Ethers, aliphatic oxidation

The tendency of aliphatic ethers toward oxidation requires the use of antioxidants such as hindered phenoHcs (eg, BHT), secondary aromatic amines, and phosphites. This is especially tme in polyether polyols used in making polyurethanes (PUR) because they may become discolored and the increase in acid number affects PUR production. The antioxidants also reduce oxidation during PUR production where the temperature could reach 230°C. A number of new antioxidant products and combinations have become available (115,120,124—139) (see Antioxidants). 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Furthermore, the mediator has been used for the bond cleavage of benzyl ethers, the oxidation of benzyl alcohol to benzaldehyde, the oxidation of toluene derivatives to benzoic acid esters, and the oxidation of aliphatic ethers [47]. 

Poly(ethylene oxide) Water, toluene, DMF Methanol, diethyl ether, aliphatic hydrocarbons... 

Grosjean, D., Atmospheric Chemistry of Toxic Contaminants. 2. Saturated Aliphatics Acetaldehyde, Dioxane, Ethylene Glycol Ethers, Propylene Oxide, J. Air Waste Manage. Assoc., 40, 1522-1531 (1990b). 

At least three methods have been found to be applicable to the solubilization of chemically modified wood. The first experiment (4) (Direct method) employed severe dissolution conditions. For example, in 20-150 min at 200-250°C, wood samples esterified by a series of aliphatic acids could be dissolved in benzyl ether, styrene oxide, phenol, resorcinol, ben-zaldehyde, aqueous phenol solutions, etc. For carboxymethylated, ally-lated and hydroxyethylated woods, the conditions provided for dissolution in phenol, resorcinol or their aqueous solutions, formalin, etc., by standing or stirring at 170°C for 30 to 60 min (5). 

Aliphatic primary silyl ethers are oxidized, probably via an aldehyde or acetal, to the simple esters formed from two equivalents of the silyl ethers (equation I). When a mixture of an aliphatic aldehyde and a primary silyl ether are oxidized under the... 

The first trial of the liquefaction of wood was accomplished by using very severe dissolving conditions [10]. One example used wood samples esterified with a series of aliphatic acids, which could be liquified in benzyl ether, styrene oxide, phenol, resorcinol, benzaldehyde, aqueous phenols, a chloro-form-dioxane mixture, or a benzene-acetone mixture after treating at 200-270°C for 20-150 min. 

Saturated aliphatic ethers are oxidized in AcOH/MeOH containing Et4NOTs or Bu4NBp4. ... 

A second problem with Sarett oxidation is the difficulty in isolating the products from a pyridine solution. An advantage of the technique, as mentioned above, is that alkenes, ketals, sulfides, and tetrahydropyranyl ethers are oxidized much slower than alcohols and rarely give competitive side reactions. Oxidation of secondary alcohols proceeds in good yield, but oxidation of primary aliphatic alcohols often gives low yields of the aldehyde. 2 Benzylic and allylic alcohols give good yields, however. 

Structure and functional group H3C—O— CH3 first member of a homologous series of aliphatic ethers, containing two methyl groups linked via an oxygen atom Synonyms dimethyl ether wood ether dimethyl oxide... 

CH=CH2, an aliphatic ether containing two oleflnic double bonds Synonyms divinyl ether divinyl oxide 1,L-oxybis(ethene) ethenyloxyethene... 

Chloro-substituted aliphatic ether Syuouyms 2,2 -dichloroethyl ether di(2-chloroethyl)ether dichloroethyl oxide 1, F-oxybis(2-chloroethaue)... 

Synonyms Anesthetic ether Diethyl ether Diethyl oxide Ether Ethoxyethane Ethyl oxide 1,1 -Oxybisethane Oxybis-1,1-ethane Solvent ether Sulfuric ether Classification Sat. aliphatic ether Empirical C4H10O Formula CH3CH2OCH2CH3... 

Properties Colorless clear vise, liq., si. bitter taste sol. in water, aliphatic ketones, alcohol insol. in ether, aliphatic hydrocarbons m.w. 400-2000 dens. 1.001 -1.007 m.p. does not cryst. flash pt. > 390 F Toxicology LD50 (oral, rat) 4190 mg/kg mildly toxic by ingestion skin and eye irritant linked to sensitive reactions TSCA listed Precaution Combustible exposed to heat or flame reactive with oxidizers... 

Total content (at.%) Functional groups 22 Ether Carbonyl Oxide 41 Aliphatic Ether Carbonyl 12 Ru° Ru ... 

Toxicity of the polyamines can, however, be avoided by using modified aliphatic polyamines. These are obtained by the addition of polyamines to a variety of compounds such as diglycidyl ether, ethylene oxide, styrene oxide, halohydrin ethers and acrylonitrile or with polymers containing functional groups known to react with amines (other than epoxides). 

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