Extractants ether linkage

Poloxamers are used primarily in aqueous solution and may be quantified in the aqueous phase by the use of compleximetric methods. However, a major limitation is that these techniques are essentially only capable of quantifying alkylene oxide groups and are by no means selective for poloxamers. The basis of these methods is the formation of a complex between a metal ion and the oxygen atoms that form the ether linkages. Reaction of this complex with an anion leads to the formation of a salt that, after precipitation or extraction, may be used for quantitation. A method reported to be rapid, simple, and consistently reproducible [18] involves a two-phase titration, which eliminates interferences from anionic surfactants. The poloxamer is complexed with potassium ions in an alkaline aqueous solution and extracted into dichloromethane as an ion pair with the titrant, tet-rakis (4-fluorophenyl) borate. The end point is defined by a color change resulting from the complexation of the indicator, Victoria Blue B, with excess titrant. The Wickbold [19] method, widely used to determine nonionic surfactants, has been applied to poloxamer type surfactants 120]. Essentially the method involves the formation in the presence of barium ions of a complex be-... 

Pure d-menthyl-Z-menthoxyacetate is hydrolyzed by refluxing for an hour with 1.2 mole equivalents of 5-10% ethanolic potassium hydroxide. (More vigorous hydrolysis is inadvisable since 1-menthol may thus be formed from the resolving agent by rupture of the ether linkage.) The mixture is almost neutralized to phenolphthalein with hydrochloric acid and is distilled with steam to remove first the ethanol and then the menthol. The menthol is conveniently extracted with benzene and purified by distillation under reduced pressure. It has b.p. 97-99°/10 mm., 215-2167760 mm. m.p. 42° and [aft0 + 49.5°(c = 2, 95% ethanol). The yield in this step is 80-85%. 

Water extraction studies of the carbohydrate modified resins in the earlier study indicate that a portion of the carbohydrate is apparently incorporated into the final cured resin. The absolute amount of modifier incorporated into the cured resin increases with the amount initially added during resin formulation. IR studies indicated that the carbohydrate derivative is probably incorporated into the resin via ether linkages. 

The addition of an ether linkage in the alkyl chains of dialkylphosphoric acids has been found to increase its extractive power for trivalent actinides, resulting in an extractant that is more effective from acid solutions than is HDEHP (69). Bis(hexoxy-ethyl)phosphoric acid (HDHqEP) is a compound of this type that has been studied extensively (70,71). The ether linkage may contribute to the coordination of the metal ion, resulting in the formation of a seven-membered ring. 

The formation of ether-type polar lipids that occur in the membranes of Archaea remains elusive. The enantiomeric glycerol-phosphate backbone, ether linkages, and isoprenoid chains are distinguishing features of archaeal lipids. Carbonaceous meteorites contain up to several percent of their mass as organic carbon, mainly polycyclic aromatic hydrocarbons. Material extracted from the Murchison meteorite by organic solvents contains amphiphiles that form membrane-like vesicles in aqueous solution. 

Dimers are a class of compounds isolated from only seven species of Celastraceae family [8,88]. These triterpene dimers were found to be composed of one quinoid type and one aromatic type of triterpene derived from pristimerin, tingenone and / or their congeners joined together by two ether linkages formed between the two A rings or between the A and B rings. From the methylene chloride soluble portion of a methanolic extract of Maytenus chuchuhuasca, four dimeric compounds were isolated by Shirota et al. [88]. 

Indole-alkaloid isoprenoid was isolated from extracts of Penicillium crustosum grown on rice. This compound, designated thomitrem (53), contains a 18(19)-double bond and lacks the characteristic penitrem 17(18)-ether linkage [100],... 

Prior to the synthetic preparation of thyroxine, hypothyroidism was treated with extracts of dried thyroid glands from animals. Standardisation was however not easy, and the use of these nutritional supplements caused occasionally serious side-effects. Industrial manufacturing of the pure hormone began around 60 years ago. Its synthetic challenges consist in the formation of the diphenyl ether linkage and the iodination of the aromatic rings. [89]... 

High-resolution mass spectroscopic analyses of pyridine extracts from reduced and untreated coals support the concept that ether linkages exist in the coal and are split during hydrogenation and that hydroaromatic compounds can be formed by addition of hydrogen to the aromatic nuclei. 

A major problem with the separation of metal ions using extraction or membrane systems is the slow but steady loss of the expensive macrocyclic compounds from the organic membrane or layer. To circumvent this problem, we have attached various macrocyclic compounds to silica gel using a stable hydrocarbon-ether linkage [7,14,15]. Log values for the interaction of these silica gel-bound macrocycles towards various metal ions were found to be the same ( 10%) as those for the analogous unbound macrocycles toward the same cations in water. This paper describes the synthesis of some of these silica gel-bound macrocycles, their metal ion complexation properties, their use in the separation and concentration of certain cations from cation mixtures and the potential use of silica gel-bound chiral macrocycles for the separation of enantiomeric ammonium salts. 

Up to now this reaction has only been observed with extracts of potato tubers. The 9-hydroperoxy isomers of linoleic and linolenic acids appear to be the exclusive substrates for the reaction. During the reaction one of the hydroperoxy oxygen atoms is inserted into the fatty acid chain to form a divinyl ether linkage. The products from linoleic and linolenic acids have been termed colneleic and colnelenic acids, respectively (5) (Fig. 2). 

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