Title: Benzimidazole
CAS Registry Number: 51-17-2
Synonyms: Benziminazole; 1,3-benzodiazole; azindole; benzoglyoxaline;
N,N￠-methenyl-
o-phenylenediamine
Molecular Formula: C7H6N2
Molecular Weight: 118.14
Percent Composition: C 71.17%, H 5.12%, N 23.71%
Literature 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.
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.
Melting point: mp 170.5°
Boiling point: bp760 >360°
pKa: pKa = 5.48 at 25°
