Dimethyl ether 498 Subject

The mechanism of the conversion of methanol to hydrocarbons has been the subject of substantial studies 450-455 Despite the intensive research, however, many details of this very complex transformation remain unsolved. It now appears generally accepted that methanol undergoes a preliminary Brpnsted acid-catalyzed dehydration step and that dimethyl ether, or an equilibrium mixture of dimethyl ether and methanol, acts as the precursor to hydrocarbon formation 433... 

The photodecomposition of oxiran and alkyloxirans both in the gas phase and in solution has been extensively investigated. Processes arising by carbon-oxygen bond homolysis and hydrogen abstraction have been reported, and the subject has been reviewed in detail elsewhere.48 The most recent studies include the photoaddition of methanol to alicyclic epoxides, a process that appears to be promoted by acid,49 and the interesting if unusual photochemically induced conversion of the epoxyalcohol (56) to sugiresinol dimethyl ether (57).50... 

The selectivity of the Complex Formation is a very interesting subject, y - Cyclodextrin, (y - CD) has been found to form inclusion complexes with poly (methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), and poly(n- propyl vinyl ether) (PnPVE) of various molecular weights to give stoichiometric compounds in crystalline states. However, a- cyclodextrin (a - CD) and (3 - Cyclodextrin ((3- CD) did not form complexes with poly (alkyl vinyl ether)s of any molecular weight, y -CD did not form complexes with the low molecular weight analogs, such as diethyl ether and trimethylene glycol dimethyl ether. 

Subsequently, glaucine was subjected to Hofmann degradation (14), and the methiodide (m.p. 222°) as well as the tetramethoxyvinylphenan-threne (m.p. 142°) were shown to be identical with the same derivatives prepared from boldine dimethyl ether (15). The corresponding tetra-methoxyphenanthrene-8-carboxylic acid melts at 213° (15). 

Methanol decomposes to formaldehyde when it is subject to the ultraviolet radiation contained in the sun light, even extraordinarily slowly. The direct oxidation on suitable catalysts and at tempoatures of 650 to 1000°C yields formaldehyde. Dimethyl ether is produced from methanol by dehydration. 

The reaction shown is an oversimplification and items such as shifting the equilibrium toward methanol, catalyst poisoning, and pressure/temperature tradeoffs need to be considered and are the subject of a text [3]. Methanol has many uses as a solvent and is the major component of windshield washer fluid. However, most methanol is converted to other commodity chemicals such as acetic acid, formaldehyde, or dimethyl terephthalate. It can also be used directly as a fuel additive, as a component in the synthesis of biodiesel or converted to dimethyl ether or methyl-t-butyl ether (MTBE), two fuel additives. 

L-dihydroxy-succinic acid (L(dexiro)-tartaric acid, CXIII). This result establishes the position of the double bond between C4 and C5 and demonstrates that C4 carries only one hydrogen atom while C5 has attached to it the enolic hydroxyl group. Treatment of the enol CXI with ethereal diazomethane gives 5-methyl-A4-D-glucosaccharo-3,6-lactone methyl ester (CXIY) which upon further methylation with silver oxide and methyl iodide yields 2,5-dimethyl-A4-D-glucosaccharo-3,6-lactone methyl ester (CXV). When the latter is subjected to ozonolysis there is formed oxalic acid and 3-methyl-L-threuronic acid (CXVI). Oxidation of this aldehydic acid (CXYI) with bromine gives rise to a monomethyl derivative (CXVII) of L-ilireo-dihydroxy-succinic acid. 

---