Ethers dimethyl

Dimethyl ether is used as a propellant in aerosols. It is also a solvent, a fuel used in welding, and a refrigerant. In high concentrations, it has an anesthetic effect. 

SOME PHYSICAL AND THERMODYNAMIC PROPERTIES OF DIMETHYL ETHER AT VARIOUS TEMPERATURES 

Tem- perature Vapor pressure atm. Density Dielec- trie constant Heat of vapori-ution kcal/kg Enthalpy Entropy  

Solubilil) of Methyl Ether at Vhrioiis Pressures Temperature 25K  

C artHMi ictraditorMc Asxionc Benzene Chlorohenzene Mclhyt accialc  

As for the diethyl ether mentioned in Chap. 3, the acid-base function designated as n-C5HiiC02H---0(CH3)2 and especially CI3CCH2OH---0(013)2 is clearly discernible but n -octanol and dimethylf ormamide are not especially accommodating. 

As with sufur dioxide, methyl chloride, and hydrogen sulfide, so with dimethyl ether there is no systematic correlation between Xmc20 (or Me2o) on the one hand, and dipole moment or dielectric constant of S, on the other. 

Looking at Fig. 113, it can be visualized that at —20°C the whole of each line could be drawn on the existing scale of that diagram. The lines would be less steep and would tend to cluster by the stage where the horizontal at 1 atm was reached. At 

300 mm Hg, for example, the separation of the lines would still be quite distinct. At —30° the systems would be conventionally called liquid-liquid ones (when S was still liquid), but the pattern would be essentially similar. 

The flexibility of DME, considering both source and application, makes it a strong case in a long-term scenario. 

One major advantage of DME use is that it can be stored as a high-density liquid phase at modest pressures (around 5 atm) and delivered as a gas-phase fuel in a pumpless operation. Therefore, the use of DME can potentially combine the advantages of easy fuel delivery of pressurized hydrogen and the high energy density storage of liquid fuel. In addition, DME is less toxic than methanol. 

Currently, the major application of DME is as an aerosol propellant, for example in hairsprays and paintsprays, where it has replaced the formerly used ozone-destroying chlorofluorocarbons (CFCs). 

DME can be produced from any carbonaceous material, such as natural gas, coal, crude oil and regenerable resources such as biomass [208-212]. 

Eundamental research on DME synthesis from renewable sources is ongoing. In Sweden, for example, Chemrec developed a process for producing DME through 

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CH3.O-CH2.CH2-O.CH2-CHj-O.CH3. Dimethyl ether of diethylene glycol. A colour-less liquid b.p. 160 C. Typical ether, useful as a high-temperature solvent. 

Brodbelt J, Liou C-C and Donovan T 1991 Selective adduct formation by dimethyl ether chemical ionization is a quadrupole ion trap mass spectrometer and a conventional ion source Ana/. Chem. 63 1205-9... 

Other compounds containing lone pairs of electrons readily form co-ordinate links and in each case a change in spatial configuration accompanies the bond formation. The oxygen atom in dimethyl ether, CHj—O—CHj, has two lone pairs of electrons and is able to donate one pair to, for example, boron trichloride ... 

This compound, which contains atoms arranged tetrahedrally around the boron atom, can readily be isolated from a mixture of dimethyl ether and boron trichloride. On occasions a chlorine atom, in spite of its high election affinity, will donate an electron pair, an example being found in the dimerisation of gaseous monomeric aluminium chloride to give the more stable Al2Clg in which each aluminium has a tetrahedral configuration ... 

Di-alkyl ethers of ethylene glycol, ROCHjCHjOR. The dimethyl ether, b.p. 85°/760 mm., is miscible with water, is a good solvent for organic compounds, and is an excellent inert reaction medium. The diethyl ether (diethyl cdloaolve), b.p. 121-57760 mm., is partially miscible with water (21 per cent, at 20°). 

Similar activation takes place in the carbonylation of dimethyl ether to methyl acetate in superacidic solution. Whereas acetic acid and acetates are made nearly exclusively using Wilkinson s rhodium catalyst, a sensitive system necessitating carefully controlled conditions and use of large amounts of the expensive rhodium triphenylphosphine complex, ready superacidic carbonylation of dimethyl ether has significant advantages. 

A new approach we found is based on the initial bromination of methane to methyl bromide, which can be effected with good selectivity, although still in relatively low yields. Methyl bromide is easily separated from exeess methane, whieh is readily recyeled. Hydrolysis of methyl bromide to methyl alcohol and its dehydration to dimethyl ether are readily achieved. Importantly, HBr formed as by produet ean be oxidatively reeycled into bromine, making the overall proeess cat-alytie in bromine. 

The chemical recycling of carbon dioxide into usable fuels provides a renewable carbon base to supplement and eventually replace our diminishing natural hydrocarbon resources. Methanol (or dimethyl ether), as discussed, can be readily converted into ethylene or, by further reaction, into propylene. 

Tms (trimethylsilyl) = MejSi triglyme triethylene glycol dimethyl ether =... 

The constitutional isomer of ethanol dimethyl ether (CH3OCH3) IS a gas at room temperature Suggest an explanation for this observation I... 

Diglyme shown above the arrow in the equation is the solvent in this example Diglyme is an acronym for d/ethylene g/ycol dimethyl ether and its structure is CH3OCH2CH2OCH2CH2OCH3... 

Use Learning By Modeling to make models of water methanol dimethyl ether and di tert butyl ether Mini mize their geometries and examine what happens to the C—O—C bond angle Compare the C—O bond dis tances in dimethyl ether and di tert butyl ether... 

Make a molecular model of dimethyl sulfide How does its bond angle at sulfur compare with the C—O—C bond angle in dimethyl ether"d... 

View molecular models of dimethyl ether and ethylene oxide on Learning By Modeling Which one has the greater dipole moment Do the calculated dipole moments bear any relation ship to the observed boiling points (ethylene oxide +10°C dimethyl ether —25°C) d... 

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