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any of three amino alcohols with the general formula RR′NCH2CH2OH—namely, monoethanolamine (also known as colamine; R = R′ = H), diethanolamine (R = H, R′ = CH2CH2OH), and triethanolamine (R = R′ = CH2CH2OH). These three alcohols have boiling points of 171°, 271°, and 360°C and densities (at 20°C) of 1.0179, 1.0919, and 1.1258 g/cm3, respectively.
Ethanolamines are usually produced by reacting concentrated ammonia with ethylene oxide and fractionating the mixture to separate the three types of ethanolamines. All three are viscous, hygroscopic liquids that readily dissolve in water, ethanol, and chloroform. They are weak bases. Monoethanolamine and diethanolamine are used as easily regenerated absorbing agents for acidic gases, such as carbon dioxide, sulfur dioxide, and hydrogen sulfide. Triethanolamine is used as an inhibitor of corrosion and an antifreeze additive. Upon reaction with aliphatic carboxylic acids, ethanolamines yield surfactants (emulsifiers and detergents). Ethanolamines are also used for softening and finishing leather, and they serve as intermediates in the synthesis of drugs, insecticides, and preservatives. Certain derivatives of ethanolamines are common in nature; choline is one example.