Ethylene carbonyl oxides

FIGURE 17. Transition structures for the epoxidation of ethylene by carbonyl oxide [A(E- -ZPVE) = 10.2 kcalmoU ] and dimethylcarbonyl oxide [A(E-I-ZPVE) = 10.3 kcalmol" ] optimized at the B3LYP/6-311- -G(d,p) level of theory. Bond lengths given in brackets are at the MP2/6-31G(d) level, and the corresponding barriers are 14.8 and 12.9 kcalmoU ... 

Ethylene epoxidation with unsubstituted carbonyl oxide is ca 5 kcalmol" more exothermic than with dimethylcarbonyl oxide, yielding an even earlier transition state. 

In summary, transition structures with dioxirane and dimethyldioxirane are unsymmet-rical at the MP2/6-31G level, but are symmetrical at the QCISD/6-31G and B3LYP/6-31G levels. The transition states for oxidation of ethylene by carbonyl oxides do not suffer from the same difficulties as those for dioxirane and peroxyforaiic acid. Even at the MP2/6-31G level, they are symmetrical (Figure 17). The barriers at the MP2 and MP4 levels are similar and solvent has relatively little effect. The calculated barriers agree well with experiment . In a similar fashion, the oxidation of ethylene by peroxyformic acid has been studied at the MP2/6-31G, MP4/6-31G, QCISD/6-31G and CCSD(T)/6-31G and B3LYP levels of theory. The MP2/6-31G level of theory calculations lead to an unsymmetrical transition structure for peracid epoxidation that, as noted above, is an artifact of the method. However, QCISD/6-31G and B3LYP/6-31G calculations both result in symmetrical transition structures with essentially equal C—O bonds. 

Oxidation with Palladium in the Homogeneous Phase. The most thoroughly studied reaction concerning the transformation of alkenes to carbonyl compounds is their oxidation catalyzed by palladium in homogeneous aqueous media.243 244 494-503 As a rule, ethylene is oxidized to acetaldehyde, and terminal alkenes are converted to methyl ketones.504 505... 

Organic constituents that may be found in ppb levels in WP/F smoke include methane, ethylene, carbonyl sulfide, acetylene, 1,4-dicyanobenzene, 1,3-dicyanobenzene, 1,2-dicyanobenzene, acetonitrile, and acrylonitrile (Tolle et al. 1988). Since white phosphorus contains boron, silicon, calcium, aluminum, iron, and arsenic in excess of 10 ppm as impurities (Berkowitz et al. 1981), WP/F smoke also contains these elements and possibly their oxidation products. The physical properties of a few major compounds that may be important for determining the fate of WP/F smoke in the environment are given in Table 3-3. 

The complex 100 is calculated to be more stable than the separated aldehyde and carbonyl oxide by 9 kcal mol-1 and the formation of complex 100 from ethylene and ozone is endothermic by only 3.1 kcal mol-1 <1991CPL(187) 491 >. Cycloaddition then leads to the secondary ozonide 101 (1,2,4-trioxolane). subsequent study of the stereochemistry of ozonation reactions using the AMI method provides further support for the modified Criegee mechanism C1997JOC2757, CHEC-III(6.06.2)193>. 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Stannyl anions with a highly coordinated tin center are also known. A hydridostannyl anion in the shape of a trigonal bipyramid in which two iodine atoms occupy the apical positions was obtained by oxidative addition of lithium iodide to the corresponding tin hydride (equation 58) . It was characterized by Sn NMR. Since apical iodines are more nucleophilic than the hydrogen, in its reactivity with a-ethylenic carbonyl compounds, attack by iodine precedes reduction by hydrogen, achieving regioselective 1,4 reductions. 

The processes for the manufacture of acetic anhydride have included, initially, the distillation of wood pulp, which was followed by the ketene route from acetic acid or acetone and finally the ethylene based oxidation of acetaldehyde. The carbonylation of CH3OAC to acetic anhydride has in part replaced anhydride capacity from the more expensive processes. 

Jn a potentially far reaching application for melt catalysis by the transition metals, we at Texaco have demonstrated the synthesis of a range of commodity chemicals and fuels directly from CO/H2 via the use of ruthenium-containing molten salt catalysis. Products include ethylene glycol, Ci-C4 alcohols, acetic acid, acetate esters, C2+ olefins and vicinal glycol esters. In its simplest form, this new class of melt catalyst comprises one or more ruthenium sources, e.g. ruthenium carbonyls, oxides, complexes, etc. dispersed in a low-melting (m.p. <150 C) quaternary phosphonium or ammonium salt (e.g. tetrabutylphos-phonium bromide). The key components are selected such that ... 

Carbonylation, oxidative -, P-acoxycarboxylic acid anhydrides from ethylene derivs. 44, 640 Carbonylation, phase transfer catalyzed 44, 807... 

Palladous chloride j cupric chloride j sodium chloride p-Acoxycarboxylic acid anhydrides from ethylene derivs. Oxidative carbonylation... 

The carbonylative oxidation of alkenes catalyzed by palladium catalysts has been extensively studied owing to its industrial importance. The conversion of ethylene to acrylic acid has been developed into a commercial process by Union Oil (Scheme 10). The reaction is performed in a mixed solvent of acetic acid and acetic anhydride in the presence of a Wacker catalyst under high pressure of ethylene. 

The carbonylative oxidation of propene under the same conditions affords crotonic acid as the major product rather than the more valuable methacryhc acid (Scheme 12). When the reaction of ethylene or terminal alkenes is carried out in alcoholic solvents instead of AcOH, dialkyl succinates and /3-alkoxy esters become the major products... 

On the other hand, new processes are being researched, such as i) the named Alpha process via ethylene carbonylation to methyl propionate, very similar to the aforementioned BASF route ii) the one-step method of propyne catal3dic carbonylation and iii) direct oxidation of isobutane to methacrolein or methacrylic acid. The use of isobutyraldehyde and isobutyric acid as feedstocks has also been explored. Among all these methods, the one employing the alkane in a one-step reaction to form methacrylic acid is the most simple and interesting process from both... 

The initial reaction of O3 and alkenes are known to be the formation of carbonyl compounds and carbonyl oxide via primary ozonide formed by cyclic addition of O3 to double bond. In the case of ethylene, the reaction formula can be represented as. 

The reaction of lithiated cumulenic ethers with ethylene oxide, trimethyl-chlorosilane and carbonyl compounds shows the same regiosnecificity as does the alkylation. 

Oxidative Carbonylation of Ethylene—Elimination of Alcohol from p-Alkoxypropionates. Spectacular progress in the 1970s led to the rapid development of organotransition-metal chemistry, particularly to catalyze olefin reactions (93,94). A number of patents have been issued (28,95—97) for the oxidative carbonylation of ethylene to provide acryUc acid and esters. The procedure is based on the palladium catalyzed carbonylation of ethylene in the Hquid phase at temperatures of 50—200°C. Esters are formed when alcohols are included. Anhydrous conditions are desirable to minimize the formation of by-products including acetaldehyde and carbon dioxide (see Acetaldehyde). 

The elimination of alcohol from P-alkoxypropionates can also be carried out by passing the alkyl P-alkoxypropionate at 200—400°C over metal phosphates, sihcates, metal oxide catalysts (99), or base-treated zeoHtes (98). In addition to the route via oxidative carbonylation of ethylene, alkyl P-alkoxypropionates can be prepared by reaction of dialkoxy methane and ketene (100). 

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