K. Panneerselvam, T. Lu, Ta-Yung Chi
Sep 1, 2000
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Analytical Sciences
Abstract
chemical reactions involving acid-base equilibria. Eventually, most of the commonly employed buffer systems are very good complex-forming agents in the presence of metal ions.1 Both kinetic and thermodynamic studies require non-coordinating buffer systems to be applied in work involving hydrated metal ions so as to avoid complex formation between the buffer and metal ions or a catalytic effect of the buffer on reactions that are subject to acid catalysis.2 Bips et al. (1983)3 have reported on 2,6-dimethyl-pyridine-type compounds as a non-coordinating buffer system in aqueous solution.3 2,6-Dimethyl-pyridine-3sulfonic acid could serve as an alternative to acetate buffer (pKa = 4.8 at 25 ̊C) and as an excellent non-coordinating compound, which would minimize any metal-buffer interaction.3,4 Both ultraviolet and infrared spectra have been reported by Evans and Brown (1962),5 but no crystallographic work has been performed on 2,6-dimethyl-pyridine-3-sulfonic acid. In the present paper, we report on the crystal structure of the title compound (Fig. 1) based on a single-crystal X-ray analysis. 2,6-Dimethyl-pyridine-3-sulfonic acid was prepared by the sulfonation of 2,6-dimethylpyridine, essentially as described by McElvain and Goese6 for the sulfonation of pyridine. The compound was recrystallized from hot water after a prior treatment with charcoal. Colorless crystals were obtained from hot water by slow evaporation. The molecular structure of the title compound appeared as shown in Fig. 2. 2,6-Dimethyl-pyridine-3-sulfonic acid 999 ANALYTICAL SCIENCES SEPTEMBER 2000, VOL. 16 2000 © The Japan Society for Analytical Chemistry