Ethers, degradation

Xu XR, Gu J-D (2004) Elucidation of methyl ferf-butyl ether degradation with Fe2+/H202 by purge-and-trap gas chromatography-mass spectrometry. Micro-chemJ 77 71-77... 

Degradation of methyl terf-butyl ether by bifunctional aluminum in the presence of oxygen was investigated by Lien and Wilkin (2002). Bifunctional aluminum was synthesized by sulfating aluminum metal with sulfuric acid. When the initial methyl terf-butyl ether concentration was 14.4 mg/L, 90% of methyl ferf-butyl ether degraded within 24 h forming acetone, methyl acetate, tert-hniyX alcohol, and ferf-butyl formate. Carbon disulfide was tentatively identified as a reaction product by GC/MS. Product yields were 27.6% for acetone, 18.4% for methyl acetate, 21% for tert-hniyX alcohol, and 6.1% ferf-butyl formate. When the initial concentration of methyl tert-butyl ether was reduced to 1.4 mg/L, 99.5% of methyl terCbutyl ether reacted. Yields of acetone, methyl acetate, and /erf-butyl alcohol were 54.7,17.2, and 13.2, respectively. 

The API fenoprofen calcium is a diaryl ether. Degradation of fenopro-fen under intense ultraviolet light in solution yields a mixture of isomeric biphenyls via a photo-Fries rearrangement mechanism (Fig. 76) (117). 

Diethyl ether was found to be a much safer anesthetic than chloroform. Like chloroform, ether is more soluble in fatty tissue than in water, so it passes into the central nervous system and takes effect quickly. Ether is also volatile, making it easy to administer. But ether is much less toxic than chloroform because ether degrades to ethanol, which the body can oxidize. 

Chang PBL, Young TM (2000) Kinetics of Methyl lert-Butyl Ether Degradation and By-Product Formation During UV/Hydro-gen Peroxide Water Treatment, Wat. Res. 

Baehr A. L., Charles E. G., and Baker R. J. (2001) Methyl tert-butyl ether degradation in the unsaturated zone and the relation between MTBE in the atmosphere and shallow groundwater. Water Resour. Res. 37(2), 223. 

Petroleum ether degrades rapidly in soil and water. In air, it reacts with photochemically produced hydroxyl radicals with an estimated half-life of 4-8 days. Based on water solubility and estimated bioconcentration factors, petroleum ether is not expected to bioconcentrate in aquatic organisms. 

Hristova KR, Lutenegger CM, Scow KM (2001) Detection and quantification of methyl tert-butyl ether-degrading strain PMl by real-time TaqMan PCR. Appl Environ Microbiol 67 5154-5160... 

Granda (1964) has studied the sterol binding capacity of the protein phospholipid complex obtained after ether degradation of the low-density serum lipoproteins. In these experiments the water-soluble cholesterol-free lipoproteins were equilibrated with sterols dissolved in heptane. A rapid uptake of cholesterol was noted when human sera were examined this was not observed in chicken sera. 

Burns MA, Hanson JR, Mefford J, Scow KM (2001) Isolate PMl populations are dominant and novel methyl tert-butyl ether-degrading bacteria in compost biofilter enrichments. Environ Microbiol 3 220-225... 

Son A, Nichkova M, Dosev D et al (2008) Luminescent lanthanide nanoparticles as labels in DNA microarrays for quantification of methyl tertiary butyl ether degrading bacteria. J Nanosci Nanotechnol 8 2463-2467... 

Indyk [705] studied the tocopherols, stigmasterol, and cholesterol extracted from milk powder on a Cjs column (A = 295 run, ex 330 nm, em for tocopherols, or 212 nm UV detection for all other analytes). Elution was complete in 30 min when a 99.9/0.1 hexane/IPA mobile phase was used. Detection limits were given as 0.04 xg/injection and 4 mg/kg sample (cholesterol). The author noted that the use of isopropyl ether as the extraction solvent caused problems with the chromatography. Baseline disturbances were reported to occur early in the chromatogram, in the region where the tocopherols eluted, most likely due to the elution of diisopropyl ether and diisopropyl ether degradation components. 

The method of differential radiation induced contrast depends on enhancement of contrast in multicomponent polymers where the components have different electron beam-polymer interactions [173]. Contrast has been observed in sections of styrene-acrylonitrile/poly(methyl methacrylate) (SAN/PMMA) polymers where the PMMA exhibits a high rate of mass loss compared to SAN, creating contrast between the phases. It is well known that electron irradiation results in chain scission and crosslinking, loss of mass and crystallinity [75]. Polystyrene, polyacrylonitrile and SAN crosslink and thus are stable in the electron beam whereas polymers exhibiting chain scission, PMMA and poly(vinyl methyl ether), degrade in the beam. It is suggested that experiments be conducted on the homopolymers to determine the expected irradiation damage mechanism in the multi-component system [173]. 

Keywords Arylcalcium Calcium Diarylcalcium Ether degradation Organylcalcium Post-grignard reagents... 

Scheme 3 Ether degradation of tetrahydrofuran (top) and diethyl ether (middle and bottom) after initial deprotonation in a- or p-position...

Arylcalcium complexes are commonly prepared in ethereal solutions via reduction of aryl halides with finely divided and highly reactive calcium powder. Because diethyl ether has a rather low boiling point these exothermic reactions are advantageously carried out in tetrahydrofuran (THF) or tetrahydropyran (TEfP). Due to an operative Schlenk equilibrium usually three species are present in solution heteroleptic [(Ar) CaI(L) ] as well as homoleptic [Cal2(L) ] and [(Ar)2Ca(L)J. Fractionated crystalh-zation and subsequent recrystallization are mandatory in order to remove excess of calcium, imreacted substrates, and ether degradation products. 

The initial deprotonation of THF and diethyl ether as initial step of ether degradation clearly demonstrates the depronative power of calcium-based post-Grignard... 

Fig. 7 Schematic drawings of ether degradation products oxygen-centered Ca4 tetrahedron with bridging phenyl groups and iodide anions (left), oxygen-centered Cag octahedron with vinylate anions above the planes (middle), 0404 heterocubane with Cal2 bound at the periphery of the cubane cage. In all these cages vacant sites at calcium are occupied with thf ligands...

Temperatures below ambient temperatures have to be maintained in order to avoid side reactions such as ether degradation. For the same reason excess of calcium metal should be removed after the preparation of post-Grignard reagents. 

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