Aldehydes linear /branched

Entry Catalyst Init TOF (min ) Aldehyde linear branch % isomerization... 

Selectivity refers to the fraction of raw material alkene that is converted to product aldehyde, but since hydroformylation typically gives both a linear and branched isomer, selectivity also refers to the relative amounts of each. The linear branched (l b) ratio is highly catalyst dependant. One must simultaneously consider whether the proposed catalyst will give the desired l b selectivity and also whether the proposed catalyst is feasible for use with the catalyst/product separation technologies. For example, water extraction of a polar product, such as in the hydroformylation of allyl alcohol to give 4-hydroxybutanal, would not work well with a sodium salt of a sulfonated phosphine since both are water soluble. 

A straightforward method for aldolizing unsymmetrical ketones on the more hindered side involves the use of catalytic titanium(lV) chloride in toluene at room temperature. For examples using acyclic and cyclic ketones, and linear, branched, and aromatic aldehydes, the regioselectivity varied from 7 1 to >99 1, while the symanti ratios were moderate to good, and yields were in the range 62-91%. In contrast to other methods, base is not required, and the ketone can be used as is (i.e. the silyl enol ether is not required). 

Other commonly occurring chemical groups in essential oils include aromatics such as /3-phenethyl alcohol, eugenol, vanillin, benzaldehyde, cinnamaldehyde, etc heterocyclics such as indole, pyrazines, t hi azoles, etc hydrocarbons (linear, branched, saturated, or unsaturated) oxygenated compounds such as alcohols, acids, aldehydes, ketones, ethers and macrocyclic compounds such as the macrocyclic musks, which can be both saturated and unsaturated,... 

Increasing the CO partial pressure decreases the hydro-formylation reaction rate and the amount of alkene isomerization side reactions (see Hydrogenation Isomerization ofAlkenes), while increasing the aldehyde linear to branched product ratio. Pino proposed that the apparent marked difference between HCo(CO)4-catalyzed hydroformylation at low and high CO partial pressures was due to the existence of two active catalyst species, HCo(CO)4 and HCo(CO)3, formed from the CO association/dissociation equilibrium shown in... 

The utility of a biphasic fluorous system with Rh(acac)(CO)2/P(C6H4-4-OCH2C7Pi5)3 as the catalyst precursor in the hydroformylation of 1-octene has been reported by Bulto and coworkers. In this system, selectivities of 99% and regioselectivities for the linear aldehyde up to linear/branched = 2.8 were achieved with TOP values of 3 80 h. Although loss of rhodium was observed after the first run, the system could be recycled twice without diminishing activity or selectivity. 

Supported aqueous-phase catalysts can also be used to advantage. These supported catalysts have a thin aqueous film adhering to silica gel that contains the water-soluble complex (131). These catalysts are particularly useful for the hydroformylation of substrates such as oleyl alcohol (132). Since these catalytic reactions occur at the phase boundary, characteristics such as the water content can cause changes both in the reactivity and in the linear branched chain ratio of the product aldehyde. 

Alkane oxidation to alcohols, aldehydes and ketones has been extensively studied and it was found that the smaller linear alkanes show higher turnovers than the longer linear, branched and cyclic alkanes [81]. Although the turnover numbers are found to increase with the addition of methanol as a co-solvent, the general role of the co-solvent in selectivity is still not clear. Catalytic epoxidations of relatively inert alkenes such as propylene and allyl chloride were found to be facile under mild... 

Since its discovery by Roelen in 1938 [l],the hydroformylation process was exclusively based on cobalt as catalyst metal, until the development of rhodium-phosphine complexes in the late 1960s [2]. Industrial efforts have been focused on the preparation of norraaZ-aldehydes (linear aldehydes) from 1-alkenes. In contrast, asymmetric hydroformylation, which requires iso-aldehydes (branched aldehydes) to be formed from 1 -alkenes, was first examined in the early 1970s by four groups independently, using Rh(I) complexes of chiral phosphines as catalysts [3,4,5,6]. Since then, a number of chiral ligands have been developed for... 

A variety of ligand-modified cobalt catalysts have been investigated and a commercial process known as the Shell Process was developed The Shell Process uses tributylphosphine as the modifier, which generates HCo(CO)3PBu3 as the active catalyst species and is substantially more stable than HCo(CO)4. This process gives a higher linear/branched ratio (7.3/1, i.e., 88% linear and 12% branched for the reaction of 1-propene), but the products are alcohols and not aldehydes, and ca. 15% of 1-propene is hydrogenated to propane. These... 

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