Kinetics of olefin oxidations

Smidt, J. and Sieber, R. (1959) Reactions of palladium dichloride with olefinic double bonds. Angew. Chem., 71, 626. Moiseev, I.I., Levanda, O.G. and Vargaftik, M.N. (1974) Kinetics of olefin oxidation by tetrachloropalladate in aqueous solution. /. Am. Chem. Soc., 96, 1003. 

UV-Vis spectrophotometry has also been helpful to study the kinetics of olefin oxidation with hydrogenperoxide using methyltrioxorhenium (MTO) in the ionic liquids [C2mim][BF4], [C4mim][BF4], [C4mim][N03] and [C4py][BF4] [23],... 

Kinetics of olefin oxidation over copper catalysts that are first order in oxygen and zero order in olefin have suggested reaction of strongly... 

Bolland JL. Kinetic of olefin oxidation. Quart Rev Chem Soc 1949 3 1-21. 

A similar mechanism of chain oxidation of olefinic hydrocarbons was observed experimentally by Bolland and Gee [53] in 1946 after a detailed study of the kinetics of the oxidation of nonsaturated compounds. Miller and Mayo [54] studied the oxidation of styrene and found that this reaction is in essence the chain copolymerization of styrene and dioxygen with production of polymeric peroxide. Rust [55] observed dihydroperoxide formation in his study of the oxidation of branched aliphatic hydrocarbons and treated this fact as the result of intramolecular isomerization of peroxyl radicals. 

This mechanism is consistent with a number of observations. Kinetic studies on prolyl 4-hydroxylase [223] and thymine hydroxylase (EC 1.14.11.6) [224] suggest that cofactor binds first, followed by 02. The bound 02 appears to have superoxide character, as superoxide scavengers are competitive inhibitors of 02 consumption [225,226], It is also clear that the oxidative decarboxylation of the keto acid is a distinct phase of the mechanism from the alkane functionalization step, as these two phases can be uncoupled, particularly when poor substrate analogs are employed [227-229], Evidence for an Fe(IV) = 0 intermediate derives from studies with substrate analogs. Besides the hydroxylation of the 5-methyl group of thymine, thymine hydroxylase can also catalyze ally lie hydrox-ylations, epoxidation of olefins, oxidation of sulfides to sulfoxides, and N-de-... 

Kinetic experiments on the MTO/H2O2 system have indicated that both the mono- and bis(peroxo) species are active species in the olefin oxidation reaction. The rate constants of olefin oxidation by the mono- and bis(peroxo) species were found to be in the same order of magnitude, indicating that both complexes can be the predominant active species, depending on both the rate of formation of these species and the H2O2 concentration [20, 22]. 

Oxidative addition reactions of dihydrogen , iodine ", alkyl halides and Hg(CN)2 to carbonyl, olefin or phosphine substituted derivatives of rhodium(I) and iridium(I) have been described. In order to determine the effect on the rate of the reaction, the kinetics of the oxidative addition of Hg(CN)2 to Rh(dik)(P(OPh)3)2 has been studied . A second-order rate law coupled to large negative values of the activation entropy suggest an associative mechanism which probably proceeds via a cyclic three-centred transition state (equation 58). Analogous results were obtained with Ir(dik)(cod) . ... 

Because of the ability of PdCl2 in aqueous systems to catalyze the oxidation of simple olefins to the corresponding aldehyde or ketone (268), considerable attention has been devoted to the study of the nature of the complex in solution and of the kinetics of the oxidation reaction. This subject has been thoroughly reviewed (4, 556). Moiseev and coworkers 414, 467, 468) have established that the complex equilibria in solution are as represented by Eqs. (6) and (7)... 

There has been several kinetic studies of olefin oxidation in acetic acid (189, 196, 207, 274). However, all these studies were undertaken before a knowledge of the equilibria involving the Pd(II) species was... 

Okada, H., Noma, T., Katsuyama, Y., Hashimoto, H. Reactions of transition-metal-olefin complexes. III. Kinetics of the oxidation of substituted styrenes catalyzed by palladium salts in aqueous tetrahydrofuran. Bull. Chem. Soc. Jpn. 1968,41, 1395-1400. 

Zaw, K., Henry, P. M. Oxidation of olefins by palladium(ll). 12. Product distributions and kinetics of the oxidation of 3-buten-2-ol and 2-buten-1-ol by tetrachloropalladate (PdCU-) in aqueous solution. J. Org. Chem. 1990, 55,1842-1847. 

On platinum catalysts, the kinetics of HC oxidation, NO reduction and NO oxidation are strongly dependant on the hydrocarbon nature. Those mechanisms occur at lower temperature with long chain alkanes than with olefins and these alkanes lead to a higher N2O selectivity than unsaturated molecules. 

