View source for Benzimidazole

{{chembox
| verifiedrevid = 321986265
| ImageFile = Benzimidazole chemical structure.png 
| ImageSize = 
| IUPACName = 1''H''-benzimidazole
| OtherNames = 
| Section1 = {{Chembox Identifiers
| InChIKey = HYZJCKYKOHLVJF-UHFFFAOYAX
| CASNo_Ref = {{cascite}}
| CASNo = 51-17-2 
| PubChem = 5798
| ChemSpiderID=5593
| SMILES = n2c1ccccc1nc2
| InChI = 1/C7H6N2/c1-2-4-7-6(3-1)8-5-9-7/h1-5H,(H,8,9)}}
| Section2 = {{Chembox Properties
| C=7|H=6|N=2
| Appearance = 
| Density = 
| MeltingPt = 170–172 °C
| BoilingPt = 
| Solubility = }}
| Section3 = {{Chembox Hazards
| ExternalMSDS = [http://msds.chem.ox.ac.uk/BE/benzimidazole.html External MSDS]
| EUClass = Harmful ('''Xn''')
| RPhrases = {{R20}} {{R21}} {{R22}} {{R36}} {{R37}} {{R38}}
| SPhrases = {{S26}} {{S36}}
| FlashPt = 
| Autoignition = }}
}}
'''Benzimidazole''' is a [[heterocyclic]] [[aromatic]] [[organic compound]].  This bicyclic compound consists of the fusion of [[benzene]] and [[imidazole]].  The most prominent benzimidazole compound in nature is ''N''-ribosyl-dimethylbenzimidazole, which serves as an axial ligand for [[cobalt]] in [[Cyanocobalamin|vitamin B<sub>12</sub>]].<ref>{{cite journal
| author = H. A. Barker, R. D. Smyth, H. Weissbach, J. I. Toohey, J. N. Ladd, and B. E. Volcani
| title = Isolation and Properties of Crystalline Cobamide Coenzymes Containing Benzimidazole or 5,6-Dimethylbenzimidazole
| journal = [[Journal of Biological Chemistry]]
| date =  February 1, 1960 | volume = 235
| issue = 2
| pages = 480–488
| url = http://www.jbc.org/cgi/reprint/235/2/480
| pmid = 13796809
}}
</ref>	  

Benzimidazole, in an extension of the well-elaborated [[imidazole]] system, has been used as carbon skeletons for [[N-heterocyclic carbene]]s. The NHCs are usually used as [[ligand]]s for [[transition metal complex]]es. They are often prepared by deprotonating an N,N'-disubstituted benzimidazolium salt at the 2-position with a base.<ref>{{cite journal | author = R. Jackstell, A. Frisch, M. Beller, D. Rottger, M. Malaun and B. Bildstein | title = Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium(0)carbene complexes | year = 2002 | journal = [[Journal of Molecular Catalysis A: Chemical]] | volume = 185 | issue = 1-2 | pages = 105–112 | doi = 10.1016/S1381-1169(02)00068-7}}</ref><ref>{{cite journal | author = H. V. Huynh, J. H. H. Ho, T. C. Neo and L. L. Koh | title = Solvent-controlled selective synthesis of a trans-configured benzimidazoline-2-ylidene palladium(II) complex and investigations of its Heck-type catalytic activity | year = 2005 | journal = [[Journal of Organometallic Chemistry]] | volume = 690 | issue = 16 | pages = 3854–3860 | doi = 10.1016/j.jorganchem.2005.04.053}}</ref>

==Preparation==
Benzimidazole is commercially available. The usual synthesis involves condensation of [[o-phenylenediamine]] with [[formic acid]],<ref name = wagner>{{OrgSynth | title = Benzimidazole | prep = cv2p0065 | collvol = 2 | collvolpages = 65 | year = 1943 | author = E. C. Wagner and W. H. Millett}}</ref> or the equivalent [[orthoformic acid|trimethyl orthoformate]]:
:C<sub>6</sub>H<sub>4</sub>(NH<sub>2</sub>)<sub>2</sub>  +  HC(OCH<sub>3</sub>)<sub>3</sub>  &rarr;  C<sub>6</sub>H<sub>4</sub>N(NH)CH  +  3 [[methanol|CH<sub>3</sub>OH]]

By altering the carboxylic acid used, this method is generally able to afford 2-substituted benzimidazoles.<ref name = wagner/>
Benzimidazole also has fungicidal properties. It acts by binding to the fungal microtubules and stopping hyphal growth. It also binds to the spindle microtubules and blocks nuclear division.

== See also ==
* [[Benzimidazoline]]
* [[Albendazole]], a common use [[anthelmintic]].
* [[Indole]], an analog with CH in place of [[nitrogen]] in position 3.
* [[Purine]], an analog with two additional nitrogen [[atom]]s in the six-membered ring.
* [[Simple aromatic ring]]s
* [[Triclabendazole]], most common drug against [[liver fluke]]s
* [[polybenzimidazole]], a high performance fiber
* [http://www.adichemadi.com/organic/namedreactions/phillips/phillipscondensation1.html Preparation of Benzimidazole by Phillips condensation at AdiChemAdi]

==References==
{{Reflist}}

==Further reading==
*{{cite book |author=Grimmett, M. R. |title=Imidazole and benzimidazole synthesis |publisher=Academic Press |location=Boston |year=1997 |pages= |isbn=0-12-303190-7 |oclc= |doi= |accessdate=}}

{{Anthelmintics}}
{{Excavata antiparasitics}}
{{Antifungals}}

[[Category:Benzimidazoles|*]]
[[Category:Aromatic bases]]

[[ar:بنزيميدازول]]
[[cs:Benzimidazoly]]
[[de:Benzimidazol]]
[[es:Benzimidazol]]
[[ja:ベンゾイミダゾール]]
[[pl:Benzimidazol]]
[[pt:Benzimidazol]]
[[ru:Бензимидазол]]
[[th:เบนซิมิดาโซล]]
[[zh:苯并咪唑]]
[[Category:2Fix]]