View source for Benzotriazole

{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464365248
| ImageFile_Ref = {{chemboximage|correct|??}}
| ImageFile = Benzotriazole - numbered.png
| ImageSize = 160
| ImageAlt = Skeletal formula of benzotriazole
| ImageFile1 = Benzotriazole-3D-spacefill.png
| ImageSize1 = 160
| ImageAlt1 = Space-filling model of the benzotriazole molecule
| PIN = 1''H''-1,2,3-Benzotriazole
| OtherNames = 1''H''-Benzotriazole; 1,2,3-Benzotriazole; BTA; BtaH
|Section1={{Chembox Identifiers
| Abbreviations = 
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 6950
| InChIKey = QRUDEWIWKLJBPS-UHFFFAOYAH
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 84963
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C6H5N3/c1-2-4-6-5(3-1)7-9-8-6/h1-4H,(H,7,8,9)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = QRUDEWIWKLJBPS-UHFFFAOYSA-N
| CASNo = 95-14-7
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 7220
| SMILES = n1c2ccccc2[nH]n1
| InChI = 1/C6H5N3/c1-2-4-6-5(3-1)7-9-8-6/h1-4H,(H,7,8,9)
| EC_number = 202-394-1
| RTECS = DM1225000
| UNII = 86110UXM5Y
| MeSHName =
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 75331
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = 
}}
|Section2={{Chembox Properties
| C=6 | H=5 | N=3
| Appearance = White solid
| Density = 1.36 g/mL<ref name="Merck">{{cite web|url=https://www.emdmillipore.com/US/en/product/1H-Benzotriazole%2CMDA_CHEM-822315 |title=1H-Benzotriazole (CAS 95-14-7) |archive-url=https://web.archive.org/web/20201024211944/https://www.emdmillipore.com/US/en/product/1H-Benzotriazole,MDA_CHEM-822315 |archive-date=2020-10-24}}''</ref>
| MeltingPtC = 100
| MeltingPt_ref =<ref name="SRC">[http://esc.syrres.com/interkow/webprop.exe?CAS=95-14-7 1H-Benzotriazole] {{webarchive |url=https://web.archive.org/web/20070927230759/http://esc.syrres.com/interkow/webprop.exe?CAS=95-14-7 |date=September 27, 2007}}, SRC PhysProp Database</ref>
| BoilingPtC = 350
| BoilingPt_ref =<ref name="SRC"/>
| Solubility = 20 g/L<ref name="SRC"/>
| SolubleOther = 
| Solvent = 
| pKa = 8.2<ref name="Benzotriazole: A novel synthetic auxiliary">{{cite journal |last=Katritzky |first=A. R. |author2=Rachwal S. |author3=Hitchings G. J. |title=Benzotriazole: A novel synthetic auxiliary |journal=Tetrahedron |date=14 January 1991 |issue=16–17 |pages=2683–2732 |doi=10.1016/S0040-4020(01)87080-0 |volume=47}}</ref><ref name="Adventures with Benzotriazole">{{cite web |last=Katritzky |first=A. R. |title=Adventures with Benzotriazole |url=http://www.ark.chem.ufl.edu/Lectures/Benzotriazole_2002.pdf |work=Lecture presented at various locations in 2002 |publisher=Florida Center for Heterocyclic Compounds |accessdate=23 November 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20120426001244/http://www.ark.chem.ufl.edu/Lectures/Benzotriazole_2002.pdf |archivedate=26 April 2012}}</ref>
| pKb = > 14<ref name="Adventures with Benzotriazole"/>
}}
|Section3={{Chembox Structure
| CrystalStruct = 
| Coordination = 
| MolShape = }}
|Section4={{Chembox Thermochemistry
| DeltaHf = 
| DeltaHc = 
| Entropy = 
| HeatCapacity = }}
|Section5={{Chembox Pharmacology
| AdminRoutes =
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| HalfLife = 
| ProteinBound =
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| Legal_status =
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| Pregnancy_category = 
| Pregnancy_AU = 
| Pregnancy_US = }}
|Section6={{Chembox Explosive
| ShockSens = 
| FrictionSens = 
| DetonationV = 
| REFactor = }}
|Section7={{Chembox Hazards
| ExternalSDS = 
| GHSPictograms = {{GHS exclamation mark}}{{GHS environment}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|319|332|411|412}}
| PPhrases = {{P-phrases|261|264|270|271|273|280|301+312|304+312|304+340|305+351+338|312|330|337+313|391|501}}
| NFPA-H = 
| NFPA-F = 
| NFPA-R = 
| NFPA-S =
| FlashPt = 
| AutoignitionPt = 
| ExploLimits = 
| PEL = }}
|Section8={{Chembox Related
| OtherAnions = 
| OtherCations = 
| OtherFunction = 
| OtherFunction_label = 
| OtherCompounds = [[Benzimidazole]], [[Tolyltriazole]]}}
}}

