Isomerization of methyl formate

The production of methyl formate by carbonylation of methanol with basic catalysts [134] can be used to separate carbon monoxide from by-product synthesis gas streams, e.g., steel-mill off-gases [135], to generate clean sources of CO for production of acetic acid by methyl formate isomerization. Therefore methyl formate could be produced near cheap CO sources and then transported to an appropriate site for conversion to acetic acid. This route to acetic acid is potentially competitive with a classic grass-roots methanol carbonylation process. Though the process has not been commercialized, numerous companies have patented the isomerization of methyl formate [136]. 

Isomerization of methyl formate to acetic acid is a well-known reports in the patent literature date back to 1929. With a Co-iodide catalyst the reaction is carried out at 160° and 10.5 MPa CO . The selectivity to acetic acid is >95%. The best reported productivities are obtained with a Rh-Lil catalyst. In this case, the reaction is carried out at 180°C and 2.75 MPa with 99% conversion and near quantitative yield of acetic acid. The mechanism of the reaction involves initial cleavage of methyl formate by Lil. CH3I, obtained in the cleavage reaction, is carbonylated to acetyl iodide via the same catalytic chemistry observed in CH3OH carbonylation. The key to making acetic acid is that the mixed anhydride CHjCfOlOCfOlH is unstable and thermally decomposes to acetic acid and CO at the reaction conditions. 

Ir(Cl)3] catalyzes the isomerization of methyl formate at 473-508 K/33-250 bar CO in the presence of an Mel promoter. The major product is acetic acid, with methyl acetate as a byproduct. The synthesis of PhNCO via carbonylation of PhN02 at 398 K under 80 atm CO pressure can be catalyzed by [ (COjjCPPhjjj] . ... 

In a carboxylic acid solvent, [Ir(cod)Cl]2 with a Mel promotor effects the isomerization of methyl formate to acetic acid. Kinetic and chemical studies indicate that the reaction proceeds in the carboxylic acid by transesterification to give formic acid which then reacts with iridium (Scheme 9). " ... 

An interesting reaction of methyl formate is its isomerization to give acetic acid. Based on patent literature, a number of companies have recently reinvestigated this isomerization which has been known for over 30 years ( ). It is unlikely that it can compete with the Monsanto process however, since it doesn t need pure CO and may be operable at milder reaction conditions, some potential may be seen. Combining isomerization to acetic acid and decarbonylation to methanol and CO, could provide a direct synthesis for acetic anhydride starting directly from methyl formate (Equation 13). 

Effect of /3-cyclodc trin on cis trans isomerization of azobenzenes was studied by Sanchez and de Rossi [26], It was found that the cis-trans thermal isomerization of / -Mcthvl Red, o-Methyl Red and Methyl Orange is inhibited by fi-CD at constant pH. The isomerization rate decreases 4, 8, and 1.67 times, respectively, in a solution containing 0.01 M /J-CD. This effect was attributed to the formation of inclusion complexes hindering rotation of the -N=N- bond. Isomerization of Methyl Yellow and naphthalene-l-azo-[4 -(dimethylamino)benzene] requiring mixed organic-aqueous... 

The formation of benzene by the dehydroaromatization coupled with isomerization of methyl cyclopentane also increases octane from 76 to 106. 

The ready hydrogenation and isomerization of methyl oleate and palmitoleate with Fe(CO)s confirm the results of Ogata and Misono (18) with monounsaturated aliphatic compounds. In the isomerization of monoolefins Manuel (15) suggested the occurrence of equilibria involving either 7r-olefin HFe(CO)3 and a-alkyl Fe(CO)3 complexes, or TT-olefin Fe(CO)3 and 7r-allyl HFe(CO)3 complexes. The formation of olefin-iron tetracarbonyl complexes has been reported (19). The reaction of butadiene and Fe2(CO)9 has been observed to lead to the formation of butadiene-Fe(CO)4 and butadiene-[Fe(CO)4]2 complexes in which one or both double bonds are pi-bonded to the iron (16). A mechanism involving both monoene-Fe(CO)4 (I) and allyl-HFe(CO)3 complexes (II) is postulated for the isomerization of methyl oleate (Scheme II) and for its homogeneous hydrogenation. 

