Department of Chemistry, Shiraz University, Shiraz, I.R. IRAN
The interaction between hydronium ion and several crown ethers was studied via conductometry in nitromethane at 25 °C and 1H-NMR techniques. The stabilities of the resulting 1:1 complexes were determined from the conductance data and found to vary in the order DC18C6 > 18C6 > DB30C10 > DB24C8 > DB18C6 > ~B15C5 > DB21C7. For the first time, evidences for the formation of a 2:1 sandwich complex between the smaller crown ethers (i. e. B15C5 and 18 crowns) and hydronium ion in solution were observed by monitoring the molar conductance of hydronium ion as a function of the ligand to cation mole conductance of hydronium ion as a function of the ligand to cation mole ratio. The 1H-NMR data support the existence of such 2:1 adduct in solution.