Presence Of Crown Ether Research Articles

Kinetics of reaction of phosphorus acid esters with alcoholates in the presence of crown ether

1. The reactivity of free anions and ionic pairs of alcoholates was studied in reactions with phosphorus acid esters in alcoholic solutions. 2. Addition of 18-crown-6 to the reaction mixture causes acceleration of the reactions of esters having a thiophosphoryl group and slowing down of the reaction with esters having a P=0 group. 3. The rate constants of the reactions with the participation of ions and ionic pairs increase on transition from lower to higher alcohols. The difference between the reactivity of the ionic pairs and that of the free anions of the alcoholates increases in the same direction also.

ChemInform Abstract: f‐Element/Crown Ether Complexes. Part 10. Oxidation of UCl4 to (UO2Cl4)2‐ in the Presence of Crown Ethers: Structural Characterization of Crown Ether Complexed Ammonium Ions ((NH4)(15‐crown‐5)2)2(UO2Cl4)·2 CH3CN, ((NH4)(benzo‐15‐crown‐5)2)2(UCl6)·4 CH3CN, and ((NH4)(dibenzo‐18‐crown‐6))2(UO2Cl4)·2 CH3CN and Synthesis of (Na(12‐crown‐4)2)2(UO2Cl4)·2 OHMe and (UO2Cl2(OH2)3)·18‐crown‐6·H2O·OHMe

ChemInformVolume 19, Issue 16 Organoelement Compounds ChemInform Abstract: f-Element/Crown Ether Complexes. Part 10. Oxidation of UCl4 to (UO2Cl4)2- in the Presence of Crown Ethers: Structural Characterization of Crown Ether Complexed Ammonium Ions ((NH4)(15-crown-5)2)2(UO2Cl4)·2 CH3CN, ((NH4)(benzo-15-crown-5)2)2(UCl6)·4 CH3CN, and ((NH4)(dibenzo-18-crown-6))2(UO2Cl4)·2 CH3CN and Synthesis of (Na(12-crown-4)2)2(UO2Cl4)·2 OHMe and (UO2Cl2(OH2)3)·18-crown-6·H2O·OHMe R. D. ROGERS, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this authorL. K. KURIHARA, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this authorM. M. BENNING, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this author R. D. ROGERS, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this authorL. K. KURIHARA, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this authorM. M. BENNING, Dep. Chem., North. Ill. Univ., DeKalb, IL 60115, USASearch for more papers by this author First published: April 19, 1988 https://doi.org/10.1002/chin.198816280Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue16April 19, 1988 RelatedInformation

Anionic Grafting of Polystyrene from Carbon Blacks Catalyzed by Oli Groups on the Carbon Black Surface in the Presence of Crown Ether

Abstract Carbon black carrying OLi groups, which was prepared by the reaction of the oxygen-containing groups on the surface with n-butyllithium (BuLi), was unable to initiate anionic polymerization of styrene. However, anionic polymerization of styrene is initiated by OLi group on carbon black in the presence of a crown ether, such as 12-crown-4 and 18-crown-6. Then polystyrene was effectively grafted from carbon black owing to the propagation of polystyrene from the OLi groups. The grafting ratio increased with increasing amount of BuLi used for pretreatment of the carbon black and was a maximal (170%) in the presence of carbon black pretreated with BuLi in a quantity equivalent to its oxygen-containing groups. When carbon black was pretreated with excess BuLi, i.e., in the presence of free BuLi, the grafting ratio decreased to less than 20% because the formation of ungrafted polystyrene by free BuLi occurs preferentially to the propagation from the OLi groups on carbon black. Furthermore, it was found ...

Synthesis of the complex aluminum hydrides M+Al2H7 ? (M+=Li, Na, K) and a study of their transformations

When lithium, sodium, and potassium aluminum hydrides react with an ether solution of AlH3 in the presence of crown ethers, complexes are formed that contain the Al2H7− anion.

Extraction of alkali metal cations into polyester-based polyurethane foam using crown ether and picric acid

The distribution of alkali metal picrates between water and polyester-based polyurethane foam in the presence of dicyclohexyl-18-crown-6 was studied. The order of extraction coefficients of the alkali metals is governed by the ratio of the cation size to that of the crown ether, although the degree of extraction may depend on the nature of the organic phase. The extraction of alkali metals by polyurethane foam from an aqueous solution in the presence of crown ether and a bulky anion can be considered as an ion pair extraction of MCrA by an organic solvent.

Potassium ion transport processes across the interface of an immiscible liquid pair in the presence of crown ethers

The mechanism of potassium ion transfer from an aqueous to a 1,2-dichloroethane phase which is facilitated by urushiol crown ether or dibenzo-18-crown-6 in the range of potassium concentrations, c K + , from 0.1 m M to 1 M was studied by current scan polarography at the ascending water electrode, chronopotentiometry, and chronopotentiometry with current reversal at the stationary water electrode. At c K + below 0.02 M a single polarographic wave is obtained, which corresponds to the transfer of K + -crown ether complex from the aqueous phase. At c K + ≥ 0.02 M , an additional wave appears at a less positive potential which grows at the expense of the first wave, which finally disappears at higher c K + . The second wave results from the transfer of a simple potassium ion across the interface, where it reacts with the crown ether. At c K + at which the additional wave begins to appear, the formation reaction of K + -crown ether takes place at the aqueous side of the interface.

