Determination of the Dissociation Constant of Some Substituted Phenols by Potentiometric Method in Acetonitrile-Water Mixtures

Year 2010, Volume: 5 Issue: 1, 60 - 66, 25.06.2010

Güzide Ertokuş Ahmet Aktaş

Abstract

 The dissociation constants of phenol, 2−methylphenol, 3−methylphenol, 4−methylphenol, and 4−ethylphenol have been determined by potentiometric titration in a electrochemical cell with glass electrode at 25 o C in water and in the mixtures of acetonitrile and water where the following volume fractions (before mixing) of acetonitrile were used: 0.10, 0.20, and 0.30. The ionic strength of the solutions was adjusted to be 0.1 mol dm−3 using KCl. The dissociation constants were calculated by using the commercial Hyperquad 2008 program. The obtained results are in good concordance withliterature values.

Keywords

Phenols, acid dissociation constant, potentiometric method

Bazı Substitue Fenollerin Ayrışma Sabitlerinin Asetonitril-Su Karışımlarında Potansiyometrik Metotla Tayini

Abstract

Fenol, 2-metilfenol, 3-metilfenol, 4-metilfenol ve 4-etilfenol’ün ayrışma sabitleri %10-20-30 oranlarında hazırlanan asetonitril –su karışımında 25 o C potansiyometrik olarak elektrokimyasal hücrede elektrot ile tayin edilmiştir.Titrasyon çözeltilerinde iyonik şiddet KCl kullanılarak 0.1 mol dm−3 olarak ayarlanmıştır. Ayrışma sabitleri ticari bir program olan Hyperquad 2008 ile hesaplanmıştır. Elde edilen sonuçlar literatürdeki değerlerle uyumluluk göstermektedir.

Keywords

Fenol, asidik ayrışma sabiti, potansiyometrik yöntem

References

• Pekcan G., Aktaş A.H., 2006. Spectrophotometric determination of pK(a) values for some benzoic acid compounds in acetonitrile-water mixtures. Asian Journal of Chemistry, 18: 2168-2178.
• Ertokuş Pekcan G., Aktaş A.H., 2009. Potentiometric Determination of pK(a) Values of Benzoic Acid and Substituted Benzoic Acid Compounds in Acetonitrile-Water Mixtures. Asian Journal of Chemistry, 21: 3825-3835.
• Wrobel R., Chmurzynski L., 2000. Potentiometric pK(a) determination of standard substances in binary solvent systems. Analytica Chimica Acta, , 405: 303-308.
• Ràfols C., Rosés M., Bosch E., 1997. Dissociation constants of several non-steroidal anti- inflammatory drugs in isopropyl alcohol/water mixtures, Analytica Chimica Acta, 350: 249- 255.
• Ertokuş Pekcan G., Aktaş A.H., 2008. Ionization constants and partition coefficient of some antiinflammatory agents in non-aqueous media. Asian Journal of Chemistry, 20: 3042-3048.
• Aktaş A.H., Şanli N., Pekcan G., 2006. Spectrometric determination of pK(a) values for some phenolic compounds in acetonitrile-water mixture. Acta Chimica Slovenica, 53: 214-218.
• Rondinini S., Mussini P.R. , Mussini T.,1987. Reference value standards and primary standards for pH measurements in organic solvents and water + organic solvent mixtures of moderate to high permittivities, Pure Applied Chemistry, 59: 1549.
• Mussini P.R., Mussini T., Rondinini S., 1997. Reference value standards and primary standards for pH measurements in D2O and aqueous organic solvent mixtures: New accessions and assessments, Pure Applied Chemistry , 69: 1007.
• Gran G., 1952. Determination of the equivalence point in potentiometric titrations-- Part II. Analyst, 77: 661-671.
• Gans P., Sabatini A., Vacca A., 1996. Investigation of equilibria in solution. Determination of equilibrium constants with the HYPERQUAD suite of program. Talanta, 43: 1739-1753.
• Diamond D., Hanratty V.C.A., 1997. Spreadsheet application in chemistry using microsoft excel, Chapter 5, New York, NY:Wiley, pp. 130-145.
• Espinosa S., Bosch E., Rosés M., 2002. Retention of ionizable compounds in high-performance liquid chromatography: IX. Modelling retention in reversed-phase liquid chromatography as a function of pH and solvent composition with acetonitrile–water mobile phases.. Journal of Chromotography, 964: 55-66.
• Hakan Aktaş email: [e-mail]