69502-29-0Relevant academic research and scientific papers
Chemistry of crown ethers XIX. Functionalized crown ethers for the solubilization of barium sulfate
Jong, F. de,Zon, A. van,Reinhoudt, D. N.,Torny, G. J.,Tomassen, H. P. M.
, p. 164 - 173 (2007/10/02)
The use of seawater as injection fluid in oil-producing formations often leads to blocking of the wells as a result of barium sulfate-scale formation.Macrocylic complexants specifically designed to solubilize barium sulfate efficiently into water have been synthesized and their BaSO4-solubilizing capacities have been determined.The stability of barium complexes of macrocyclic polyethers can be greatly increased by the introduction of flexible side-chains containing anionic groups.Most of newly synthesized complexants, based mainly on diaza-18-crown-6, give very stable complexes.However, many o f them are extremely insoluble in water.Only bis(carboxymethyl)diaza-18-crown-6, bis(phosphonomethyl)diaza-18-crown-6 and, to a lesser extent, bis(dicarboxymethyl)diaza-18-crown-6 and bisdiaza-18-crown-6 are efficient solubilizers of BaSO4 in water.
Crown Ethers of Low Symmetry. Spiro Crown Ethers and 16-Crown-5 Derivatives
Ouchi, Mikio,Inoue, Yoshihisa,Sakamoto, Hidefumi,Yamahira, Atsushi,Yoshinaga, Masanobu,Hakushi, Tadao
, p. 3168 - 3173 (2007/10/02)
Spiro crown ethers 3a-c, spiro bis(crown ethers) 5a-e, and the related 16-crown-5 derivatives 6a-d were synthesized and their cation binding abilities were evaluated by study of the extraction of aqueous alkali picrates.Crown ethers carrying 13-crown-4 and 16-crown-5 skeletons showed significant changes in cation selectivity as compared with the corresponding 12-crown-4 and 15-crown-5.Spiro-13-crown-4 3a and spiro-bis 5a showed extremely low extractabilities for all cations examined, while the 16-crown-5-derivatives, including spiro-bis 5b and spiro-bis 5c, showed anomalously high Na+ selectivity.In a quantitative study of extraction equilibrium constants (Kex), 16-crown-5 was again found to have much higher selectivity for Na+ than 15-crown-5.This result is attributed to the less symmetrical spatial arrangement of donor oxygen atoms in 16-crown-5; the symmetry-extractability relationship is discussed on the basis of the size-fit concept.
Polytopic Cation Receptors. 2. Synthesis and Selective Complex Formation of Spiro-Linked "Multiloop Crown Compounds"
Weber, Edwin
, p. 3478 - 3486 (2007/10/02)
A new type of crown compound (1-10) featuring a spiro-linked assembly of two to four individual macrorings differing in ring size, rigidity, and donor characteristics is synthesized.Syntheses were achieved by means of high-dilution techniques and blocking/deblocking procedures beginning with pentaerythritol as the basic building block.The ability of the new ligands ("multiloop crown compounds") to selectively form crystalline polyhomonuclear/heteronuclear complexes is studied.It is found that the symmetrically looped molecules (1a-c, 4a, 6, 7d) can incorporate two orthree identical metal cations well matched in their diameter (Li+, Na+, K+, Ca2+, Ba2+).Cations which are too large to fit into the crown rings of 1a-c complex in a sandwich-like manner; those which are too small effect a high hydration in their complexes.Asymmetrical 1d and 9 allow the common uptake of different metal ions, e.g., a combination of Li+ and Ba2+ or of 2K+ and Co2+.The specific occupation of the different subrings is discussed.Ligand 1b is shown to discriminate Ca2+ from Na+; 1c and 6 preferentially complex Ba2+ from a Ba2+/K+ mixture.Thus, the new ligands act as manifold selective cation receptors, corresponding to the specification of their binding compartments.
