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1995 (1)
1Author    Kumiko Ohtsu, Kazuhiko Ozutsumi, Makoto Kurihara, Takuji KawashimaRequires cookie*
 Title    Thermodynamics of Complexation of Sodium Ion with 12-Crown-4 and 18-Crown-6 in Pyridine  
 Abstract    The complexation of sodium ion with 1,4,7,10-tetraoxacyclododecane (12-crown-4) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) has been studied by titration calorimetry in pyridine (P Y) containing 0.1 mol dm-3 (C2H5)4NC 104 as a constant ionic medium at 25 °C. The calorimetric titration data were well explained in terms of the formation of the [Na(12-crown-4)]+, [Na(12-crown-4)2]+, and [Na(18-crown-6)]+ complexes, and their formation constants, reaction enthalpies, and entropies were determined. The formation of [Na(18-crown-6)]+ is much pronounced in PY over yV,7V-dimethylformamide (D M F) and water, and the stability order is PY > DMF > water. The enthalpy values for the formation of [Na(18-crown-6)]+ are all negative in PY, DMF, and water, and increase in the order PY < DMF < water. The complexation is the least exothermic in water, though sodium ion is the most weakly solvated in water. This is because 18-crown-6 is much stabilized in water by forming hydrogen bonds with water molecules. Despite the stronger electron pair-donat­ ing ability of PY than DMF, the complexation is more exothermic in PY than in DMF. This is ascribed to the different solvation number of the sodium ion in P Y and DMF, i.e., the sodium ion is coordinated with a smaller number of solvent molecules in the former solvent than in the latter. 
  Reference    Z. Naturforsch. 50b, 529—535 (1995); received September 12 1994 
  Published    1995 
  Keywords    Thermodynamics of Complexation, Sodium Complexes, 12-Crown-4, 18-Crown-6, Pyridine 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0529.pdf 
 Identifier    ZNB-1995-50b-0529 
 Volume    50