Abstract
Potentiometric titration has been used to study the protolytic equilibria on the surface of carboxyl-containing silica (CS) prepared by the reaction of silica (Silokhrom S-80, Ssp = 80 m2/g) with Cl3SiCH2CH2COOCH3, followed by hydrolysis with 30% sulfuric acid. The titration curve of the vacuum-dried sample is irreversible. The titration curve of its Na+ form with hydrochloric acid proceeds lower than the titration curve of its H+ form and coincides with the titration curve of the air-dried sample (the last curve is reversible). The titration curve of CS coincides with the titration curve of butyric acid at pH < 6. At pH > 6 the titration curve of CS passes below the titration curve of butyric acid; this is due to the participation of silanol groups on the silica surface in the protolytic equilibria. The pKa of the grafted CS groups is equal to 4.80 which is close to the pKa value of butyric acid (4.78). A method has been proposed for the determination of the amount of weak acid groups grafted to the silica. It has been shown that in the titration of CS the equilibrium is established much faster than in the case of the unmodified silica.
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Literature cited
I. E. Neimark, Synthetic Mineral Adsorbents and Catalyst Supports [in Russian], Naukova Dumka, Kiev (1982).
G. V. Lisichkin, G. V. Kudryavtsev, and P. N. Nesterenko, “Chemically modified silicas and their use in inorganic analysis,” Zh. Anal. Khim., 38, No. 9, 1684–1705 (1983).
K. K. Unger, Porous Silica, Its Properties and Use as Support in Column Liquid Chromatography, Elsevier, Amsterdam (1979).
G. V. Lisichkin and A. Ya. Yuffa, Heterogeneous Metal-Complex Catalysts [in Russian], Khimiya, Moscow (1981).
G. V. Kudryavtsev and G. V. Lisichkin, “Comparison of the properties of ligands grafted to the silica surface and their complexes with homogeneous analogs,” Adsorbtsiya i Adsorbenty, No. 12, 33–39 (1984).
G. V. Kudryavtsev and G. V. Lisichkin, “Acid-base properties of silica modified chemically with γ-aminopropyltriethoxysilane,” Zh. Fiz. Khim., 55, No. 5, 1352–1354 (1981).
G. V. Kudryavtsev, G. V. Lisichkin, and V. M. Ivanov, “Acid-base properties of silica with ethylenediamine grafted chemically to its surface,” Zh. Vses. Khim. Ob-va im. D. I. Mendeleeva, 26, NO. 3, 345–347 (1981).
V. A. Tertykh, A. A. Agzamkhodzhaev, A. A. Chuiko, and L. T. Zhuravlev, “Synthesis and investigation of the surface chemistry of aminoorganosilicas,” Izv. Akad. Nauk SSSR, Ser. Khim., No. 8, 1739–1743 (1968).
D. E. Leyden, D. S. Kendall, and T. G. Waddell, “Carbon-13 cross-polarization with magic angle spinning nuclear magnetic resonance spectroscopy of organosilanes bonded to silica surfaces,” Anal. Chim. Acta, 126, No. 2, 207–212 (1981).
S. Shinoda and Y. Saito, “Hydrogen bonding in silica-bonded amino groups as probed by carbon-13 spin-lattice relaxation times,” J. Colloid Interface sci., 89, No. 1, 293–295 (1982).
P. R. Moses, L. M. Wier, J. C. Lennox, et al., “X-ray photoelectron spectroscopy of alkylaminosilanes bound to metal oxide electrides,” Anal. Chem., 50, No. 4, 576–585 (1978).
R. A. Pike and W. T. Black, “Chlorosilanes and derivatives of acrylates,” British Patent No. 882101.
N. K. Shoniya, S. M. Staroverov, Yu. S. Nikitin, and G. V. Lisichkin, “Adsorption properties of silicas modified chemically with long-chain organic compounds,” Zh. Fiz. Khim., 58, No. 3, 702–707 (1984).
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Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 2, pp. 243–247, March–April, 1986.
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Mil'chenko, D.V., Kudryavtsev, G.V. & Lisichkin, G.V. Protolytic equilibria on the surface of carboxyl-containing silica. Theor Exp Chem 22, 227–230 (1986). https://doi.org/10.1007/BF00519201
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DOI: https://doi.org/10.1007/BF00519201