Oxo syntheses

Oxo synthesis, or more formally hydroformylation, is an olefin/CO coupling reaction which in the presence of hydrogen leads to the next higher aldehyde. The process was discovered in 1938 by Otto Roelen at Ruhrchemie, where it was first commercialized [4]. This reaction is the most important industrial homogeneous catalysis in terms of both scale and value. The most important olefin starting material is propene, which is mainly converted to 1-butanol and 2-ethylhexanol via the initial product butyraldehyde (Eq. 3-1). 

The most important location for this reaction is Germany, with the plants of Hoechst (Ruhrchemie works in Oberhausen) and BASF in Ludwigshafen. Approximately 50 % of world capacity is located in Europe and about 30 % in the USA. Numerous industrial variants of 0x0 synthesis are known. Cobalt and rhodium catalysts are used, the latter now being preferred [3]. 

The original catalyst was [Co2(CO)8], which was modified with phosphines to increase the yield of the industrially more important linear aldehydes. A breakthrough was achieved in 1976 at Union Carbide with the introduction of rhodium catalysts such as [HRh(CO)(PPh3)3]. The rhodium-catalyzed process operates at ca. 100°C and 10-25 bar and gives a high ratio of linear to branched products. 

The low pressure allows the synthesis gas to be used directly imder its normal production conditions, so that investments for compressors and high-pressure reactors can be saved. However, the economic advantages are strongly dependent on the lifetime of the expensive catalysts, and loss-free catalyst recovery is of crucial importance [14]. 

The mechanisms of hydroformylation with rhodium and cobalt catalysts have been studied in detail and are very similar. We have already learnt that for cobalt the active catalyst precursor is [HCo(CO)4] in the case of the modified rhodium catalyst it is the complex [HRh(CO)(PPh3)3]. 

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Oxo Synthesis. Ad of the synthesis gas reactions discussed to this point are heterogeneous catalytic reactions. The oxo process (qv) is an example of an industriady important class of reactions cataly2ed by homogeneous metal complexes. In the oxo reaction, carbon monoxide and hydrogen add to an olefin to produce an aldehyde with one more carbon atom than the original olefin, eg, for propjiene ... 

Aliphatic Aldehyde Syntheses. Friedel-Crafts-type aUphatic aldehyde syntheses are considerably rarer than those of aromatic aldehydes. However, the hydroformylation reaction of olefins (185) and the related oxo synthesis are effected by strong acid catalysts, eg, tetracarbonylhydrocobalt, HCo(CO)4 (see Oxo process). 

With the exception of acetic, acryUc, and benzoic all other acids in Table 1 are primarily produced using oxo chemistry (see Oxo process). Propionic acid is made by the Hquid-phase oxidation of propionaldehyde, which in turn is made by appHcation of the oxo synthesis to ethylene. Propionic acid can also be made by oxidation of propane or by hydrocarboxylation of ethylene with CO and presence of a rhodium (2) or iridium (3) catalyst. 

Butyric acid is made by air-oxidation of butyraldehyde, which is obtained by appHcation of the oxo synthesis to propylene. Isobutyric acid is made from isobutyraldehyde, a significant product in the synthesis of butyraldehyde (see Butyraldehydes). Butyraldehyde is also used to make 2-ethylhexanoic acid. 

Oxo Synthesis Products, Earbwerke Hoechst AG, Erankfurt, Germany, 1971. 

Carbazole, 2-hydroxy-reactions with citral, 4, 235 Carbazole, 2-hydroxy-9-methyl-synthesis, 4, 294 Carbazole, N-hydroxymethyl-as metabolite of carbazole, 1, 230 Carbazole, N-isopropyl-PE spectroscopy, 4, 190 Carbazole, A7-methyl- N NMR, 4, 175 X-ray spectroscopy, 4, 163 Carbazole, 1-nitro-synthesis, 4, 282 Carbazole, tetrahydro-dehydrogenation, 4, 282, 312 synthesis, 4, 107, 337, 353 Carbazole, 1,2,3,4-tetrahydro-reduction, 4, 255, 256 synthesis, 4, 312, 325, 352 Carbazole, 1,2,3,4-tetrahydro-1 -oxo-synthesis, 4, 337 Carbazole, 9-trifluoroacetyl-synthesis, 4, 218 Carbazole, vinyl-polymers, 1, 275, 301 Carbazole, 9-vinyl-copolymer... 

Coumarin, 5,6,7,8-tetrahydro-5-oxo-synthesis, 3, 790 Coumarin, 4-trifluoromethyl-synthesis, 3, 800... 

