1081. Benzimidazole

Nomenclature

CAS number: 51-17-2
Benziminazole; 1,3-benzodiazole; azindole; benzoglyoxaline; N,N′-methenyl-o-phenylenediamine.
C7H6N2; mol wt 118.14.
C 71.17%, H 5.12%, N 23.71%.

Description and references

Prepd by the reaction of o-phenylenediamine with formic acid: Wundt, Ber. 11, 826 (1878); Wagner, Millett, Org. Synth. coll. vol. II, 65 (1943). Reviews: J. B. Wright, Chem. Rev. 48, 397-541 (1951); K. Hofmann, Imidazole and Its Derivatives (Interscience, New York, 1953) p 247 sqq.

Chemical structure

Properties

Tabular crystals. Orthorhombic and monoclinic modifications. mp 170.5°. bp760 >360°. Weak base. pKa = 5.48 at 25°. Absorption spectrum: Steck et al., J. Am. Chem. Soc. 70, 3406 (1948). Dipole moment: 3.93 (dioxane). Sparingly sol in cold water, more sol in hot water. Freely sol in alcohol, sparingly sol in ether. Practically insol in benzene, petr ether. One gram dissolves in 2 g of boiling xylene. Sol in aq solns of acids and strong alkalies. High degree of chemical stability.