Cyclic ethers 1.3- dioxane

Chromium-Containing Ionic Species Chromate Ion, Hexavalent Chromium Cobalt Copper Cyclic Ethers Cyclic Ethers Dioxane-1,4 Ethylene Oxide... 

General Procedure. The selected electrolyte solution was placed in the jacketed reaction flask which was held at constant temperature by the connected circulating water bath. The tip of a buret containing the cyclic ether was introduced through a stopper into the mouth of the reaction flask. With the electrolyte solution undergoing constant stirring the cyclic ether was delivered slowly from the buret into the reaction flask to the point of turbidity or precipitation, and the delivered volume of cyclic ether was noted. The densities of the cyclic ethers (dioxane and THF) and of the electrolyte solutions used had been determined previously the normalities of the electrolyte solutions were known. With these data, the volume measurement of each of the components of the mixture was... 

Cole and Macritchie (1959) have used intensity measurements of the hydroxyl stretching absorption band at various temperatures to determine the energy of the hydrogen bond formed between a substituted cyclohexanol, frans-dihydrocryptol (XI), and a cyclic ether, dioxane (XII) in tetrachloroethylene solutions. The methods... 

The reaction between isobutylene (separated from C4 fractions from cracking units or from cracking isobutane to isobutene) and formaldehyde produces a cyclic ether (dimethyl dioxane). Pyrolysis of dioxane gives isoprene and formaldehyde. The formaldehyde is recovered and recycled to the reactor. 

For the most part, cyclic ethers behave like acyclic ethers. The chemistry of the ether functional group is the same, whether it s in an open chain or in a ring. Common cyclic ethers such as tetrahydrofuran and dioxane, for example, are often used as solvents because of their inertness, yet they can be cleaved by strong acids. 

Nakamiya K, S Hashimoto, H Ito, JS Edmonds (2005) Degradation of 1,4-dioxane and cyclic ethers by an isolated fungus. Appl Environ Microbiol 71 1254-1258. 

Bernhardt D, H Diekmann (1991) Degradation of dioxane, tetrahydrofuran and other cyclic ethers by an environmental Rhodococcus strain. Appl Microbiol Biotechnol 36 120-123. 

Heterocyclic compounds are frequently used as hydrogen donors in the reduction of C-C double and triple bonds catalyzed by complexes of transition metals. Cyclic ethers such as [l,4]dioxane (39) and 2,3-dihydrofuran are known to donate a pair of hydrogen atoms to this type of compound. 2,3-Dihydro-[l,4]di-oxine (41), the product of dioxane (39), is not able to donate another pair of hydrogen atoms [46, 60, 73, 74]. These heterocyclic compounds are in general also very good solvents for both the catalyst and the substrates. 

Insertion of the carbenes, via a low-lying singlet state close to the ground-state triplet, generated by photolysis of the diazo compounds (128), into the CO bond of cyclic ether solvents (THF, THP, dioxane) gave rise to polyether-bridged azulenes such as (129). ... 

Calvo, E., Brocos, P., Bravo, R., Pintos, M., Amigo, A., Roux, A.H., and Roux-Desgranges, G. Heat capacities, excess enthalpies, and volumes of mixtures containing cyclic ethers. 1. Binary systems 1,4-dioxane -r n-alkanes, J. Chem. Ene. Data, 43(1) 105-111, 1998. 

Leaist, D.G., MacEwan, K., Stefan, A., and Zamari, M. Binary mutual diffusion coefficients of aqueous cyclic ether at 25 °C. Tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, tetrahydropyran, and trioxane, J. Chem. Eng. Data, 45(5) 815-818, 2000. 

The ring-opening polymerization of cyclic ethers having 3-, 4-, and 5-membered rings (e.g., epoxides, oxetanes, THF) yields polymeric ethers. Six-membered rings (1,4-dioxane) are not capable of polymerization. 

Dinoseb sec-Butyl Dinitrophenol Dinitrophenol, 4,6-sec-butyl under Other Nitrophenols Dioxane-1,4 under Cyclic Ethers... 

If a cyclic ether such as dioxolane or dioxane is substituted for the acyclic ether the result is copolymerization of the cyclic ether (25) (Fig. 6). 

Certain cyclic ethers which will not homopolymerize will copolymerize with THF (25, 52). These cyclic ethers are stable five and six-membered ring compounds such as 2-methyltetrahydrofuran (2-MeTHF), and 1,4-dioxane (DOX). It is probable that 4-phenyl-l,3-dioxane (PhDOX), tetrahydropyran (THP), and 4-methyl-l,3-dioxolane (MDOL) which do not homopolymerize but which have been reported to copolymerize with BCMO (107, 108) would also copolymerize with THF. In the copolymerizations a correlation was again found between the basicity of the attacking ether and its reactivity with the cyclic oxonium ion. The... 

