The first quantitative assessment of the individual processes involved in the extraction of alkali-metal picrates by ethyl p-tert-butylcalix(4)arenetetraethanoate in the water[ndash ]benzonitrile solvent system

Abstract

Partition and distribution constants of alkali-metal (lithium, sodium, potassium, rubidium) picrates in the waterÈbenzonitrile solvent system and ion-pair formation constants for these electrolytes in the water saturated organic phase at 298.15 K derived from distribution data are reported. Partition data are discussed with respect to transfer data for these electrolytes referred to the process involving the pure solvents. The extraction of alkali-metal picrates from water to benzonitrile by ethyl p-tert-butylcalix(4) arene tetraethanoate is investigated taking into account the extent of ion-pair formation of the alkali-metal complex salt in benzonitrile. A quantitative assessment of the individual processes which contribute to the overall extraction of alkali-metal picrates by the calixarene ester from water to benzonitrile is reported for the Ðrst time.

Extraction of Alkali-Metal Picrates by Calixarene Esters in the Water–Nitrobenzene Solvent System. The Medium Effect on the Partition and Extraction Processes

“…The same stoichiometry was found for other alkali-metal cations. It is also evident from this Figure that as far as sodium is concerned, Et Calix [4] is a better extracting agent for this cation than Et Calix [6]. The results obtained show that the latter ligand is a better extracting agent for the larger cations such as potassium, rubidium and caesium.…”

“…Thus Fig 2 shows the percentage of extraction (% E) for sodium picrate in the waternitrobenzene solvent system at 298.15 K against the ligand: anion ratio using Et Calix [4] and Et Calix [6]. In both cases, the stoichiometry of the process obtained from the intersection of the two lines (prior and after the 1:1 ligand: anion ratio) indicates that one metal cation is taken up per unit of ligand.…”

“…Calixarene esters, namely, ethyl p-tert-butyl calix [4]arene tetraethanoate, Et Calix [4] and ethyl p-tert-butyl calix [6]arene hexaethanoate, Et Calix [6] were synthesised following the procedure suggested by Danil de Namor and co-workers [8][9][10] .…”

“…The alkali-metal picrates were prepared 'in situ' by adding to a solution of picric acid in water (saturated with nitrobenzene), an excess of alkali-metal hydroxide or carbonate as described before . [4][5][6][7] .…”

“…Alkali-metal picrates were synthesised from picric acid (analytical grade, recrystallised as previously reported) [4][5][6][7] and the appropriate alkali-metal hydroxide (Li + , Na + , K + ) or carbonate (Rb + and Cs + ). The concentration of picric acid was determined by volumetric analysis.…”