Triethanolamine
Triethanolamine, also known as trolamine or 2,2',2''-nitrilotriethanol, is a tertiary amine and triol with the molecular formula C6H15NO3 and IUPAC name 2-[bis(2-hydroxyethyl)amino]ethanol.[1] It appears as a colorless to pale yellow viscous liquid with a mild ammonia-like odor, is miscible in water, and has a boiling point of 335.4°C and a freezing point of 21.6°C.[1] This compound serves as a versatile industrial chemical, primarily used as an emulsifier, surfactant, and pH adjuster in cosmetics and personal care products, where it helps stabilize formulations and is deemed safe as used when formulated to be non-irritating.[2] In pharmaceuticals, it functions as an alkalizing agent and buffering agent, while in broader industrial applications, it is employed in textile processing, cement additives, herbicides, lubricants, and as an intermediate in the production of resins and plasticizers.[1] Annual production volume in the European Economic Area exceeds 100,000 tonnes, reflecting its widespread use across consumer, professional, and industrial sectors.[3] Triethanolamine exhibits low acute toxicity, with an oral LD50 in rats ranging from 4,190 to 11,260 mg/kg, but it is classified as a skin and eye irritant and suspected of damaging fertility based on regulatory assessments.[1][3] It is not classified as carcinogenic by the International Agency for Research on Cancer (Group 3), though exposure limits such as a threshold limit value of 5 mg/m³ (8-hour time-weighted average) are recommended to mitigate respiratory and dermal risks.[1] Environmentally, it shows moderate persistence in water but low bioaccumulation potential, with ecotoxicity data indicating an LC50 of 11.8 g/L for fathead minnows over 96 hours.[1]Structure and properties
Molecular structure
Triethanolamine, with the chemical formula \ce{C6H15NO3}, is commonly represented as \ce{N(CH2CH2OH)3} or \ce{(HOCH2CH2)3N}.[1] It is a tertiary amine derived from ammonia, where the central nitrogen atom is bonded to three 2-hydroxyethyl groups (\ce{-CH2CH2OH}), forming a structure with a single nitrogen atom connected via three C-N single bonds to the carbon chains, each terminating in a hydroxyl group.[1] This molecular arrangement can be visualized as a central N atom with three symmetric arms, each consisting of an ethylene bridge (\ce{-CH2-CH2-}) linked to an \ce{-OH} moiety.[1] In comparison to related ethanolamines, triethanolamine features full substitution on the nitrogen with three hydroxyethyl groups, whereas monoethanolamine (MEA, \ce{H2NCH2CH2OH}) has one such group and a primary amine, and diethanolamine (DEA, \ce{HN(CH2CH2OH)2}) has two with a secondary amine.[1][4][5] The tertiary amine functionality imparts basic properties by allowing the nitrogen to accept a proton, while the three hydroxyl groups contribute hydrophilic characteristics, enhancing interactions with water through hydrogen bonding.[6]Physical properties
Triethanolamine is a colorless to pale yellow viscous liquid at room temperature, exhibiting a mild ammoniacal odor.[1] It solidifies below its melting point of 21.6 °C, forming hygroscopic crystals, while boiling occurs at 335.4 °C under standard pressure.[1] The compound has a density of 1.124 g/mL at 20 °C and a dynamic viscosity of approximately 590 cP at 25 °C, contributing to its oily texture.[1] Its refractive index is 1.485 at 20 °C.[1] Triethanolamine is highly hygroscopic, readily absorbing moisture from the atmosphere, and remains stable under ambient conditions but may turn brown upon prolonged exposure to air and light.[1] It is miscible with water, ethanol, and acetone, enhancing its utility in aqueous and polar solvent systems, though solubility in non-polar solvents like benzene is limited to about 4.2 g/100 mL.[1]| Property | Value | Conditions |
|---|---|---|
| Density | 1.124 g/mL | 20 °C |
| Melting point | 21.6 °C | - |
| Boiling point | 335.4 °C | 760 mmHg |
| Dynamic viscosity | 590 cP | 25 °C |
| Refractive index | 1.485 | 20 °C |