Benzimidazole

Benzimidazole

Skeletal formula with numbering convention
Ball-and-stick model Space-filling model
Names
IUPAC name 1H-benzimidazole
Identifiers
CAS Number	51-17-2 Y
ChEBI	CHEBI:41275 Y
ChEMBL	ChEMBL306226 Y
ChemSpider	5593 Y
Jmol 3D model	Interactive image Interactive image
KEGG	C02009 Y
PubChem	5798
UNII	E24GX49LD8 Y
InChI InChI=1S/C7H6N2/c1-2-4-7-6(3-1)8-5-9-7/h1-5H,(H,8,9) Y Key: HYZJCKYKOHLVJF-UHFFFAOYSA-N Y InChI=1/C7H6N2/c1-2-4-7-6(3-1)8-5-9-7/h1-5H,(H,8,9) Key: HYZJCKYKOHLVJF-UHFFFAOYAX
SMILES n2c1ccccc1nc2 c1ccc2c(c1)[nH]cn2
Properties
Chemical formula	C7H6N2
Molar mass	118.14 g·mol−1
Melting point	170 to 172 °C (338 to 342 °F; 443 to 445 K)
Acidity (pKa)	12.8 (for benzimidazole) and 5.6 (for the conjugate acid)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

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.

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.

Preparation

Benzimidazole is commercially available. The usual synthesis involves condensation of o-phenylenediamine with formic acid, 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.

Applications

Many anthelmintic drugs (albendazole, mebendazole, triclabendazole etc.) belong to the benzimidazole class of compounds.

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
• Benzimidazole fungicides