H-lmidazo[4,5-g]pteridin-2-one, 8-amino-6-phenyl-2,3-dihydro-synthesis, 3, 304 Imidazopurines, 5, 564 Imidazopurines, oxo-synthesis, 5, 565... 

A -0-2-Isocephem-4-carboxylic acid, 1-P-phenoxyacetamido-3-methyl-1 -oxo-synthesis, 1, 430 Isochroman, 1,3-diphenyl-synthesis, 3, 787, 788 Isochroman, 3,4-diphenyI-conformation, 3, 631 Isochroman, 2-methyl-synthesis, 3, 788 Isochroman, 3-phenyl-synthesis, 3, 788 Isochroman, (-)-)-(i )-3-phenyI-stereoselective synthesis, 3, 789 Isochroman-4-carboxylic acid, l-oxo-3-phenyl-synthesis, 3, 860 Isochroman-I,3-diones, 4-acyI-synthesis, 3, 831 Isochromanols dehydration, 3, 767 isochroman synthesis from, 3, 789 Isochroman-1-one, 3-aryl-synthesis, 3, 858, 860... 

Oxadiazolo[3,4-c]pyridine, 3(l)-oxo-synthesis from 4-azido-3-nitropyridines, 6, 730... 

Pteridine-7-carboxamide, JV-methyl-6-oxo-synthesis, 3, 310 Pteridine-4-carboxamides properties, 3, 276... 

Pteridine-7-carboxylic acid, 6-oxo-synthesis, 3, 310 Pteridinecarboxylic acids structure, 3, 276-277 Pteridine-4-carboxylic acids ethyl ester hydrolysis, 3, 276 Pteridine-6-carboxylic acids properties, 3, 277 reactions, 3, 304 Pteridine-7-carboxylic acids properties, 3, 277 reactions, 3, 304 Pteridine-6,7-dicarboxylic acid properties, 3, 277 Pteridine-2,4-dione, 7-hydroxy-tautomerism, 3, 271... 

Purine, 2-amino-1 -methyI-6-thioxo-1,6-dihydro-synthesis, 5, 596 Purine, 8-amino-2-oxo-synthesis, 5, 579 Purine, 8-amino-6-oxo-synthesis, 5, 579... 

Purine, 9-methyl-8-thioxo-7,8-dihydro-synthesis, 5, 578 Purine, 2-oxo-synthesis, 5, 587 UV spectra, 5, 517 Purine, 8-oxo-synthesis, 5, 576 UV spectra, 5, 517 Purine, 2-oxodihydro-alkylation, 5, 532 Purine, 2-oxo-2,3-dihydro-synthesis, 5, 596 Purine, 8-oxo-7,8-dihydro-synthesis, 5, 577, 582, 596 Purine, 6-oxo-2-thioxo-synthesis, 5, 574 Purine, 6-oxo-8-thioxo-synthesis, 5, 578 Purine, 6-phenacylthio-nucleosides dethiation, 5, 558 Purine, 8-phenyl-synthesis, 5, 575, 576 Purine, 8-phenyloxo-synthesis, 5, 576 Purine, 9-phenyl-8-thioxo-synthesis, 5, 578 Purine, 9-(2-propenyl)-synthesis, 5, 592 Purine, 8-(2-pyridyl)-synthesis, 5, 576 Purine, 8-(3-pyridyl)-synthesis, 5, 576... 

Pyrrolidine-3-carboxylic acid, 4-oxo-synthesis, 4, 518 Pyrrolidinediones polymerization, I, 271-272 Pyrrolidinediones, tetramethyl-... 

Thiophene, 3-nitro-4-(phenylsulfonyl)-cine substitution, 4, 817, 825 Thiophene, oxo-synthesis, 4, 125... 

Xanthene-2-carboxylic acid, 7-hydroxy-9-oxo-synthesis, 3, 837 Xanthenes... 

Synthesis gas is an important intermediate. The mixture of carbon monoxide and hydrogen is used for producing methanol. It is also used to synthesize a wide variety of hydrocarbons ranging from gases to naphtha to gas oil using Fischer Tropsch technology. This process may offer an alternative future route for obtaining olefins and chemicals. The hydroformylation reaction (Oxo synthesis) is based on the reaction of synthesis gas with olefins for the production of Oxo aldehydes and alcohols (Chapters 5, 7, and 8). 

Cornils, B., Hydroformylation, Oxo Synthesis, Roelen Reaction New Synthesis with Carbon Monoxide, Springer Verlag, Berlin, New York, 1980, pp. 1-224. 

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