Benzimidazole
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| IUPAC name
1H-benzimidazole
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| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.000.075 |
| KEGG | |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C7H6N2 | |
| Molar mass | 118.139 g·mol−1 |
| Melting point | 170–172 °C |
| Acidity (pKa) | 12.8 (for benzimidazole) and 5.6 (for the conjugate acid) [1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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 vitamin B12.[2]
Benzimidazole, in an extension of the well-elaborated imidazole system, has been used as carbon skeletons for N-heterocyclic carbenes. The NHCs are usually used as ligands for transition metal complexes. They are often prepared by deprotonating an N,N'-disubstituted benzimidazolium salt at the 2-position with a base.[3][4]
Preparation
Benzimidazole is commercially available. The usual synthesis involves condensation of o-phenylenediamine with formic acid,[5] or the equivalent trimethyl orthoformate:
- C6H4(NH2)2 + HC(OCH3)3 → C6H4N(NH)CH + 3 CH3OH
By altering the carboxylic acid used, this method is generally able to afford 2-substituted benzimidazoles.[5] 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
- Polybenzimidazole, a high performance fiber
- Indole, an analog with CH in place of nitrogen in position 3.
- Purine, an analog with two additional nitrogen atoms in the six-membered ring.
- Simple aromatic rings
References
- ^ Walba, H. & Isensee, R. W. Acidity constants of some arylimidazoles and their cations. J. Org. Chem. 26, 2789-2791 (1961).
- ^ H. A. Barker, R. D. Smyth, H. Weissbach, J. I. Toohey, J. N. Ladd, and B. E. Volcani (February 1, 1960). "Isolation and Properties of Crystalline Cobamide Coenzymes Containing Benzimidazole or 5,6-Dimethylbenzimidazole". Journal of Biological Chemistry. 235 (2): 480–488. PMID 13796809.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ R. Jackstell, A. Frisch, M. Beller, D. Rottger, M. Malaun and B. Bildstein (2002). "Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium(0)carbene complexes". Journal of Molecular Catalysis A: Chemical. 185 (1–2): 105–112. doi:10.1016/S1381-1169(02)00068-7.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ H. V. Huynh, J. H. H. Ho, T. C. Neo and L. L. Koh (2005). "Solvent-controlled selective synthesis of a trans-configured benzimidazoline-2-ylidene palladium(II) complex and investigations of its Heck-type catalytic activity". Journal of Organometallic Chemistry. 690 (16): 3854–3860. doi:10.1016/j.jorganchem.2005.04.053.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b E. C. Wagner and W. H. Millett (1943). "Benzimidazole". Organic Syntheses; Collected Volumes, vol. 2, p. 65..
Further reading
- Grimmett, M. R. (1997). Imidazole and benzimidazole synthesis. Boston: Academic Press. ISBN 0-12-303190-7.