Benzotriazole

Benzotriazole features two fused rings. It can in principle exist as tautomers, but X-ray crystallography establishes the structure with hydrogen at the 1 position. The and distances are and . : ==Reactions==

Acid-base behavior BTA is a weak Bronsted acid with a . In some complexes, BTA binds metals as its conjugate base forming polymers and oligomers. It binds to copper surfaces, serving as a corrosion inhibitor. N-alkylation : Deprotonation of BTA followed by treament with alkyl halides gives a mixture of 1- and 2-alkyl derivatives. Aromatic aldehydes (ArCHO) in the presence of ethanol gives benzotriazole-based N,O-acetals: : These acetals are susceptible to deprotonation, giving access to acylsilanes and acylboranes. N-amination of BTA with hydroxylamine-O-sulfonic acid gives 1-aminobenzotriazole. Oxidation of this amine with lead(IV) acetate affords benzyne, which rapidly dimerises to biphenylene. : ==Applications==

Benzotriazole has been used as a restrainer (or anti-fogging agent) in photographic emulsions or developing solutions, and as a reagent for the analytical determination of silver. More importantly, it has been extensively used as a corrosion inhibitor in the atmosphere and underwater. BTA can be used as antifreezes, heating and cooling systems, hydraulic fluids, and vapor-phase inhibitors as well. Corrosion inhibition Benzotriazole is an corrosion inhibitor for non-ferrous metals like copper and silver. BTA is used in heritage conservation, notably for the treatment of bronze disease, and in dishwashing detergents for silver protection. from benzotriazolate and copper(I), the active ingredient in the BT-derived corrosion inhibition ==Environmental relevance==

Benzotriazole is fairly water-soluble, is not readily degraded, and has a limited sorption tendency. It is only partly removed in wastewater treatment plants and a substantial fraction reaches surface water such as rivers and lakes. It is of low toxicity and a low health hazard to humans although exhibiting some antiestrogenic properties. Benzotriazole (and tolyltriazole) is a common "polar organic persistent pollutant", often detected at . One source of this pollution is their use as deicing agents in airports. Another source is dishwasher detergents, and some manufacturers are moving away from Benzotriazole to address pollution concerns. ==Benzotriazole derivatives==

Many modifications of benzotriazole have been reported. Alizapride is a commercial drug containing a benzotriazole ring system. Tolyltriazole is a mixture of isomers or congeners that differ from benzotriazole by the addition of one methyl group attached somewhere on the benzene ring. Tolyltriazole has similar uses, but has higher solubility in some organic solvents. ==References==