Q. Luo
1983
Citations
0
Influential Citations
1
Citations
Journal
Acta Chimica Sinica
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.