The key difference between deep eutectic solvents and ionic liquids is that deep eutectic solvents are formed from Lewis or Bronsted acids and bases, whereas ionic liquids form from any salt.
Both deep eutectic solvents and ionic liquids are liquid states of ionic mixtures where we can observe both cations and anions. These two ionic states are different from each other according to the source of ions that make up those mixtures.
CONTENTS
1. Overview and Key Difference
2. What are Deep Eutectic Solvents
3. What are Ionic Liquids
4. Similarities – Deep Eutectic Solvents and Ionic Liquids
5. Deep Eutectic Solvents vs Ionic Liquids in Tabular Form
6. Summary – Deep Eutectic Solvents vs Ionic Liquids
What are Deep Eutectic Solvents?
Deep eutectic solvents are mixtures formed from Lewis or Bronsted acids and bases. These are eutectic solvents, meaning homogenous mixtures of substances that can melt or solidify at a single temperature (This temperature is usually lower than the melting point of any of the constituents in the mixture). Typically, deep eutectic solvents contain a wide variety of anionic and cationic species.
Different Types of Deep Eutectic Solvents
There are different types of deep eutectic solvents that we categorize based on the ionic solvent properties that are specific to the solvent. The first generation of this type of solvents were the mixtures of quaternary ammonium salts. These solvents contain hydrogen bond donors, e.g. amines and carboxylic acids. We can identify 4 different types of deep eutectic solvents: type I, type II, type III, and type IV. Among these four types, type I deep eutectic solvents contain quaternary ammonium salt along with a metal chloride. Therefore, these solvents also include a wide range of chlorometallate ionic liquids. The type II deep eutectic solvents contain a metal chloride hydrate along with the quaternary ammonium salt. The third is type III deep eutectic solvent, where there is quaternary ammonium salt along with a hydrogen bond donor. Finally, the type IV deep eutectic solvents contain metal chloride hydrate and a hydrogen bond donor (no quaternary ammonium salts). These types of deep eutectic solvents are important because these solvents can produce cationic metal complexes, which ensure the double layer close to the electrode surface that has a high metal ion concentration.
Compared to volatile organic compounds, deep eutectic solvents have a very low vapor pressure. Therefore, these solvents are typically flammable. Moreover, these solvents have a high viscosity that can hinder industrial applications because these solvents may not flow easily in process streams.
What are Ionic Liquids?
Ionic liquids are salts in the liquid state. Typically, ionic liquids are primarily made of ions except for some ordinary ionic liquids such as water, where there are electrically neutral molecules. There are some common synonyms for ionic liquids, which include liquid electrolytes, ionic melts, ionic fluids, fused salts, liquid salts, and ionic glasses.
There are different applications of ionic liquids, which include using them as powerful solvents and as electrolytes. These types of liquids are useful in producing electric batteries and are also useful in sealant production because of the very low vapor pressure.
The salts that can undergo melting without decomposition or vaporization usually give an ionic liquid. In contrast, when we are cooling an ionic liquid, we can often get an ionic solid that is either crystalline or glassy. This happens because of the strength of ionic bonds in ionic solids/ liquids, which leads the ionic liquids to have high lattice energies.
What are the Similarities Between Deep Eutectic Solvents and Ionic Liquids?
- Deep eutectic solvents and ionic liquids are liquid states.
- Both are mixtures of anions and cations.
What is the Difference Between Deep Eutectic Solvents and Ionic Liquids?
Both deep eutectic solvents and ionic liquids are liquid states of ionic mixtures where we can observe both cations and anions. The key difference between deep eutectic solvents and ionic liquids is that deep eutectic solvents are formed from Lewis or Bronsted acids and bases, whereas ionic liquids form from any salt.
The following table summarizes the difference between deep eutectic solvents and ionic liquids.
Summary – Deep Eutectic Solvents vs Ionic Liquids
Both deep eutectic solvents and ionic liquids are liquid states of ionic mixtures where we can observe both cations and anions. The key difference between deep eutectic solvents and ionic liquids is that deep eutectic solvents are formed from Lewis or Bronsted acids and bases, whereas ionic liquids form from any salt.
Reference:
1. “Ionic Liquid.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Ionic liquids” By Oak Ridge National Laboratory (CC BY 2.0) via Flickr