【摘要】 用电导法研究了甲醇溶液中Na~+,K~+,Rb~+,Cs~+与新合成的冠醚2,3-苯并-8,15-二甲基-18C6,2,3-苯并-8,11,15-三甲基-18C6以及苯并-15C5,18C6的配位作用,计算了1∶1配合物的稳定常数.18C6对碱金属离子具有显著的选择性,而其二甲基及三甲基取代物的选择性则较差.冠醚环上引入苯环及甲基使配合物的稳定常数降低,在甲醇中碱金属离子与18C6配合物稳定性次序为K~+>Rb~+>Cs~+>Na~+,2,3-苯并-8,15-二甲基-18C6配合物稳定性次序为K~+>Rb~+>Na~+>Cs~+,2,3-苯并-18,11,15-三甲基-18C6配合物稳定性次序为K~+>>Na~+>Rb~+>Cs~+.引入甲基对Na~+配合物稳定性的影响小于K~+,Rb~+,Cs~+,即阳离子半径对配合物稳定性有较大的影响.在所研究的浓度范围内,碱金属离子-冠醚体系当量电导的降低程度与按配合物结构的预测一致.本文结果为设计具有特定选择性的冠醚结构提供了线索.更多还原

【Abstract】 The coordination reaction of Na~+, K~+, Rb~+ and Cs~+ with benzo-l5-crown-5, 18-crown-6 and the newly synthesized cyclic polyethers 2, 3-benzo-8, l5-dimethyl-18-crown-6, 2, 3-benzo-8, 11, 15-trimethyl-18-crown-6 in methanol at 25℃ has been studied by conductometrio titration. The stability constants for the 1:1 coordination compounds were calculated. The marked selectivity of 18-crown-6 toward alkali metal ions was not found in its methyl derivatives. The induction effect of the benzene ring and methyl group on polyether ring reduced the stability of the coordination compounds. In methanol, the stability sequence of the compounds of alkali metal ions with 18-crown-6 was K~+>Rb~+>Cs~+>Na~+, that of its dimethyl derivative was K~+> Rb~+>Na~+>Cs~+ and that of its trimethyl derivative was K~+>Na~+>Rb~+>Cs~+, that is, the methyl substituent had a weaker influence on the stability of Na~+ compound than on that of Rb~+ or Cs~+ compound. In tne range of concentration studied, decrease in equivalent conductance is in agreement with the prediction on the basis of the structure of the complexes. The above results may give a clue for modifying the structure of a crown ether for specified selectivity.更多还原