Oxo-reaction

Cobalt has an odd number of electrons, and does not form a simple carbonyl in oxidation state 0. However, carbonyls of formulae Co2(CO)g, Co4(CO)i2 and CoJCO),6 are known reduction of these by an alkali metal dissolved in liquid ammonia (p. 126) gives the ion [Co(CO)4] ". Both Co2(CO)g and [Co(CO)4]" are important as catalysts for organic syntheses. In the so-called oxo reaction, where an alkene reacts with carbon monoxide and hydrogen, under pressure, to give an aldehyde, dicobalt octacarbonyl is used as catalyst ... 

Although the yields are not high, PdCU or Pd black catalyzes oxo reactions of alkenes with CO and H2 to give aldehydes[32]. 

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 ... 

Commercial Olefin Reactions. Some of the more common transformations involving a-olefins ia iadustrial processes iaclude the oxo reaction (hydroformylation), oligomerization and polymerization, alkylation reactions, hydrobromination, sulfation and sulfonation, and oxidation. 

The mechanism of the cobalt-cataly2ed oxo reaction has been studied extensively. The formation of a new C—C bond by the hydroformylation reaction proceeds through an organometaUic intermediate formed from cobalt hydrocarbonyl which is regenerated in the aldehyde-forrning stage. The mechanism (5,6) for the formation of propionaldehyde [123-38-6] from ethylene is illustrated in Figure 1. 

Fig. 1. Mechanism for the unmodified cobalt oxo reaction which produces propionaldehyde from ethylene.

Mechanism ofLP Oxo Rea.ction. The LP Oxo reaction proceeds through a number of rhodium complex equilibria analogous to those ia the Heck-Breslow mechanism described for the ligand-free cobalt process (see Fig. 1). 

Fig. 4. Mechanism for the TPP-modified rhodium-catalyzed oxo reaction of propylene to -butyraldehyde.

The basis of the high normal to isoaldehyde selectivity obtained ia the LP Oxo reaction is thought to be the anti-Markovnikov addition of olefin to HRhCOL2 to give the linear alkyl, Rh(CO)L2CH2CH2CH2CH2, the precursor of straight-chain aldehyde. Anti-Markovnikov addition is preferred ia this... 

Propane, 1-propanol, and heavy ends (the last are made by aldol condensation) are minor by-products of the hydroformylation step. A number of transition-metal carbonyls (qv), eg, Co, Fe, Ni, Rh, and Ir, have been used to cataly2e the oxo reaction, but cobalt and rhodium are the only economically practical choices. In the United States, Texas Eastman, Union Carbide, and Hoechst Celanese make 1-propanol by oxo technology (11). Texas Eastman, which had used conventional cobalt oxo technology with an HCo(CO)4 catalyst, switched to a phosphine-modified Rh catalyst ia 1989 (11) (see Oxo process). In Europe, 1-propanol is made by Hoechst AG and BASE AG (12). 

The principal commercial source of 1-butanol is -butyraldehyde [123-72-8] obtained from the Oxo reaction of propylene. A mixture of n- and isobutyraldehyde [78-84-2] is obtained in this process this mixture is either separated initially and the individual aldehyde isomers hydrogenated, or the mixture of isomeric aldehydes is hydrogenated direcdy and the n- and isobutyl alcohol product mix separated by distillation. Typically, the hydrogenation is carried out in the vapor phase over a heterogeneous catalyst. For example, passing a mixture of n- and isobutyraldehyde with 60 40 H2 N2 over a CuO—ZnO—NiO catalyst at 25—196°C and 0.7 MPa proceeds in 99.95% efficiency to the corresponding alcohols at 98.6% conversion (7,8) (see Butyraldehydes Oxo process). 

Historically, isobutyl alcohol was an unwanted by-product of the propylene Oxo reaction. Indeed, isobutyraldehyde the precursor of isobutyl alcohol was occasionally burned for fuel. However, more recentiy isobutyl alcohol has replaced -butyl alcohol in some appHcations where the branched alcohol appears to have preferred properties and stmcture. However, suppHes of isobutyl alcohol have declined relative to overall C-4 alcohols, especially in Europe, with the conversion of many Oxo plants to rhodium based processes which give higher normal to isobutyraldehyde isomer ratios. Further the supply of isobutyl alcohol at any given time can fluctuate greatly, since it is the lowest valued derivative of isobutyraldehyde, after neopentyl glycol, methyl isoamyl ketone and certain condensation products (10). 