'''Benzotriazole''' (BTA) is a [[heterocyclic compound]] with the chemical formula C<sub>6</sub>H<sub>5</sub>N<sub>3</sub>. Its five-membered ring contains three consecutive nitrogen atoms. This bicyclic compound may be viewed as fused rings of the aromatic compounds [[benzene]] and [[triazole]]. This white-to-light tan solid has a variety of uses, for instance, as a [[corrosion inhibitor]] for copper.<ref>{{Cite web |title=1,2,3-BENZOTRIAZOLE {{!}} CAMEO Chemicals {{!}} NOAA |url=https://cameochemicals.noaa.gov/chemical/19869 |access-date=2023-01-17 |website=cameochemicals.noaa.gov}}</ref>

==Structure==
Benzotriazole features two fused rings. Its five-membered ring can in principle exist as [[tautomer]]s A and B:<ref name="Benzotriazole: A Review for Conservators">{{cite journal |last=Sease |first=Catherine |title=Benzotriazole: A Review for Conservators |journal=Studies in Conservation |date=May 1978 |volume=23 |series=2 |pages=76–85 |jstor=1505798 |doi=10.2307/1505798 |issue=2}}</ref><br>
:[[File:Benzotriazole tautomers and their derivatives (cropped).png|380px|Benzotriazole tautomers]]
Various structural analyses with UV, IR and <sup>1</sup>H-NMR spectra indicate that tautomer A is dominant.

==Synthesis and reactions==
Synthesis of benzotriazole involves the reaction of [[o-Phenylenediamine|''o''-phenylenediamine]], [[sodium nitrite]], and [[acetic acid]]. The conversion proceeds via [[diazotization]] of one of the amine groups:<ref name=Ullmann>Robert A. Smiley "Phenylene- and Toluenediamines" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2002, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a19_405}}</ref><ref>{{cite journal |doi=10.15227/orgsyn.020.0016 |title=1,2,3-Benzotriazole |journal=Organic Syntheses |date=1940 |volume=20 |page=16|first1=R. E.|last1=Damschroder|first2=W. D.|last2=Peterson }}</ref>
:[[File:Benzotriazole_synthesis_01.svg|600px|Synthesis of benzotriazole]]

The synthesis can be improved when the reaction is carried out at low temperatures (5–10&nbsp;°C) and briefly irradiated in an [[ultrasonic bath]].<ref>{{cite journal |last1=Pereira |first1=Claudio M. P. |last2=Stefani |first2=Helio A. |last3=Guzen |first3=Karla P. |last4=Orfao |first4=Aline T. G. |date=2007-07-31 |title=Improved Synthesis of Benzotriazoles and 1-Acylbenzotriazoles by Ultrasound Irradiation. |url=https://onlinelibrary.wiley.com/doi/10.1002/chin.200731104 |journal=ChemInform |volume=38 |issue=31 |doi=10.1002/chin.200731104 |issn=0931-7597}}</ref> Typical batch purity is 98.5% or greater.<ref>{{cite web |url=http://chemceed.com/products/benzotriazole/ |title=Benzotriazole - Chemical Supplier Distributor Chemceed}}</ref>

===Reactions===
BTA is a weak acid with a pK<sub>a</sub>&nbsp;=&nbsp;8.2<ref name="Benzotriazole: A novel synthetic auxiliary"/><ref name="Adventures with Benzotriazole"/> 

It is a very weak Brønsted base with pK<sub>a</sub>&nbsp;<&nbsp;0.<ref name="Adventures with Benzotriazole"/> 

Not only can it act either as an acid or base, it can also bind to other species, utilizing the lone pair electrons. Applying this property, the BTA can form a stable coordination compound on a copper surface and behave as a corrosion inhibitor.<ref name="Benzotriazole: A Review for Conservators"/>

Benzotriazole (BtH) reacts with aromatic aldehydes (ArCHO) in the presence of ethanol to give benzotriazole-based N,O-acetals:
:{{chem2|ArCHO  +  BtH  +  EtOH  ->  ArCH(OEt)(Bt)  +  H2O}}
These acetals are susceptible to deprotonation, giving access to [[acylsilane]]s<ref>{{cite journal |doi=10.1021/om950712b |title=Novel and Convenient Synthesis of Aroyl-, Heteroaroyl-, Alkenoyl-, and Alkynoylsilanes |date=1996 |last1=Katritzky |first1=Alan R. |last2=Wang |first2=Zuoquan |last3=Lang |first3=Hengyuan |journal=Organometallics |volume=15 |issue=2 |pages=486–490 }}</ref> and [[acylborane]]s.

