Tetraethylene

Tetraethylene, in chemical usage, most often refers to tetraethylene glycol, a polyether diol in the polyethylene glycol (PEG) family with four repeating ethylene oxide units. Its structure is HO-(CH2-CH2-O-)4-H, giving it two terminal hydroxyl groups that confer high polarity and hydrophilicity. The term is sometimes used loosely to describe other four-unit oligomers in the PEG series, but tetraethylene glycol is the most common specific compound.

Production and properties-synthesis: Tetraethylene glycol is produced by controlled polymerization of ethylene oxide, typically starting from a diol initiator to yield a defined oligomer with four repeating units. It is a colorless to pale liquid at room temperature, with high water miscibility and relatively low volatility. Its physical properties, such as viscosity and boiling point, increase with longer chain length, and tetraethylene glycol is more viscous than ethylene glycol or diethylene glycol.

Applications: The compound is used as a solvent and humectant in cosmetics, pharmaceuticals, and personal care products due to its moisture-retaining properties and ability to dissolve a wide range of substances. It serves as a plasticizer in certain polymers and as an intermediate in resin or polymer synthesis. It can also function as a heat-transfer fluid component and as a solvent for analytical and industrial chemical processes.

Safety and handling: Tetraethylene glycol generally exhibits low acute toxicity but can cause irritation to skin and eyes upon exposure. It should be stored in a cool, well-ventilated place away from oxidizers and handled with appropriate personal protective equipment to minimize exposure. Proper disposal follows local environmental and safety regulations.

Other uses of the term: In some contexts, tetraethylene may be used imprecisely to refer to other four-ethylene compounds, such as tetraethylene diamine or tetraethylene pentamine, which are distinct chemicals with separate properties and applications. See also polyethylene glycol and related oligomers.