In summary, although much is known about the mechanism of olefin oxidation over cuprous oxide, the picture is far from complete. Electronic factors governing the rates of reaction at the surface are unquestionably important. Kinetics have not yet clearly defined the rate-limiting step. Initial attack on an olefin of appropriate structure occurs by abstraction of an allylic hydrogen, and is followed by further reaction at either end of an adsorbed allylic intermediate. Inclusion of a hetero atom (0, N) occurs after the second abstraction. 

Bolland, J., G. Gee, Kinetic studies in the chemistry of rubber and related materials III. Thermo chemistry and mechanisms of olefin oxidation, Trans. Faraday Soc., 42, p. 244, 1946. 

T[[dotb]he nature of the initial attack by the water (eq. 10) is a matter of some controversy (205,206). Stereochemical and kinetic studies of model systems have been reported that support trans addition of external water (207,208) or internal addition of cis-coordinated water (209), depending on the particular model system under study. Other paHadium-cataly2ed oxidations of olefins ia various oxygen donor solvents produce a variety of products including aldehydes (qv), ketones (qv), vinyl acetate, acetals, and vinyl ethers (204). However the product mixtures are complex and very sensitive to conditions. 

The kinetics of formation and hydrolysis of /-C H OCl have been investigated (262). The chemistry of alkyl hypochlorites, /-C H OCl in particular, has been extensively explored (247). /-Butyl hypochlorite reacts with a variety of olefins via a photoinduced radical chain process to give good yields of aUyflc chlorides (263). Steroid alcohols can be oxidized and chlorinated with /-C H OCl to give good yields of ketosteroids and chlorosteroids (264) (see Steroids). /-Butyl hypochlorite is a more satisfactory reagent than HOCl for /V-chlorination of amines (265). Sulfides are oxidized in excellent yields to sulfoxides without concomitant formation of sulfones (266). 2-Amino-1, 4-quinones are rapidly chlorinated at room temperature chlorination occurs specifically at the position adjacent to the amino group (267). Anhydropenicillin is converted almost quantitatively to its 6-methoxy derivative by /-C H OCl in methanol (268). Reaction of unsaturated hydroperoxides with /-C H OCl provides monocyclic and bicycHc chloroalkyl 1,2-dioxolanes. 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

These ions, with the exception of Pb(IV), form complexes with olefins and this process is a preliminary to oxidation when this occurs. A recent review of the action of Pd(II) covers aspects of structure and bonding as well as kinetics, and a similar but older, review exists for Hg(II) . The oxidation of olefins by thallic... 

These are oxidised by both Fe(III) and Cu(II) octanoates (denoted Oct) in nonpolar solvents at moderate temperatures . 80-90 % yields of the corresponding disulphide are obtained with Fe(III) and this oxidant was selected for kinetic study, the pattern of products with Cu(II) being more complex. The radical nature of the reaction was confirmed by trapping of the thiyi radicals with added olefins. Simple second-order kinetics were observed, for example, with l-dodecane thiol oxidation by Fe(Oct)3 in xylene at 55 °C (fcj = 0.24 l.mole . sec ). Reaction proceeds much more rapidly in more polar solvents such as dimethylformamide. The course of the oxidation is almost certainly... 

The present economic and environmental incentives for the development of a viable one-step process for MIBK production provide an excellent opportunity for the application of catalytic distillation (CD) technology. Here, the use of CD technology for the synthesis of MIBK from acetone is described and recent progress on this process development is reported. Specifically, the results of a study on the liquid phase kinetics of the liquid phase hydrogenation of mesityl oxide (MO) in acetone are presented. Our preliminary spectroscopic results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups coordinated to the catalyst. An empirical kinetic model was developed which will be incorporated into our three-phase non-equilibrium rate-based model for the simulation of yield and selectivity for the one step synthesis of MIBK via CD. 

A detailed study of the mechanism of the insertion reaction of monomer between the metal-carbon bond requires quantitative information on the kinetics of the process. For this information to be meaningful, studies should be carried out on a homogeneous system. Whereas olefins and compounds such as Zr(benzyl)4 and Cr(2-Me-allyl)3, etc. are very soluble in hydrocarbon solvents, the polymers formed are crystalline and therefore insoluble below the melting temperature of the polyolefine formed. It is therefore not possible to use olefins for kinetic studies. Two completely homogeneous systems have been identified that can be used to study the polymerization quantitatively. These are the polymerization of styrene by Zr(benzyl)4 in toluene (16, 25) and the polymerization of methyl methacrylate by Cr(allyl)3 and Cr(2-Me-allyl)3 (12)- The latter system is unusual since esters normally react with transition metal allyl compounds (10) but a-methyl esters such as methyl methacrylate do not (p. 270) and the only product of reaction is polymethylmethacrylate. Also it has been shown with both systems that polymerization occurs without a change in the oxidation state of the metal. 

Both these reactions occur rapidly. The kinetics and the products of co-oxidation of aldehydes and olefins were studied by Emanuel and coworkers [47-49], The values of the rate constants of the addition of acylperoxyl radical to olefins are presented in Table 8.8. The experimental data on aldehyde co-oxidation are discussed in monographs [4-6]. 

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