Dimethylether Carbonylation

For ethers of higher alcohols, activity comparable to that of dimethylether is observed with the [Ru(00) 13] catalysts, where simple carbonylation is favoured over homologation ( 1). ... 

Cl gHi 4Fe20y, Hexacarbonyl (m ( (1,2,3-tj 3,4,5-t )-2-(1,1-dimethyleth-yl)-4-methy1-1-0x0-2,3-pentadiene-1,5-diyl))diiron, 42B, 662 Cl gHi 4Mn203, /x Allene-iLi-carbonyl-bis(carbonyl-72 -cyclopentadienyl-manganese), 46B, 843... 

Alcohol Homologation Solvent and promoter effects on the cobalt carbonyl catalysed methanol homologation have been studied under synthesis gas pressure.The main product in a methanol/hydrocarbon two-phase system is 1,1-dimethoxyethane (ca. 70 selectivity).Using similar iodide promoted cobalt catalysts, R2C 0Me)2 and dimethylcarbonate are converted to acetaldehyde with up to 87 selectivity.Ruthenium in the presence of Co, 12 and dppe improves the ethanol selectivity in the homologation of dimethylether. Best results are achieved in inert solvents with high dielectric constants, e.g. sulfolane (e = 44), and with BF3 as activator. 

All these reactions take place in the organic part of the catalytic cycle and leave the organometallic cycle unchanged. The net result is the carbonylation of dimethylether to acetic anhydride. Under certain engineering and commercial requirements, manufacturing acetic anhydride from dimethylether rather than methyl acetate is more advantageous. 

Explain the following observations (a) Ru(CO) Ij and Pt(CO)jIj act as promoters in Ir-catalyzed carbonylation but not in Rh-catalyzed carbonylation of methanol (b) in the concentration of LP ([LP]) versus initial rate plots of methyl acetate carbonylation, at low [Li ] the initial rate increases and then at higher [LP] it levels off (c) acetaldehyde and propionic acid are side products of Rh- and Ir-catalyzed carbonylations (d) instead of methyl acetate, dimethylether can also be carbonylated to give acetic anhydride (e) in the Pd-catalyzed carbonylation of methyl acetylene, the amount of CHjCH=CH(C02Me) formed is very httle (f) Co-catalyzed carbonylation of benzyl chloride to phenyl acetic acid requires a phase-transfer catalyst (g) a neutral catalytic intermediate may be involved in Rh-catalyzed WGS reaction (h) complexes of the general formula A X where A is a Lewis acid are effective catalysts for polymerizing epoxides with CO (i) reaction... 

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