Halogenated ethers

Ethers are either aliphatic (chain-structure) or aromatic (ring-structure) hydrocarbons containing an oxygen atom connected to two carbon atoms by single bonds. In halogenated ethers, one or... 

Typically, solvents are screened to identify one that gives optimal results. Assuming that the substrate and catalyst are soluble, solvent polarities varying from alkanes, aromatics, halogenated, ethers, acetonitrile, esters, alcohols, dipolar aprotic to water have been used. An example of this, using a ketone and the rhodium cp TsDPEN catalyst, is shown in Table 35.3. Further optimization of this reaction improved the enantiomeric excess to 98%. A second example involved the reduction of 4-fluoroacetophenone in this case the enantioselectivity was largely unaffected but the rate of reduction changed markedly with solvent. Development of this process improved the optical purity to 98.5% e.e. 

The electroreductive cyclization of the halogenated ether (169) or a halo-genated ester using Ni(II) complexes (171) and (172) proceeds in the manner shown in Scheme 69 [286]. The radical... 

Halogenated Aromatic Compounds Halogenated Cresols Halogenated Ethers and Epoxides Halogenated Phenolic Compounds Halophenols Chlorophenol Dichlorophenol Halophenols Pentachlorophenol PCP Tetrachlorophenol Trichlorophenol... 

Reaction of Trihalomethyl Compounds and Halogenated Ethers with Alkoxides or Carboxylates to Give... 

Sram RJ, Samkova I, Hola N. 1983. High-dose ascorbic prophylaxis inworkers occupationally exposed to halogenated ethers. J Hyg Epidemiol Microbial Immunol 27 305-318. 

The most common anesthetic gases are halogenated ethers. Notice the theme-and-variation relationship between these compounds. Researchers moved and exchanged halogen atoms around on the same basic skeleton in a systematic attempt to fine-tune the physiological properties of the substance. Figure 11.26 lists some common anesthetic ethers. 

Callahan, M.A., Slimak, M.W., Gabel, N.W., May, I.P, Fowler, C.F., Freed, J.R., Jennings, P., Durfee, R.L., Whitemore, F.C., Maestri, B., Mabey, W.R., Holt, B.R., Gould, C. (1979) Water-Related Environmental Fate of 129 Priority Pollutants. Vol.II, Halogenated aliphatic hydrocarbons, halogenated ethers, monocyclic aromatics, phthalate esters, polycyclic aromatic hydrocarbons, nitrosoamines and miscellaneous compounds. LPAH40/4-79-029b. 

V.F. Simmon, and R.l. Mazze. Mutagenicity of halogenated ether anesthetics. Anesthesiology 46 346-350, 1977. 

Ether and halogenated ether (isoflurane, enflurane, methoxyflurane, desflurane, sevoflurane, and fluroxene)... 

EPA. 1979. Water-related environmental fate of 129 priority pollutants. Vol. II Halogenated aliphatic hydrocarbons, halogenated ethers, monocyclic aromatics, phthalate esters, polycyclic aromatic hydrocarbons, nitrosamines, miscellaneous compounds. U.S. Environmental Protection Agency, Washington, DC. EPA-440/4-79-029B. 

TABLE 10.2.1 Summary of physical properties of ethers and halogenated ethers Molecular Molecular weight, MW Compound CAS no. formula g/mol m.p. °C b.p. °c Fugacity ratio, F at 25°C Density, p g/m at 20°C Molar volume, cmVmol Vm... 

TABLE 10.2.2 Summary of selected physical-cl Compound lemical properties of ethers and halogenated ethers at 25°C Selected properties ... 

A Aliphatic ethers Halogenated ethers o Aromatic ethers... 

Difunctional compounds, including certain halogenated ethers, aldehydes, ketones, phenols, amines, and nitro compounds, have been prepared by the Sandmeyer reaction. However, fluorophenols and fluoro acids are best obtained from the corresponding ethers and esters, respectively, which have been fluorinated by the Schiemann reaction. ... 

The a-position of an ether is susceptible to attack by free radicals and, in certain circumstances, by halogens. Ethers are slowly oxidized by the oxygen from air to form peroxides- This can be a hazard in stored bottles of ethers, particularly with the higher ethers such as di-isopropyl ether. These peroxides may be destroyed by treatment with iron(IT) sulfate. Chlorine reacts with ethers, particularly in sunlight. These a-halo ethers then decompose to the aldehyde and an alcohol. 

N gnesium bromide N gnesium chloride.etherate Hydrocaibons, halogenated Hydrocarbons, halogenated, ethers Moderate Moderate... 

---