Determination of acidity constant values some benzimidazole derivative compounds in non-aqueous media

SUMMARYDetermination of Acidity Constant Values Some Benzimidazole Derivative Compounds in Non-Aqueous MediaTen new benzimidazole derivative compounds were synthesized and investigated by potentiometric method. It was determinated that the benzimidazole derivative were biological active compounds. Because of that, the benzimidazole derivative compounds are very important in many practical application. Because of scarcely low solubility of the compounds in water, non-aqueous media were prefered. The following principles were considered in choosing the non-aqueous solvents used; They should be widely used in the non-aqueous solution media, be from different solvents groups, and have distinct autoprolysis constants. In non-qaueous medium, 2-propanol and tert-butyl alcohol among the amphiprotic type, and acetonitrile and N,N-dimethylformamide among the dipolar aprotic type were taken as solvent. Tetrabuthylamonnium hydroxide (TBAH) in 2-propanol, a titrant widely used in non-aqueous titrations, was used as titrant in all titrations. The potentiometric method used in determining the end-points in titrimetric analyses was utilized for the determination of acidity. The results obtained from the titrations are presented in tables and graphs. Typical sigmoid shaped titration curves are observed in the graphs. The acidity constants of the compounds in the solvents chosen were calculated using the graphs and the data obtained with half-neutralization method. The acidity strength of the compounds was observed to differ from the information obtained. The acidity strength of ten new benzimidazole derivative compounds in different solvents, dielectric constant of the solvents, autoprotolysis constant and leveling-differentiation effects were investigated. pKa values of compounds were in the range of 11.91 - 15.75 for 2-propanol, 12.22 - 16.54 for N,N-dimethylformamide, 12.42 - 16.58 for tert-butyl alcohol, 12.37 - 16.76 for acetonitrile.Keywords: Non-Aqueous Media, pKa Values, Half-Neutralization Method,Potentiometric Titration