Peroxides in ether solvents. This is one of the commonest causes of explosions in organic chemistry laboratories. Simple dialkyl ethers such as diethyl ether and di-isopropyl ether, and cyclic ethers such as 1,4-dioxane and tetrahydrofuran, form less volatile peroxides on exposure to air and light. If therefore one of these solvents is purified by distillation, the peroxide content in the residue is progressively increased and eventually a violent explosion may occur. In view of this (i) such solvents should not be stored for long periods or in half empty bottles containers should be of dark glass (ii) before the solvents are distilled a peroxide test should be carried out, and, if positive, the peroxide must be removed (Section 4.1.11, p. 402 and Section 4.1.75, p. 404) and (iii) since purified ethers in contact with air rapidly peroxidise again (10 minutes in the case of tetrahydrofuran) they should be retested for peroxides and purified if necessary immediately before use. 

Cyclic solvents Dioxane, THF, Benzene, Toluene, Cyclohexane Acyclic solvents DMF, CH3CN, Ethyl acetate, Diisopropyl ether, Dibuthyl ether, Hexane... 

Cyclic ethers with larger rings than epoxides include tetrahydrofuran (THF), tetrahydropyran (THP), and dioxane. Large-ring cyclic polyethers, called crown ethers, can selectively bind metal ions, depending on the ring size. 

Know the meaning of cyclic ether, tetrahydrofuran, furan, tetrahydropyran, dioxane, crown ethers. 

The results of the Wurtz-like reaction depend on the reaction conditions. An important factor is the kind of solvent The ethers are generally better than hydrocarbons, but with the cyclic ethers like tetrahydrofuran (THF), dioxane and other frequently used agents, a cleavage reaction of the ethers was observed392. Hexamethylphosphoricacid amide was recently used with good results in combination with lithium497. ... 

Pentacene ethers 37-39 (Fig. 3.8) were prepared in an attempt to reduce the HOMO energy level relative to functionalized pentacene 29 [52]. These cyclic ether compounds were surprisingly stable, soluble and easily crystallized. Saturated diox-ane compound 37 has an oxidation potential of 0.580 V vs SCE (similar to that of unfunctionalized pentacene), but the axial hydrogen atoms on the dioxane ring prevent -stacking interactions in the crystal. Derivatives 38 and 39 were synthesized to overcome this structural issue. Although the change of oxidation potential... 

A major use of ethers in the organic laboratory is as solvents for reactions. Ethers are nonpolar enough to dissolve many organic compounds, and the electrons on the oxygen can interact with alkali metal cations to help solubilize salts. In addition, ethers are nonacidic and are not very reactive. For these reasons they are especially useful in reactions involving strongly basic reagents. In addition to diethyl ether, other ethers that are commonly used as solvents are 1.2-dimethoxyethane (DME) and the cyclic ethers tetrahydrofuran (THF) and 1,4-dioxane ... 

This section deals only with solvents whose reduction products are insoluble in the presence of lithium ions. The list includes open chain ethers such as diethyl ether, dimethoxy ethane, and other polyethers of the glyme family cyclic ethers such as THF, 2Me-THF, and 1,4-dioxane cyclic ketals such as 1,3-dioxolane and 1,3-dioxane, esters such as y-butyrolactone and methyl formate and alkyl carbonates such as PC, EC, DMC, and ethylmethyl carbonate. This list excludes the esters, ethyl and methyl acetates, and diethyl carbonate, whose reduction products are soluble in them (in spite of the presence of Li ions). Solutions of solvents such as acetonitrile and dimethyl formamide are also not included in this section for the same reasons. Figure 6 presents typical steady state voltammo-grams obtained with gold, platinum, and silver electrodes in Li salt solutions in which solvent reduction products are formed and precipitate at potentials above that of lithium metal deposition. These voltammograms are typical of the above-mentioned solvent groups and are characterized by the following features ... 

In many reactions molecular hydrogen may be replaced by other H-sources such as methanol, isopropanol, or formic acid even cyclic ethers such as dioxane or THF can be used in homogeneous transfer hydrogenation. The hydrogen donor coordinates to the metal and undergoes /3-hydrogen transfer ... 

Fuchigami and his co workers found that the fluorination of cyclic ethers like tet-rahydrofuran, 1,4-dioxane, and 1,3-dioxolane was achieved by anodic oxidation of a mixture of a large amount of liquid cyclic ethers and a small amount of Et4NF 4HF (only 1.5-1.7 equiv. of F to the ether) at a high current density (150 mA... 

According to Godneva and Klocho (13), when an electrolyte is added to water-dioxane or water-THF, two phases result. In order to bring about this separation, the water-cyclic ether association must be broken down. These authors believe that the hydration of the electrolyte cations is accomplished by the dehydration of the cyclic ether molecules, causing stratification. 

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