Abstract
The deuterium-isotope effects on the ionization constants of β-naphthol (2-naphthol) and boric acid, Δlog 10 K=[log 10 K D2O−log 10 K H2O], have been determined from measurements in light and heavy water at temperatures from 225 °C≤t≤300 °C and pressures near steam saturation. β-Naphthol is a thermally-stable colorimetric pH indicator, whose ionization constant lies close to that of H2PO −4 (aq), the only acid for which Δlog 10 K is accurately known at elevated temperatures. A newly designed platinum flow cell was used to measure UV-visible spectra of β-naphthol in acid, base, and buffer solutions of H2PO −4 /HPO 2−4 and D2PO −4 /DPO 2−4 , from which the degree of ionization at known values of pH and pD was determined. Values of the ionization constants of β-naphthol in light and heavy water were calculated from these results, and used to derive a model for \(\log_{10}K_{\mathrm{H}_{2}\mathrm{O}}\) and \(\log_{10}K_{\mathrm{D}_{2}\mathrm{O}}\) over the experimental temperature range with an estimated precision of ±0.02 in log 10 K. The new values of K H2O and K D2O allowed us to use β-naphthol as a colorimetric indicator, to measure the equilibrium pH and pD of the buffer solutions B(OH)3/B(OH) −4 and B(OD)3/B(OD) −4 up to 300 °C, from which the ionization constants of boric acid were calculated. The magnitude of the deuterium isotope effect for H2PO −4 (aq) is known to fall from Δlog 10 K=−0.62 to Δlog 10 K=−0.47, on the “aquamolal” concentration scale, as the temperature rises above 125 °C, but then remains almost constant. Although the temperature range is more limited, the new results for β-naphthol and boric acid appear to show a similar trend.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Bates, R.: Medium effects and pH in non-aqueous solvents. In: Coetzee, J.F., Ritchie, C.D. (eds.) Solute-Solvent Interactions. Marcel Dekker, New York (1969), Chap. 4
Laughton, P.M., Robertson, R.E.: Solvent isotope effects for equilibria and reactions. In: Coetzee, J.F., Ritchie, C.D. (eds.) Solute-Solvent Interactions. Marcel Dekker, New York (1969), Chap. 7
Arnett, E.M., McKelvey, D.R.: Solvent isotope effect on thermodynamics of non-reacting solutes. In: Coetzee, J.F., Ritchie, C.D. (eds.) Solute-Solvent Interactions. Marcel Dekker, New York (1969), Chap. 6
Jancso, G., Van Hook, W.A.: Condensed phase isotope effects (especially vapor pressure isotope effects). Chem. Rev. 74, 689–750 (1974). doi:10.1021/cr60292a004
Shoesmith, D.W., Lee, W.: The ionization constant of heavy water (D2O) in the temperature range 298 to 523 K. Can. J. Chem. 54, 3553–3558 (1976). doi:10.1139/v76-511
Mesmer, R.E., Herting, D.L.: Thermodynamics of ionization of D2O and D2PO −4 . J. Solution Chem. 7, 901–913 (1978). doi:10.1007/BF00645300
Xiang, T., Johnston, K.P.: Acid-base behavior of organic compounds in supercritical water. J. Phys. Chem. 98, 7915–7922 (1994). doi:10.1021/j100083a027
Clarke, R.G.F., Collins, C.M., Roberts, J.C., Trevani, L.N., Bartholomew, R.J., Tremaine, P.R.: Ionization constants of aqueous amino acids at temperatures up to 250 °C using hydrothermal pH indicators and UV-visible spectroscopy: glycine, α-alanine and proline. Geochim. Cosmochim. Acta 69, 3029–3043 (2005). doi:10.1016/j.gca.2004.11.028
Bulemela, E., Trevani, L.N., Tremaine, P.R.: Ionization constants of aqueous glycolic acid at temperatures up to 250 °C using hydrothermal pH indicators and UV-visible spectroscopy. J. Solution Chem. 34, 769–788 (2005). doi:10.1007/s10953-005-5113-x
Ehlerova, J., Trevani, L.N., Sedlbauer, J., Tremaine, P.R.: Spectrophotometric determination of the ionization constants of aqueous nitrophenols at temperatures up to 225 °C. J. Solution Chem. 37, 854–857 (2008). doi:10.1007/s10953-008-9279-x
Wehry, E.L., Rogers, L.B.: Deuterium isotope effects on the protolytic dissociation of organic acids in electronically excited states. J. Am. Chem. Soc. 88, 351–354 (1966). doi:10.1021/ja00954a031
Trevani, L.N., Roberts, J.C., Tremaine, P.R.: Copper(II)-ammonia complexation equilibria in aqueous solutions from 30 to 250 °C by visible spectroscopy. J. Solution Chem. 30, 585–622 (2001). doi:10.1023/A:1010453412802
Bulemela, E.: Hydration and functional group effects of organic solutes in water at high temperatures and pressures. PhD thesis, University of Guelph (2006)
Mendham, J., Denney, R.C., Barnes, J.D., Thomas, M.: Vogel’s Textbook of Quantitative Chemical Analysis, 6th edn. Prentice Hall, Harlow (2000)
Trevani, L.N., Balodis, E., Tremaine, P.R.: Apparent and standard partial molar volumes of NaCl, NaOH, and HCl in water and heavy water at 523 K and 573 K at p=14 MPa. J. Phys. Chem. B 111, 2015–2024 (2007). doi:10.1021/jp063824x
Pitzer, K.S.: Thermodynamics. McGraw Hill, New York (1995)
Uematsu, M., Franck, E.U.: Static dielectric constant of water and steam. J. Phys. Chem. Ref. Data 9, 1291–1306 (1980)
Mesmer, R.E., Baes, C.F. Jr.: Phosphoric acid dissociation equilibria in aqueous solutions to 300 °C. J. Solution Chem. 4, 307–322 (1974) doi:10.1007/BF00648228
Mesmer, R.E., Baes, C.F. Jr., Sweeton, F.H.: Acidity measurements at elevated temperatures, VI: boric acid equilibria. Inorg. Chem. 11, 537–543 (1972) doi:10.1021/ic50109a023
Palmer, D.A., Bénézeth, P., Wesolowski, D.J.: Boric acid hydrolysis: a new look at the available data. PowerPlant Chem. 2, 261–264 (2000)
Albert, A., Serjeant, E.P.: Ionization Constants of Acids and Bases. Methuen, London (1969)
Edwards, J.O., Ibne-Rasa, K.M., Choi, E.I., Rice, C.L.: Kinetic deuterium isotope effect in the nitrosation of aniline. The deuterium isotope effect on three equilibrium constants. J. Phys. Chem. 66, 1212–1213 (1962) doi:10.1021/j100812a522
Gold, V., Lowe, B.M.: Measurement of solvent isotope effects with the glass electrode, part II: the dissociation constant of acetic acid and boric acid in D2O and D2O-H2O mixtures, J. Chem. Soc. A 1923–1932 (1968). doi:10.1039/j19680001923
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bulemela, E., Tremaine, P.R. D2O Isotope Effects on the Ionization of β-Naphthol and Boric Acid at Temperatures from 225 to 300 °C using UV-Visible Spectroscopy. J Solution Chem 38, 805–826 (2009). https://doi.org/10.1007/s10953-009-9411-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10953-009-9411-6