Partition Coefficients and Equilibrium Constants of Crown Ethers between Water and Organic Solvents Determined by Proton Nuclear Magnetic Resonance

Abstract

The extraction of water by several crown ethers into chloroform + carbon tetrachloride mixtures has been investigated using a proton NMR technique. The equilibrium is well described by formation of a 1:1 water−crown complex in rapid exchange with uncomplexed ligand and water. The fraction (k) of crown ether complexed with water increases with crown cavity size, varying from (15 ±1)% for 12-crown-4 to (97 ± 5)% for 18-crown-6. Addition of carbon tetrachloride to chloroform lowers the k value for all crown ethers in equilibrium with water, and the value is close to zero in pure CCl4. The partition coefficient follows the opposite trend: the amount of crown ether in the organic phase increases with the percentage of CCl4 in this phase. The chemical shifts of free and complexed water also vary with solvent composition. Interaction of water with crown ether depends on solvation environment and may play a significant role in liquid−liquid extraction of metal ions using macrocyclic polyethers as extractants.

Synergistic Efficiency of 2-[(1-Aza-15-crown-5)-1-ylmethyl)]-4-(phenyldiazenyl)-naphthalen-1-ol in the Liquid Extraction of Light Lanthanoid(III) Ions with 4-Benzoyl-3-phenyl-5-isoxazolone: The Role of Aza-Crown and Azo-Dye Fragments on the Extraction Ability

“…Since the partition coefficients of the crown ether B15C5 used is known to be quite large, no corrections are necessary for the partitioning of this crown ether in the aqueous phase. , But the equilibrium concentration of 15C5 was calculated using the partition coefficient (log K D = 0.9) taken from the literature false[ normalS false] in = false[ normalS false] false( normalo false) + false[ normalS false] false( aq false) italicK normalD = false[ normalS false] false( normalo false) / false[ normalS false] false( aq false) goodbreak0em1em⁣ and goodbreak0em1em⁣ false[ normalS false] false( normalo false) = italicK normalD · false[ normalS false] false( aq false) false[ normalS false] false( normalo false) = false[ normalS false] in italicK normalD / 1 + italicK normalD …”

“…Since the partition coefficients of the crown ether B15C5 used is known to be quite large, no corrections are necessary for the partitioning of this crown ether in the aqueous phase. 5,40 But the equilibrium concentration of 15C5 was calculated using the partition coefficient (log K D = 0.9) taken from the literature. 5 a The values of the equilibrium constants are calculated on the basis of the 42 experimental points; the statistical confidence is 95 %, and the standard deviation is less than ± 0.05.…”

“…5,40 But the equilibrium concentration of 15C5 was calculated using the partition coefficient (log K D = 0.9) taken from the literature. 5 a The values of the equilibrium constants are calculated on the basis of the 42 experimental points; the statistical confidence is 95 %, and the standard deviation is less than ± 0.05.…”