有機溶媒・水系中におけるアセチルサリチル酸の加水分解に関する速度論的研究(第2報)

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タイトル別名
  • Kinetic Studies on the Hydrolysis of Acetylsalicylic Acid in Binary Systems of Water and Organic Solvents. II
  • 有機溶媒・水系中におけるアセチルサリチル酸の加水分解に関する速度論的研究-2-
  • ユウキ ヨウバイ スイケイ チュウ ニ オケル アセチル サリチルサン ノ カスイ ブンカイ ニ カンスル ソクドロンテキ ケンキュウ 2

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説明

This kinetic study dealt with the hydrolysis of acetylsalicylic acid (ASP) in the aqueous solution of dimethyl sulfoxide (DMSO) at different solvent concentrations, pH, and temperature. The hydrolysis rate at pH 7 and 8 increased with increasing DMSO concentration, but that at pH6 especially decreased at higher concentration than 8 molal DMSO. The reaction rate in aqueous solution at the most stable pH, that is 2.3, also decreased by the addition of DMSO. The pH independent region of the hydrolysis rate observed in aqueous solution from pH 5 to 7 shifted to a higher pH from 9 to 13 by the addition of DMSO. Since the ionic dissociation of ASP observed by ultraviolet absorption was strongly suppressed by DMSO, the decrease of the rate in the aqueous DMSO solution at pH 6 could be mainly due to the decrease of the ASP anion which is a more reactive species. The first-order rate constant of ASP anion estimated by the observed pKa was almost constant below the molar ratio of [DMSO]/[H2O]=0.3, but it increased at a higher concentration of DMSO. The relationship between the reaction rate constant and macroscopic dielectric constant of the solution could not be expressed by Awis' expression of anion-dipole reaction. The relationship between the activation enthalpy and entropy in various aqueous solution, i.e., EtOH, propylene glycol, dimethylacetamide, and DMSO was expressed by a straight line of Leffler's isokinetic equation.

収録刊行物

  • 薬学雑誌

    薬学雑誌 93 (11), 1427-1432, 1973

    公益社団法人 日本薬学会

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