Extraction of alkaline-earth metal ortho- and para-nitrophenoxides from aqueous media by crown ether and cryptand complexing agents

A study has been performed on the extraction of alkaline-earth metal ortho- and para-nitrophenoxides, from aqueous medium into methylene chloride, in the presence of crown ether and cryptand complexing agents. The results are analyzed in terms of the various constituent complexation and extraction equilibria involved. Comparison is drawn with our previously reported study on extraction of potassium p-nitrophenoxide. The different anion stoichiometries in the two systems result in relatively more favorable extraction of M+ systems at low anion concentrations. Furthermore, while extraction of MX (X = o- or p-nitrophenoxide) can be carried out in the presence of excess MOH, this is not possible in the case of MX2 due to the limited solubility of M(OH)2. The addition of excess MOH leads to more efficient extraction of M+-phenoxides and prevents hydrolysis to free phenols. A noteworthy point in both MX and MX2 systems is that at high concentrations of complexing agent a saturation effect occurs, which limits the overall extent of extraction achievable. Under these conditions the extraction is governed by the equilibrium constant, Kdcs, representing the partitioning of the complexed salt between the aqueous and organic phases, and is independent of the amount of ligand present.

Coordination compounds of divalent lanthanides with crown ethers

New complexes LnI 2·18-crown-6 (Ln-Sm, Tm, Dy, Nd) and LnJ 2·dibenzo-18-crown-6 (Ln-Sm, Tm) were synthesized using the solutions of LnI 2 in THF. The compounds obtained oxidize quickly in air, but are relatively stable in an inert atmosphere. The Tm 2+ complex is decomposed by light. The compounds obtained are poorly soluble in THF, the Sm 2+ and Tm 2+ compounds are soluble in CH 3CN, forming solutions with a period of half oxidation of 170 h and 6 min, respectively. Iodide ions of the complexes can be substituted for Cl − during treatment of the compounds by solution of LiCl in THF. The reflection spectra of the compounds synthesized are similar to the absorption spectra of Ln 2+ in THF, although a shift of bands towards the short wave region is observed. The study of the Ln 2+ oxidation kinetics in H 2O, CH 3CN, THF in the presence of crown ethers has shown that their stability is influenced not only by the type of solvent, relative solubility and stability of complexes Ln 2+ and Ln 3+, but also by phenyl groups, and by decreasing stability of Dy 2+ and Nd 2+.

Interaction of chloroaromatic compounds with alkali metal fluorides in the presence of crown-ethers

The influence of various crown-ethers on the reactions of polychloroaromatic compounds with alkali metal fluorides (KF, RbF, CsF) has been studied. It is shown that the catalytic effect of the crown-ether is almost independent of the nature of the polychloroaromatic substrate and that it is most effective only in a definite range of reaction rates.

Dehydrochlorination of polyvinylidene chloride (PVDC) in the presence of crown ether as a phase transfer agent

AbstractFilms of polyvinylidene chloride (PVDC) were heterogeneously dehydrochlorinated by reacting them with KF‐crown and KOH‐crown complexes dissolved in benzene. Solutions were in contact with an excess of unhydrous salts. This three‐phase reaction was very fast at 80°C and the removal of one chlorine atom per monomer unit was completed within 1 h. Further dehydrochlorination leads to triple‐bond formation and to aromatization of the system due to the intramolecular 1,6 elimination. The former reaction is dominant when KOH‐crown is used as the dehydrochlorinating agent and the latter is dominant in KF‐crown/CaO systems. The apparent energy of activation of the initial dehydrochlorination process is estimated to be 6.7 kcal./mol.

Preparation of pyrazoles and pyrazolines by the reaction of chlorocyclopropanols with hydrazines in the presence of crown ethers

The reaction of gem-dichlorocyclopropanol with hydrazine and phenylhydrazine in the presence of crown ethers at 20‡C leads to the formation of the corresponding pyrazoles in yields up to 60%. Under analogous conditions, cis- and trans-chlorocyclopropanols and phenylhydrazine give N-phenylpyrazoline in 58% yield.

The Chemistry of Phthalide-3-carboxylic Acid. II. Decarboxylation of Salts in the Presence of Aldehydes

Salts of phthalide-3-carboxylic acid decarboxylate in the presence of aromatic aldehydes to give mixtures of the 3-( arylhydroxymethyl ) phthalide (2) and the 2-aryl-3-hydroxyindenone (3). The former may be obtained exclusively in the presence of the weak proton donor, triethyl (2-phenylethyl)ammonium chloride, and the latter in the presence of crown ethers or after longer reaction times. A study of the effect of different cations allows a mechanism to be deduced.

