Electronic spectra of benzimidazolecarboxylic acids: effect of solvents and acid concentrations

✍ Scribed by Hemant K. Sinha; Sneh K. Dogra

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 592 KB
• Volume: 45
• Category: Article
• ISSN: 1386-1425
• DOI: 10.1016/0584-8539(89)80242-9

✦ Synopsis

Effect of solvents and acid concentration on the absorption and fluorescence spectra of benzimidazole-2-acetic acid (BIAA), benzimidazole-2-methylacetate (BIAE) and benzimidazole-2-propionic acid have been investigated. The results have indicated that the presence of the methylene group reduces the interaction of BI and -COOH groups. For example, the spectral characteristics of BIAE and BIPA are similar to 2-methylbenzimidazole (MBI). The long wavelength absorption band in BIAA is assigned to the presence of an intramolecular hydrogen-bonded structure and hydrogen bonding is stronger in the S, state than in the S, state. In aqueous medium, depending upon the pH of the solution, BIAA and BIPA either exist as zwitterion or monoanion. The zwitterion and monoanion of BIAA have a ring structure, whereas those of BIPA have an open structure.