tetraethylamino

Tetraethylamino is a term used to describe a chemical group derived from a quaternary ammonium center bearing four ethyl substituents. In practice, it most often refers to the tetraethylammonium cation, [Et4N]+, which forms salts with various anions such as chloride, bromide, iodide, or hydroxide. The neutral “tetraethylamino” fragment itself is not a stable, isolable free base; the commonly encountered species are the quaternary ammonium salts.

Structure and properties

The tetraethylammonium cation is a quaternary ammonium ion with four ethyl groups around a positively charged nitrogen. It is compactly arranged in a roughly tetrahedral geometry. The positive charge makes the salts highly soluble in water and polar solvents; the cation is bulky, which can influence crystallinity, melting points, and ion-pairing behavior in solutions. The accompanying anion can affect properties such as solubility, hygroscopicity, and conductivity.

Preparation

Tetraethylammonium salts are typically prepared by exhaustive alkylation of a tertiary amine, such as triethylamine, with an ethyl halide (for example, ethyl bromide or ethyl chloride). The reaction R3N + EtX yields the quaternary ammonium salt [R3NEt]+ X−. Purification usually involves crystallization or salt exchange to obtain the desired anion.

Applications

Tetraethylammonium salts are used as phase-transfer catalysts and as components of ionic liquids and electrolytes in electrochemical applications. In physiology and pharmacology, tetraethylammonium ions (TEA+) are known to block certain voltage-gated potassium channels and are used in experiments studying membrane physiology.

Safety

Quaternary ammonium salts can be irritants and may be harmful if ingested or inhaled. They can be toxic to aquatic life. Proper handling, ventilation, and personal protective equipment are advised, along with appropriate waste disposal.

See also

Tetraethylammonium fluoride, tetraethylammonium chloride, potassium channel blockers, phase-transfer catalysis.