The two isomeric butanals, n- and isobutyraldehyde, C HgO, are produced commercially abnost exclusively by the Oxo Reaction of propylene. They also occur naturally ia trace amounts ia tea leaves, certain oils, coffee aroma, and tobacco smoke. 

The earhest commercial route to -butyraldehyde was a multistep process starting with ethanol, which was consecutively dehydrogenated to acetaldehyde, condensed to crotonaldehyde, and reduced to butyraldehyde. In the late 1960s, production of -butyraldehyde (and isobutyraldehyde) in Europe and the United States switched over largely to the Oxo reaction of propylene. 

Branched-Chain Carboxylic Acids. Branched-chain acids such as 2-methylbutyric, 3-methylbutyric, isooctanoic, and isononanoic acids are produced by the oxo reaction, giving first the corresponding aldehyde, which is then oxidized to the acid. 2-EthyIhexanoic acid is produced by the aldol route from butyaldehyde in three steps aldol condensation hydrogenation of the carbon—carbon double bond and oxidation of the branched-chain saturated aldehyde to 2-ethyIhexanoic acid (see Carboxylic Acids, branched-chain acids). 

C-19 dicarboxyhc acid can be made from oleic acid or derivatives and carbon monoxide by hydroformylation, hydrocarboxylation, or carbonylation. In hydroformylation, ie, the Oxo reaction or Roelen reaction, the catalyst is usually cobalt carbonyl or a rhodium complex (see Oxo process). When using a cobalt catalyst a mixture of isomeric C-19 compounds results due to isomerization of the double bond prior to carbon monoxide addition (80). 

Thiophene, tetrahydro-2-methyl-synthesis, 4, 901 Thiophene, tetrahydro-2-oxo-reactions, 4, 857 Thiophene, tetrahydro-3-oxo-reactions, 4, 857 synthesis, 4, 876-877 Thiophene, tetrahydro-2-phenyl-synthesis, 4, 865 Thiophene, tetraiodo-synthesis, 4, 934... 

Examples are given of common operations such as absorption of ammonia to make fertihzers and of carbon dioxide to make soda ash. Also of recoveiy of phosphine from offgases of phosphorous plants recoveiy of HE oxidation, halogenation, and hydrogenation of various organics hydration of olefins to alcohols oxo reaction for higher aldehydes and alcohols ozonolysis of oleic acid absorption of carbon monoxide to make sodium formate alkylation of acetic acid with isobutylene to make teti-h ty acetate, absorption of olefins to make various products HCl and HBr plus higher alcohols to make alkyl hahdes and so on. 

Synthesis gas is also an important building block for aldehydes from olefins. The catalytic hydroformylation reaction (Oxo reaction) is used with many olefins to produce aldehydes and alcohols of commercial importance. 

Linear alcohols used for the production of ethoxylates are produced by the oligomerization of ethylene using Ziegler catalysts or by the Oxo reaction using alpha olefins. 

Linear alcohols (C12-C26) are important chemicals for producing various compounds such as plasticizers, detergents, and solvents. The production of linear alcohols by the hydroformylation (Oxo reaction) of alpha olefins followed by hydrogenation is discussed in Chapter 5. They are also produced by the oligomerization of ethylene using aluminum alkyls (Ziegler catalysts). 

The mechanism for hydrosilylation in Figs. 6 and 7 clearly has much in common with suggestions regarding homogeneous transition metal catalysis for other processes involving olefins, such as hydrogenation, isomerization, the oxo reaction, and oligo- and polymerization. 

