Ethylammonium nitrate
Ethylammonium nitrate or ethylamine nitrate (EAN) is a salt with formula or ·. It is an odorless and colorless to slightly yellowish liquid with a melting point of 12 °C. This compound was described by Paul Walden
Paul Walden
Paul Walden was a Latvian-German chemist known for his work in stereochemistry and history of chemistry. In particular he invented the stereochemical reaction known as Walden inversion and synthesized the first room-temperature ionic liquid, ethylammonium nitrate.-Early years:Walden was born in...

 in 1914, and is believed to be the earliest reported example of a room-temperature ionic liquid
Ionic liquid
An ionic liquid is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as . While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ILs are largely made...


Synthesis and properties

Ethylammonium nitrate can be produced by heating ethyl nitrate
Ethyl nitrate
Ethyl nitrate has formula . It is used in organic synthesis and as an intermediate in the preparation of some drugs, dyes, and perfumes.Ethyl nitrate is found in the atmosphere, where it can react with other gases to form smog...

 with an alcoholic solution of ammonia or by reacting ethylamine
Ethylamine is an organic compound with the formula CH3CH2NH2. This colourless gas has a strong ammonia-like odor. It is miscible with virtually all solvents and is considered to be a weak base, as is typical for amines. Ethylamine is widely used in chemical industry and organic...

 with concentrated nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

. It has a relatively low viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 of 0.28 poise
The poise is the unit of dynamic viscosity in the centimetre gram second system of units. It is named after Jean Louis Marie Poiseuille ....

 or 0.028 Pa·s at 25 °C and therefore a high electrical conductivity of about 20 mS·cm−1 at 25 °C. It boils at 240 °C and decomposes at about 250 °C.

The ethylammonium ion has three easily detachable protons which are tetrahedrally arranged around the central nitrogen atom, whereas the configuration of the anion is planar. Despite the structural differences, EAN shares many properties with water, such as micelle
A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single tail regions in the micelle centre. This phase is...

 formation, aggregation of hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

s, negative enthalpy
Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...

 and entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

 of dissolution of gases, etc. Similar to water, EAN can form three-dimensional hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...

ing networks.


Ethylammonium nitrate is used as an electrically conductive solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 in electrochemistry
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...

 and as a protein crystallization agent. It has a positive effect on the refolding of denaturated
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...

Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between...

, with the refolding yield of about 90%. The refolding action was explained as follows: The ethyl group of ethylammonium nitrate interacts with the hydrophobic part of the protein and thereby protects it from intermolecular association, whereas the charged part of EAN stabilizes the electrostatic interactions.
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