wikimedia