Although direct measurement of reactant temperatures have enabled more quantitative assessment of such reactions, precise tests of thermal explosion theory require a reaction for which the mechanism and Arrhenius parameters are sufficiently well established to give accurate estimates of rates under explosive conditions. Typically the reaction rates involved will be around ten times those determined by static kinetic methods. In addition the thermal conductivity of each gas mixture used and the stoicheiometry and heat of reaction must be known. Pritchard and Tyler suggest the thermal isomerization of methyl isocyanide as a suitable candidate. They report temperature-time records for diluted mixtures in which temperature excesses of 70—80 K occur without explosion. However, the roll-call of missing data—improved heats of formation, isothermal kinetic data at higher temperatures, thermal conductivity measurements up to 670 K, and the recognition and elucidation of side reactions (if any) indicate the extent of further investigations necessary if their proposal is to be fully realized. 

As a method for the preparation of alkenes, a weakness in the acid-catalyzed dehydration of alcohols is that the initially formed alkene (or mixture of alkenes) sometimes isomerizes under the conditions of its formation. Write a stepwise mechanism showing how 2-methyl-1-butene might isomerize to 2-methyl-2-butene in the presence of sulfuric acid. 

The formation of an enamine from an a,a-disubstituted cyclopentanone and its reaction with methyl acrylate was used in a synthesis of clovene (JOS). In a synthetic route to aspidospermine, a cyclic enamine reacted with methyl acrylate to form an imonium salt, which regenerated a new cyclic enamine and allowed a subsequent internal enamine acylation reaction (309,310). The required cyclic enamine could not be obtained in this instance by base isomerization of the allylic amine precursor, but was obtained by mercuric acetate oxidation of its reduction product. Condensation of a dihydronaphthalene carboxylic ester with an enamine has also been reported (311). 

An interesting kinetic study was carried out under pseudo-first-order conditions for the base hydrolysis of the three isomeric N-methyl-cyanopyridinium salts, a reaction that leads partly to CN replacement and partly to the formation of a carboxamido derivative. ... 

Dipolar additions of diazomethane to acetylenes under mild conditions are restricted to monosubstituted acetylenes thus the formation of pyrazole derivatives 1 (1,3-dipolar addition, C=C isomerization, then methylation) confirms the existence of a terminal acetylene in caryoynencins (87TL3981) (Scheme 5). 

The most radiation-stable poly(olefin sulfone) is polyethylene sulfone) and the most radiation-sensitive is poly(cyclohexene sulfone). In the case of poly(3-methyl-l-butene sulfone) there is very much isomerization of the olefin formed by radiolysis and only 58.5% of the olefin formed is 3-methyl-l-butene. The main isomerization product is 2-methyl-2-butene (37.3% of the olefin). Similar isomerization, though to a smaller extent, occurs in poly(l-butene sulfone) where about 10% of 2-butene is formed. The formation of the olefin isomer may occur partly by radiation-induced isomerization of the initial olefin, but studies with added scavengers73 do not support this as the major source of the isomers. The presence of a cation scavenger, triethylamine, eliminates the formation of the isomer of the parent olefin in both cases of poly(l-butene sulfone) and poly(3-methyl-1-butene sulfone)73 indicating that the isomerization of the olefin occurred mainly by a cationic mechanism, as suggested previously72. 

Intermediate species concentrations in fuel-rich flames (C/O = 0.5) of the two isomeric esters methyl acetate (left) and ethyl formate (right) burnt under identical conditions mole fraction, h height species named on the left side of each graph correspond to left y-axes, species on the right to right y-axes. 

More recently, a new mode of cis-trans isomerization of a disilene has been suggested for the extremely hindered disilene 27. As will be detailed in Section VIII. B, 27 undergoes thermal dissociation into the corresponding silylenes. Monitoring the thermolysis of (Z)-27 at 50°C by H and 29Si NMR reveals a competitive formation of the isomerized ( >27 and benzosilacyclobutene 37, which is most likely formed by intramolecular insertion of silylene 36 into the C—H bond of the o-bis(trimethylsilyl)-methyl group (Scheme 3).22,59 This suggests the possible occurrence of cis-trans isomerization via a dissociation-association mechanism. 

Yang has observed that cis-trans isomerization of 3-methyl-2-pentenes is accompanied by oxetane formation and concluded that intermediates such as (22) are common to both isomerization and oxetane formation/825 Deuterium isotope effects are also consistent with the involvement of this type of intermediate/83,845 ... 

DHN. Apparently DHN both thermally dehyrogenates to naphthalene and disproportionates to Tetralin and naphthalene. In all of the runs, there was a sizable amount of hydrogen released when the reactors were opened. When DHN was heated at 450°C for either 15 or 180 minutes, the ratio of naphthalene to etralin was 1.8. Increased methyl indan formation occurred with time. With the introduction of dibenzyl, the anticipated [2] increased isomerization of T etralin to methyl indan occurred. These results suggest that the rearrangement of hydroaromatics does not proceed through the dihydro-... 

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