Difference Between Protic and Aprotic Solvents

Key Difference – Protic vs Aprotic Solvents
 

The key difference between protic and aprotic solvents is that protic solvents have dissociable hydrogen atoms whereas aprotic solvents have no dissociable hydrogen atom.

A solvent is a liquid compound that can dissolve other substances. There are different forms of solvents that can be categorized basically into two group as polar and nonpolar solvents. The polar solvents can be divided into two groups as protic and aprotic solvents. Protic solvents can form hydrogen bond because they have chemical bonds required for the hydrogen bonding, i.e. O-H bond and N-H bond. In contrast, aprotic solvents lack those chemical bonds required for hydrogen bonding.

CONTENTS

1. Overview and Key Difference
2. What are Protic Solvents
3. What are Aprotic Solvents
4. Similarities Between Protic and Aprotic Solvents
5. Side by Side Comparison – Protic vs Aprotic Solvents in Tabular Form
6. Summary

What are Protic Solvents?

Protic solvents are polar liquid compounds that have dissociable hydrogen atoms. These solvents have many O-H bonds and N-H bonds. The dissociable hydrogen atoms are those that are bonded to oxygen atoms and nitrogen atoms in these O-H and N-H bonds. Therefore, hydroxyl groups (-OH) and amine groups (-NH₂) are essential components in protic solvents.

Protic solvents share ion dissolving power with aprotic solvents and are acidic (because they can release protons). The dielectric constant of these protic solvents is very high (dielectric constant is a property of electrical insulating materials and is a quantity measuring the ability of a substance to store electrical energy in an electric field).

Examples of protic solvents include water, alcohols such as methanol and ethanol, hydrogen fluoride (HF), and ammonia (NH₃). These solvents are often used to dissolve salts. Polar protic solvents prefer to undergo SN1 reactions.

What are Aprotic Solvents?

Aprotic solvents are polar liquid compounds that have no dissociable hydrogen atoms. These solvents lack chemical bods such as O-H bonds and N-H bonds. Hence, aprotic solvents lack hydroxyl groups (-OH) and amine groups (-NH₂) and are unable to form hydrogen bonds.

Aprotic solvents share ion dissolving power with protic solvents. These aprotic solvents lack acidic hydrogen, thus no considerable release of hydrogen ions. Polar aprotic solvents have low or intermediate dielectric constant values. These solvents show a moderate polarity.

Examples of aprotic solvents include dichloromethane (DCM), tetrahydrofuran (THF), ethyl acetate, and acetone. Aprotic solvents can be used to dissolve salts. These solvents prefer to undergo SN2 reactions.

What are the Similarities Between Protic and Aprotic Solvents?

• Both Protic and Aprotic Solvents are polar solvents.
• Both Protic and Aprotic Solvents solvents can dissolve salts.

What is the Difference Between Protic and Aprotic Solvents?

Summary – Protic vs Aprotic Solvents

Solvents are liquids that are capable of dissolving substances. Solvents can be found in two major forms as polar solvents and nonpolar solvents. Polar solvents can be again divided into two groups as protic solvents and aprotic solvents. The difference between protic and aprotic solvents is that protic solvents have dissociable hydrogen atoms whereas aprotic solvents have no dissociable hydrogen atom.

Reference:

1.“Polar Protic? Polar Aprotic? Nonpolar? All About Solvents.” Master Organic Chemistry RSS. Available here 
2.“Protic Solvent.” Wikipedia, Wikimedia Foundation, 17 Dec. 2017. Available here 
3.“Aprotic and Protic Solvents.” Scribd, Scribd. Available here