Oxygen dimethyl ether reactions

Tetrafluoroethylene Oxide TFEO has only been prepared by a process employing oxygen or ozone because of its extreme reactivity with ionic reagents. This reactivity may best be illustrated by its low temperature reaction with the weak nucleophile, dimethyl ether, to give either of two products (47) (eq. 10). 

Oxygenates and Chemicals A whole host of oxygenated products, i.e., fuels, fuel additives, and chemicals, can be produced from synthesis gas. These include such produc ts as methanol, ethylene, isobutanol, dimethyl ether, dimethyl carbonate, and many other hydrocarbons and oxyhydrocarbons. Typical oxygenate-producing reactions are ... 

Active Figure 2.5 The reaction of boron trifluoride, a Lewis acid, with dimethyl ether, a Lewis base. The Lewis acid accepts a pair of electrons, and the Lewis base donates a pair of nonbonding electrons. Note how the movement of electrons from the Lewis base to the Lewis acid is indicated by a curved arrow. Note also how, in electrostatic potential maps, the boron becomes more negative (red) after reaction because it has gained electrons and the oxygen atom becomes more positive (blue) because it has donated electrons. Sign in atwww. thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

As was the case for the alkyl hydroperoxides in reaction 4, the enthalpies of the oxy-gen/hydrocarbon double exchange reaction 8 for dialkyl peroxides are different depending on the classification of the carbon bonded to oxygen. For R = Me, Et and f-Bu, the liquid phase values are —4, 24.6 and 52.7 kJmoR, respectively, and the gas phase values are 0.1, 25.7 and 56.5 kJmoR, respectively. For the formal deoxygenation reaction 9, the enthalpies of reaction are virtually the same for dimethyl and diethyl peroxide in the gas phase, —58.5 0.6 kJ moR. This value is the same as the enthalpy of reaction of diethyl peroxide in the liquid phase, —56.0 kJ moR (there is no directly determined liquid phase enthalpy of formation of dimethyl ether). Because of steric strain in the di-ferf-butyl ether, the enthalpy of reaction is much less negative, but still exothermic, —17.7 kJmol (Iq) and —19.6 kJmol (g). 

A similar reaction of 1,3-dimethyl ether p-t-Bu-calix[4]arene, abbreviated as (H2L), with Et2Zn affords a monomeric compound (EtZn)2(L) (169) with a less complex structure (Figure 84) °. The zinc atoms in this compound form a flat Zn—O—Zn—O arrangement together with the phenolate oxygen atoms. To each zinc atom one ethyl group is bonded, and tetrahedral coordination is reached by the additional coordination of one methoxy group. 

Olah and Bukala404 have developed a method for the oxidative carboxylation of methyl halides with CO and copper oxides or Cu and oxygen over SbF5-graphite [Eq. (5.156)]. Time-dependence studies indicated that the three products—methyl acetate, dimethyl ether, and methyl fluoride—were formed in parallel reactions. The reactivity of methyl halides shows the decreasing order MeBr > MeCl > MeF. 

Schoneich C, Dillinger U, von Bruchhausen F, Asmus K-D (1992) Oxidation of polyunsaturated fatty adds and lipids through thiyl and sulfonyl radicals reaction kinetics, and influence of oxygen and structure of thiyl radicals. Arch Biochem Biophys 292 456-467 Schuchmann H-P, von Sonntag C (1981) Photolysis at 185 nm of dimethyl ether in agueous solution Involvement of the hydroxymethyl radical. J Photochem 16 289-295 Schuchmann H-P, von Sonntag C (1997) Fleteroatom peroxyl radicals. In Alfassi ZB (ed) Peroxyl radicals. Wiley, Chichester, pp 439-455... 

The initial dehydration reaction is sufficiently fast to form an equilibrium mixture of methanol, dimethyl ether, and water. These oxygenates dehydrate further to give light olefins. They in turn polymerize and cyclize to form a variety of paraffins, aromatics, and cycloparaffins. The above reaction path is illustrated further by Figure 3 in terms of product selectivity measured in an isothermal laboratory reactor over a wide range of space velocities. ( 3) The rate limiting step is the conversion of oxygenates to olefins, a reaction step that appears to be autocatalytic. In the absence of olefins, this rate is slow but it is accelerated as the concentration of olefins increases. 

Raw stock for the direct synthesis of methylchlorosilanes, methylchlo-ride, has such impurities as moisture, methyl alcohol, oxygen, sulfur dioxide, methylenechloride, dimethyl ether, carbon oxide and dioxide, etc. Most of them negatively affect the synthesis of methylchlorosilanes harmful impurities are chemisorbed on the active centres of contact mass and foul the copper catalyst, which naturally inhibits the reaction of methyl-chloride with contact mass. A similar situation is observed in the direct synthesis of ethylchlorosilanes. 

The ideal (Oil -faceted surface contains exclusively five-coordinate titanium cations, so a bimolecular disproportionation reaction (see reaction (23)) to produce the ether product is precluded. Although the sputtered surface contains low-coordinate titanium cations and ample oxygen vacancies, the formation of dimethyl ether is exclusive to the (114 -faceted surface. In fact, the defect density drives all of the methoxides to fill those oxygen vacancies, and the resulting carbon is deposited on the surface, only to be burned off as CO, as illustrated in reaction (24) [74]. 

A number of oxygen and sulphur compounds are sufficiently powerful electron-pair donors to form borine adducts by reaction with diborane. Of these the unstable solid dimethyl ether borine, Me20+.BH3, used in the purification of diborane, is well known. 

The movement of electrons in Lewis acid-base reactions can be seen clearly with electrostatic potential maps. In the reaction of boron trifluoride with dimethyl ether, for instance, the ether oxygen atom becomes more positive and the boron becomes more negative as electron density is transferred and the B-0 bond forms (Figure 2.6). 

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