Ethanolamine

ETA molecules are a component in the formation of cellular membranes and are thus a molecular building block for life. Ethanolamine is the second-most-abundant head group for phospholipids, substances found in biological membranes (particularly those of prokaryotes); e.g., phosphatidylethanolamine. It is also used in messenger molecules such as palmitoylethanolamide, which has an effect on CB1 receptors.^[11]

ETA was thought to exist only on Earth and on certain asteroids, but in 2021 evidence was found that ETA molecules exist in interstellar space.^[12]

Ethanolamine is biosynthesized by decarboxylation of serine:^[13]

HOCH
₂CH(CO
₂H)NH
₂ → HOCH
₂CH
₂NH
₂ + CO₂

Derivatives of ethanolamine are widespread in nature; e.g., lipids, as precursor of a variety of N-acylethanolamines (NAEs), that modulate several animal and plant physiological processes such as seed germination, plant–pathogen interactions, chloroplast development and flowering,^[14] as well as precursor, combined with arachidonic acid C
₂₀H
₃₂O
₂ 20:4, ω-6), to form the endocannabinoid anandamide (AEA: C
₂₂H
₃₇NO
₂; 20:4, ω-6).^[15]

ETA is biodegraded by ethanolamine ammonia-lyase, a B12-dependent enzyme. It is converted to acetaldehyde and ammonia via initial H-atom abstraction.^[16]

H₂NCH₂CH₂OH → NH₃ + CH₃CHO

Monoethanolamine is produced by treating ethylene oxide with aqueous ammonia; the reaction also produces diethanolamine and triethanolamine. The ratio of the products can be controlled by the stoichiometry of the reactants.^[17]

MEA is used as feedstock in the production of detergents, emulsifiers, polishes, pharmaceuticals, corrosion inhibitors, and chemical intermediates.^[9]

For example, reacting ethanolamine with ammonia gives ethylenediamine, a precursor of the commonly used chelating agent, EDTA.^[17]

Monoethanolamines can scrub combusted-coal, combusted-methane and combusted-biogas flue emissions of carbon dioxide (CO₂) very efficiently. MEA carbon dioxide scrubbing is also used to regenerate the air on submarines.

Solutions of MEA in water are used as a gas stream scrubbing liquidinamine treaters.^[18] For example, aqueous MEA is used to remove carbon dioxide (CO₂) and hydrogen sulfide (H₂S) from various gas streams; e.g., flue gas and sour natural gas.^[19] The MEA ionizes dissolved acidic compounds, making them polar and considerably more soluble.

MEA scrubbing solutions can be recycled through a regeneration unit. When heated, MEA, being a rather weak base, will release dissolved H₂S or CO₂ gas resulting in a pure MEA solution.^[17][20]

In pharmaceutical formulations, MEA is used primarily for buffering or preparation of emulsions. MEA can be used as pH regulator in cosmetics.^[21]

It is an injectable sclerosant as a treatment option of symptomatic hemorrhoids. 2–5 ml of ethanolamine oleate can be injected into the mucosa just above the hemorrhoids to cause ulceration and mucosal fixation thus preventing hemorrhoids from descending out of the anal canal.

It is also an ingredient in cleaning fluid for automobile windshields.^[22]

Ethanolamine is often used for alkalinization of water in steam cycles of power plants, including nuclear power plants with pressurized water reactors. This alkalinization is performed to control corrosion of metal components. ETA (or sometimes a similar organic amine; e.g., morpholine) is selected because it does not accumulate in steam generators (boilers) and crevices due to its volatility, but rather distributes relatively uniformly throughout the entire steam cycle. In such application, ETA is a key ingredient of so-called "all-volatile treatment" of water (AVT).^{[citation needed]}

Upon reaction with carbon dioxide, 2 equivalents of ethanolamine react through the intermediacy of carbonic acid to form a carbamate salt,^[23] which when heated reforms ethanolamine and carbon dioxide.

• Process technology to produce ethanolamines by reaction of ammonia and ethylene oxide
• CDC - NIOSH Pocket Guide to Chemical Hazards