Tetraethylammonium (TEA) is a quaternary ammonium cation with the chemical formula , consisting of four ethyl groups (, denoted Et) attached to a central nitrogen atom. It is a counterion used in the research laboratory to prepare lipophilic salts of inorganic anions. It is used similarly to tetrabutylammonium, the difference being that its salts are less lipophilic and more easily crystallized. Preparation The chloride salt is prepared by the reaction of triethylamine and an ethyl halide: Et3N + EtX -> Et4N+X- This method works well for the preparation of tetraethylammonium iodide (where X = I). Most tetraethylammonium salts are prepared by salt metathesis reactions. For example, the synthesis of tetraethylammonium perchlorate, a salt that has been useful as a supporting electrolyte for polarographic studies in non-aqueous solvents, is carried out by mixing the water-soluble salts tetraethylammonium bromide and sodium perchlorate in water, from which the water-insoluble tetraethylammonium perchlorate precipitates: Et4N+Br_{(aq)}- + Na+[ClO4]_{(aq)}- -> Na+Br_{(aq)}- + Et4N+[ClO4]_{(s)}- Other examples include tetraethylammonium cyanide (), and trichlorostannate (). In some cases, salts are produced of anions that cannot be generated in water, such as the tetrahedral salt. Uses The principal chemical characteristic of tetraethylammonium salts is their ability to engage in processes involving phase-transfer, such as phase-transfer catalysis. Typically, the four ethyl groups surrounding the nitrogen are too small to facilitate efficient ion transfer between aqueous and organic phases, but tetraethylammonium salts have been found to be effective in a number of such applications, and these are exemplified under the headings of the individual salts. TEA salts such as tetraethylammonium tetrafluoroborate and tetraethylammonium methylsulfonate are used in supercapacitors as organic electrolytes. TEA halide and its hydroxide are used for the synthesis of high-silica zeolite, especially for the zeolite beta. TEA can act as a template for micropore of zeolites under hydrothermal conditions during crystallization processes. Properties The effective radius of the tetraethylammonium ion is reported as ~0.45 nm, which is comparable in size to that of the hydrated ion. The ionic radius for TEA is given as 0.385 nm; several thermodynamic parameters for the TEA ion are also recorded. The octanol-water partition coefficient of TEA iodide, Po-w was determined experimentally to be (or ). Biology Pharmacology The literature dealing with the pharmacologically-related properties of tetraethylammonium is vast, and research continues. It is clear that TEA blocks autonomic ganglia - it was the first "ganglionic blocker" drug to be introduced into clinical practice. However,