''N''-amination of BtH with [[hydroxylamine-O-sulfonic acid|hydroxylamine-''O''-sulfonic acid]] gives 1-aminobenzotriazole.  Oxidation of this amine with [[lead(IV) acetate]] affords [[benzyne]], which rapidly [[dimer (chemistry)|dimerises]] to [[biphenylene]].<ref>{{cite journal |first1=C.D. |last1=Campbell |first2=C.W. |last2=Rees |authorlink2=Charles Rees |journal=[[J. Chem. Soc. C]] |title=Reactive intermediates. Part I. Synthesis and oxidation of 1- and 2-aminobenzotriazole |volume=1969 |issue=5 |pages=742–747 |year=1969 |doi=10.1039/J39690000742}}</ref>
:[[File:Dehydrobenzol aus Aminobenztriazol.svg|400px|Synthesis of Benzyne and Biphenylene from 1''H''-Benzotriazole]]

==Applications==
Benzotriazole has been known for its great versatility. It has already been used as a restrainer (or anti-fogging agent) in [[photographic emulsion]]s 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. Also, its derivatives and their effectiveness as drug precursors have been drawing attention. Besides all the applications mentioned above, the BTA can be used as antifreezes, heating and cooling systems, [[hydraulic fluid]]s, and vapor-phase inhibitors as well.<ref name="Benzotriazole: A Review for Conservators"/>

===Corrosion inhibition===
Benzotriazole is an effective corrosion inhibitor for copper and its alloys by preventing undesirable surface reactions. 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.<ref name="Inhibition of copper corrosion by 1,2,3-benzotriazole: A review">{{cite journal |last=Finšgar |first=M. |author2=Milošev I. |title=Inhibition of copper corrosion by 1,2,3-benzotriazole: A review |journal=Corrosion Science |date=11 March 2010 |volume=52 |pages=2737–2749 |doi=10.1016/j.corsci.2010.05.002 |issue=9}}</ref>  BTA is used in heritage conservation, notably for the treatment of [[bronze disease]]. The exact structure of the copper-BTA complex is controversial and many proposals have been suggested.{{Citation needed|date=December 2016}}

[[File:PolyCubtri.svg|thumb|left|320 px|Chemical structure of the [[coordination polymer]] from benzotriazolate and copper(I), the active ingredient in the BT-derived corrosion inhibition]]

===Drug precursor===
Benzotriazole [[derivative (chemistry)|derivatives]] have chemical and biological properties that are versatile in the pharmaceutical industry. Benzotriazole derivatives act as agonists for many proteins. For instance, [[vorozole]] and [[alizapride]] have useful inhibitory properties against different proteins. Benzotriazole esters are used as mechanism-based inactivators to treat severe acute respiratory syndrome (SARS) by inhibiting the SARS 3CL protease of the [[SARS-CoV-1]] virus. The methodology is not only limited to heterocyclization but was also successful for polynuclear hydrocarbons of small carbocyclic systems.<ref name="Recent developments in benzotriazole methodology for construction of pharmacologically important heterocyclic skeletons">{{cite journal |last=Kale |first=Raju R. |author2=Virendra Prasad |author3=Prabhu P. Mohapatra |author4= Vinod K. Tiwari |title=Recent developments in benzotriazole methodology for construction of pharmacologically important heterocyclic skeletons |journal=Monatsh Chemistry |date=6 March 2010 |volume=141 |pages=1159–1182 |doi=10.1007/s00706-010-0378-1 |issue=11 |s2cid=93911988|doi-access=free }}</ref>

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==Environmental relevance==
Benzotriazole is fairly water-soluble, not readily degradable and has a limited sorption tendency. Hence, it is only partly removed in [[sewage treatment|wastewater treatment plants]] and a substantial fraction reaches surface water such as rivers and lakes.<ref>{{cite journal |pmid=17180965 |year=2006 |last1=Giger |first1=W |last2=Schaffner |first2=C |last3=Kohler |first3=HP |title=Benzotriazole and tolyltriazole as aquatic contaminants. 1. Input and occurrence in rivers and lakes |volume=40 |issue=23 |pages=7186–92 |journal=Environmental Science & Technology |doi=10.1021/es061565j}}</ref> It is considered to be of low toxicity and a low health hazard to humans although exhibiting some antiestrogenic properties.<ref name="FarréPérez2008">{{cite journal |last1=Farré |first1=Marinel la |last2=Pérez |first2=Sandra |last3=Kantiani |first3=Lina |last4=Barceló |first4=Damià |title=Fate and toxicity of emerging pollutants, their metabolites and transformation products in the aquatic environment |journal=TrAC Trends in Analytical Chemistry |volume=27 |issue=11 |year=2008 |pages=991–1007 |issn=0165-9936 |doi=10.1016/j.trac.2008.09.010}}</ref>

==Related compounds==
[[Tolyltriazole]] is a mixture of isomers or [[congener (chemistry)|congener]]s that differ from benzotriazole by the addition of one methyl group attached somewhere on the benzene ring. Tolyltriazole has similar uses, but has better solubility in some organic solvents.{{Citation needed|date=September 2022}}

==References==
{{Commons category-inline|Benzotriazole}}
{{Reflist|30em}}

{{Authority control}}
[[Category:Benzotriazoles]]
[[Category:Chelating agents]]
[[Category:Conservation and restoration materials]]
[[Category:Corrosion inhibitors]]
[[Category:Photographic chemicals]]