The strategy of using two phases, one of which is an aqueous phase, has now been extended to fluorous . systems where perfluorinated solvents are used which are immiscible with many organic reactants nonaqueous ionic liquids have also been considered. Thus, toluene and fluorosolvents form two phases at room temperature but are soluble at 64 °C, and therefore,. solvent separation becomes easy (Klement et ai, 1997). For hydrogenation and oxo reactions, however, these systems are unlikely to compete with two-phase systems involving an aqueous pha.se. Recent work of Richier et al. (2000) refers to high rates of hydrogenation of alkenes with fluoro versions of Wilkinson s catalyst. De Wolf et al. (1999) have discussed the application and potential of fluorous phase separation techniques for soluble catalysts. 

It is possible to synthesize cobalt complexes which are soluble in polyethylene glycols and not in. solvents like hexane, hexene, heptenal etc. Ritter et al. (1996) have reported the oxo reaction of 1-hexene in such a system. 

Buhling et al. (1995) have used amphiphilic ligands in oxo-reactions, where with a pH swing the catalyst is made organic or water soluble (ligand Ph2Ar(P) with Ar = 3-hydroxy phenyl or 4- caroxy phenyl). 

Monflier et al. (1995) have intensified the rate of the oxo reaction of sparingly soluble olefins like 1-decene using dimethyl p-cyclodextrine, which seems to form inclusion complexes with the olefin and deliver it in the aqueous phase. 

The first stage of the process is a hydroformylation (oxo) reaction from which the main product is n-butyraldehyde. The feeds to this reactor are synthesis gas (CO/H2 mixture) and propylene in the molar ratio 2 1, and the recycled products of isobutyraldehyde cracking. The reactor operates at 130°C and 350 bar, using cobalt carbonyl as catalyst in solution. The main reaction products are n- and isobutyraldehyde in the ratio of 4 1, the former being the required product for subsequent conversion to 2-ethylhexanol. In addition, 3 per cent of the propylene feed is converted to propane whilst some does not react. 

Biphasic techniques for recovery and recycle are among the recent improvements of homogeneous catalysis - and they are the only developments which have been recently and successfully applied in the chemical industry. They are specially introduced into the hydroformylation (or "oxo") reaction, where they form a fourth generation of oxo processes (Figure 5.1 [1]). They are established as the "Ruhrchemie/Rhone-Poulenc process" (RCH/RP) [2] cf. also Section 5.2.4.1), with annual production rates of approximately 800,000 tonnes y"1 (tpy). 

Whereas this important quotient is calculated solely from the product spectrum, process simplifications are a consequence of combining the rhodium catalyst with the special two-phase process. Compared with the conventional oxo process and with other variants (which, for example, include disadvantegeously thermal separation of the oxo reaction products from the catalyst) the procedure is considerably simplified (as shown in several papers, e.g., [2,12]). 

The hydroformylation reaction was discovered by Otto Roelen in 1938 (2,3) while investigating the influence of olefins on the Fischer-Tropsch reaction (/). Particularly in commercial publications, it has been termed the oxo reaction the more proper term, hydroformylation, was proposed by Adkins (4). 

Oxo processes, 13 768 17 725 for amyl alcohols, 2 770-771 described, 2 36-41 major producers using, 2 29-3 It for producing odd-numbered higher alcohols, 2 1, 10 5 215-217 Oxo reaction, in higher olefins, 17 712 Oxosuccinic acid, 23 419 Oxprenolol, molecular formula and structure, 5 156t Ox-Tran instruments, 3 402 Oxyacanthine, 2 88 Oxyacetylene flame, 1 221 Oxy acids... 

Non-corrin cobalt has a number of interesting applications in the chemical industry, for example in the hydroformylation (OXO) reaction between CO, H2 and olefins. A number of non-corrin Co-containing enzymes have been described, including methionine aminopep-tidase, prolidase, nitrile hydratase and glucose isomerase. We describe the best characterized of these, namely the E. coli methionine aminopeptidase, a ubiquitous enzyme, which cleaves N-terminal methionine from newly translated polypeptide chains. The active site of the enzyme (Figure 15.13) contains two Co(II) ions that are coordinated by the side-chain atoms of five amino acid residues. The distance between the two Co2+ is similar to that between the two Zn2+ atoms in leucine aminopeptidase, and indeed the catalytic mechanism of methionine aminopeptidase shares many features with other metalloproteases, in particular leucine aminopeptidases. 

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