Cyclic Carbonates Obtained by Reactions of Alkali Metal Carbonates with Epihalohydrins

Abstract A study has been carried out on the reaction of alkali metal carbonates with epihalohydrins in the presence of cation complexing agents e.g. crown ethers. 3-Glycidyloxypropylene carbonate was found to be formed as the main product of the reaction of epichlorohydrin with potassium carbonate promoted by 18-crown-6. The effect of various epihalohydrins and alkali metal carbonates on the reaction course was examined. It was found that the reaction of potassium hydrogencarbonate with epichlorohydrin gives 4-hydroxymethyl-1,3-dioxolan-2-one. When the reaction of epihalohydrins with potassium carbonates was carried out in the atmosphere of carbon dioxide the products contained linear carbonate linkage apart from cyclic one. From these results, a plausible mechanism was proposed for the reaction of alkali metal carbonates with epihalohydrins in the presence of crown ethers.

Comparative extraction studies of potassium phenoxide, p-nitrophenoxide, and picrate into methylene chloride by macrocyclic crown ether and cryptand complexing agents

The results of a comparative extraction study of potassium phenoxide, p-nitrophenoxide, and picrate, from aqueous medium into methylene chloride in the presence of crown ether and cryptand complexing agents, are reported. The efficiency of extraction varies extremely widely with the nature of the anion and the ligand. An analysis of the results in terms of constituent equilibrium constants, and the factors which influence these, is presented. The significance of the results to other areas including phase transfer catalysis is pointed out.

Analytical applications of crown ethers: II. Oxidation and determination of aldehydes

The oxidation of aldehydes by dicyclohexyl-18-crown-6-potassium permangante complex is presented. Results obtained by this procedure showed that the presence of crown ether (DCC) and the catalyst play an important role in the oxidation of the aldehydes. The stoichiometry found corresponds to 2 μeq of permanganate per 1 μmol of aldehydes in all cases. Alcohols and ketones are not oxidized. Finally, a method for quantitative evaluation of aldehydes is proposed.

Analytical applications of crown ethers: III. Extraction and determination of nitrophenol isomers

Extraction of nitrophenols from water samples into benzene has been studied. The extraction is quantitative in the presence of crown ether when the pH of the aqueous phase is in the range 4.7 to 5.7. Beer's law is valid and a spectrophotometric determination of the nitrophenols is proposed.

Graft Copolymerization of Pyrrolidone onto Copolymers of N-Acryloyl Pyrrolidone and Vinyl Monomers

Abstract The copolymerizations of N-acryloyl pyrrolidone (NAP) with vinyl monomers methyl methacrylate (MMA), acrylonitrile (AN) and acrylamide (AA) were carried out in dimethylformamide at 65°C using 2,2′-azobisisobutyronitrile(AIBN) as an initiator. The resulting copolymers were used as a polymeric initiator of the anionic graft copolymerization of 2-pyrrolidone. The percent grafting of 2-pyrrolidone onto vinyl copolymer backbone chain involving N-acyllactam groups was found best with copoly(NAP-co-MMA) when the KOH concentration was 0.03 M. The presence of crown ether increased the viscosity of graft copolymers and accelerated the initial rate of anionic graft copolymerization.

Incorporation of lithium into gallium phosphide electrodes from lithium salt electrolytes in the presence of crown ethers

Anodic stripping analysis of cathodically polarized n- and p-type Gap electrodes has revealed that incorporation of lithium into a surface region of the electrodes takes place in aqueous electrolytes containing lithium salts and crown ethers such as 15-crown-5. Changes in spectral response of p-type electrodes caused by cathodic polarization in such electrolytes give support to the lithium incorporation. The redox potential for the incorporation reaction was estimated to lie somewhere between −1.95 and −0.91 V vs. SCE. The roles of crown ethers in the incorporation reaction are discussed.

Structures and ambident reactivity of β-ketoenolates ion pairs

The relationships between the conformations and ambident reactivity of alkali ethylacetoacetate ion pairs are discussed. The structures of these enolates are determined in the solid state and in solution, in the presence of crown ethers and cryptands. The lithium ethylacetoacetate triple anion exhibits a peculiar structure and extra stability.

Densitometric Determination of C-18 Fatty Acids as Phenacyl Esters Following Reversed-Phase Thin Layer Chromatography

Abstract A simple method of quantitatively determining C-18 fatty acids in an aqueous oxidized polyethylene emulsion is presented, utilizing the formation of phenacyl esters in the presence of crown ether as catalyst, followed by separation by reversed-phase thin layer chromatography, and subsequent densitometry of the strongly ultraviolet absorbing separated compounds. The method has good sensitivity, permitting the detection of as little as 5 nanomoles or less of fatty acids, and is applicable to various biological mixtures and to acids of different chain lengths.