Benzotriazole - Wikipedia

Benzotriazole Names Preferred IUPAC name 1H-1,2,3-Benzotriazole Other names 1H-Benzotriazole; 1,2,3-Benzotriazole; BTA; BtaH Identifiers

• 95-14-7 Y

3D model (JSmol) ChEBI

• CHEBI: N

ChEMBL

• ChEMBL Y

ChemSpider

•  Y

ECHA InfoCard 100.002.177 EC Number

• 202-394-1

PubChem CID RTECS number

• DM

UNII CompTox Dashboard (EPA)

• InChI=1S/C6H5N3/c1-2-4-6-5(3-1)7-9-8-6/h1-4H,(H,7,8,9) YKey: QRUDEWIWKLJBPS-UHFFFAOYSA-N Y
• InChI=1/C6H5N3/c1-2-4-6-5(3-1)7-9-8-6/h1-4H,(H,7,8,9)Key: QRUDEWIWKLJBPS-UHFFFAOYAH

• n1c2ccccc2[nH]n1

Properties C6H5N3 Molar mass 119.127 g·mol−1 Appearance White solid Density 1.369 g/cm3[1] Melting point 100 °C (212 °F; 373 K)[2] Boiling point 350 °C (662 °F; 623 K)[2] 20 g/L[2] Acidity (pKa) 8.2[3][4] Basicity (pKb) > 14[4] Hazards GHS labelling: Warning H302, H319, H332, H411, H412 P261, P264, P270, P271, P273, P280, P301+P312, P304+P312, P304+P340, P305+P351+P338, P312, P330, P337+P313, P391, P501 Related compounds Related compounds Benzimidazole, Tolyltriazole Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N   (what is YN ?) Chemical compound

Benzotriazole (BTA) is a heterocyclic compound with the chemical formula C6H4N3H. It can be viewed as the fusion of a benzene and triazole rings. It is a white solid, although impure samples can appear tan. It is used as a corrosion inhibitor for copper.[5]

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Structure and synthesis

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Benzotriazole features two fused rings. It can in principle exist as tautomers, but X-ray crystallography establishes the depicted structure. The N=N and HN-N distances are 1.306 and 1.340 Å.[1]

Benzotriazole can be prepared by the monodiazotization of o-phenylenediamine using sodium nitrite and acetic acid.[6][7][8]

Reactions

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Acid-base behavior

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BTA is a weak Bronsted acid with a pKa = 8.2.[3] It is a weak Brønsted base, as indicated by the low pKa < 0 of its conjugate acid, [HBTA]+.[4]

It is also a Lewis base, binding Lewis acids at the C-N=N center. A variety coordination complexes are known such as the tetrahedral 2:1 derivative with zinc chloride, ZnCl2(BTA)2.[9] In some complexes, BTA binds metals as its conjugate base forming polymers and oligomers.[10] It binds to copper surfaces, serving as a corrosion inhibitor.[11]

N-alkylation

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Deprotonation of BTA followed by treament with alkyl halides gives a mixture of 1- and 2-alkyl derivatives.[12] Aromatic aldehydes (ArCHO) in the presence of ethanol gives benzotriazole-based N,O-acetals:

ArCHO + BtH + EtOH → ArCH(OEt)(Bt) + H2O

These acetals are susceptible to deprotonation, giving access to acylsilanes[13] and acylboranes.

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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.[14]

Applications

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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.[citation needed]

Corrosion inhibition

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Benzotriazole is an corrosion inhibitor for copper. It is known that a passive layer, consisting of a complex between copper and benzotriazole, is formed when copper is immersed in a solution containing benzotriazole. The passive layer is insoluble in aqueous and many organic solutions. There is a positive correlation between the thickness of the passive layer and the efficiency of preventing corrosion.[15] BTA is used in heritage conservation, notably for the treatment of bronze disease.

Environmental relevance

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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.[16] It is of low toxicity and a low health hazard to humans although exhibiting some antiestrogenic properties.[17] Benzotriazole (and tolyltriazole) is a common "polar organic persistent pollutant", often detected at >0.1 μg/L.[18] One source of this pollution is their use as anti-icing/deicing agents in airports.[19]

Benzotriazole derivatives

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Many modifications of benzotriazole have been reported.[12][20][21][22] 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.[citation needed]

References

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Benzotriazole (BTA) is a pure compound. Benzotriazole has relatively good water solubility. Benzotriazole is used as the solid dissolved in solvents or in water-based systems as the sodium or potassium salt solution. Benzotriazole has always been of high quality with only slight odor and color. Benzotriazole is the triazole with the highest vapor pressure and starts to sublime at higher temperatures which makes it suitable for vapor applications.  Benzotriazole is available in a variety of forms. The basic raw material benzene or the derived ortho-phenylene diamine (OPD) fluctuates with the price of oil.  Benzotriazole has a bp of 350 deg. C (204 deg C at 15 mm Hg) and a sublimation point of 200 deg C. The pKa Dissociation Constant is 8.37 and the pH in water is 5.5-6.0 with a solubility in water of 1.98 g/l @ 25 deg C.

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