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Kinetics of carbonylation

Figure 4. Kinetics of carbonyl group formation at 1714 cm- in polypropylene samples (0) and ( ) ozone and UV light (L2) (4) and (A) ozone only (0) and ( ) ATR spectra (A) and (A) transmission spectra. Figure 4. Kinetics of carbonyl group formation at 1714 cm- in polypropylene samples (0) and ( ) ozone and UV light (L2) (4) and (A) ozone only (0) and ( ) ATR spectra (A) and (A) transmission spectra.
There have been three primary motives behind the study of metal carbonyl photochemistry in the gas phase first, to discover the shapes of metal carbonyl fragments in the absence of perturbing solvents or matrices second, to probe the effect of uv photolysis wavelength on product distribution and third, to measure the reaction kinetics of carbonyl fragments. All three areas have already proved fruitful. The photochemistry of two molecules, Fe(CO)5 and Cr(CO)6, has been studied in detail. [Pg.300]

Figure 2.26. Kinetic of carbonyl groups change in CA-film containing 2% BA and PAC in the process of irradiation by mercury-quartz lamp 1 - CA without additive, 2 - CA+BA, 3 - CA+XXXIV, 4 -CA+XXXV, 5 - CA+XXXVL 6 - CA+XXXVll. Figure 2.26. Kinetic of carbonyl groups change in CA-film containing 2% BA and PAC in the process of irradiation by mercury-quartz lamp 1 - CA without additive, 2 - CA+BA, 3 - CA+XXXIV, 4 -CA+XXXV, 5 - CA+XXXVL 6 - CA+XXXVll.
A number of studies of the important (non-phosgene) route to aryl isocyanates via carbonylation of nitro compounds have appeared. In a comparative study of Rh(I), Ir(I), Pd(I) and Pd(II) catalysts, Bu,N+[RhX2(CO)2] (X Cl, Br, I) was most effective giving 83-89% PhNCO with 100% PhN02 conversion at 125 C under 80 atm CO pressure . The kinetics of carbonylation by [PdCl2py2l at 170-230 C and 23-94 atm CO pressure are first order in p[CO] and catalyst and zero order in PhNOj . The reductive N-carbonylation of nitroarenes to the carbamates is catalysed by tPtCl2 (PPh3 >2] in ethanol, promoted by Lewis acids (SnCli,... [Pg.387]

In order to understand why the notoriously water-sensitive metal-mediated reactions can proceed in water at all, it is necessary to look at three basic aspects (1) the fundamental bonding in organometallic compounds, (2) the kinetics of the hydrolysis of C—M bonds, and (3) the kinetics of carbonyl addition (and other nucleophilic reactions) by C—M bonds. [Pg.93]

Fig. 3.62. Kinetics of carbonyl groups (CO) formation in poly(styrene-co-butadiene) during UV irradiation. (Reprinted with permission from [293], Pergamon Press Ltd, Oxford, England.)... Fig. 3.62. Kinetics of carbonyl groups (CO) formation in poly(styrene-co-butadiene) during UV irradiation. (Reprinted with permission from [293], Pergamon Press Ltd, Oxford, England.)...
The kinetics of carbonylation of trans- [Pd(PR3)2(R )X], [Pd(dmpe)(R)X], and [Pd(dppe)(R)X] have been investigated relative to the solvento cations derived fitom them by use of silvo tetrafluoro-borate. The rate of migratory insertion is 10 faster for die cationic species in the chelated ligand complexes where the vacant site is cu to the alkyl group there is a rate enhanc ent of 3-4 times compared to the trans complexes. The insertion of benzylisonitrile was also studied. ... [Pg.311]

Figure 3.7 Experimental kinetics of carbonyl build-up during thermal oxidation at 80°C for pure HDPE ( ) and HDPE + 0.016% Vitamin E ( ) and simulations by the model with kjj values given above. Figure 3.7 Experimental kinetics of carbonyl build-up during thermal oxidation at 80°C for pure HDPE ( ) and HDPE + 0.016% Vitamin E ( ) and simulations by the model with kjj values given above.
The composition of the products of reactions involving intermediates formed by metaHation depends on whether the measured composition results from kinetic control or from thermodynamic control. Thus the addition of diborane to 2-butene initially yields tri-j iAbutylboraneTri-j -butylborane. If heated and allowed to react further, this product isomerizes about 93% to the tributylborane, the product initially obtained from 1-butene (15). Similar effects are observed during hydroformylation reactions however, interpretation is more compHcated because the relative rates of isomerization and of carbonylation of the reaction intermediate depend on temperature and on hydrogen and carbon monoxide pressures (16). [Pg.364]

Chapters 1 and 2. Most C—H bonds are very weakly acidic and have no tendency to ionize spontaneously to form carbanions. Reactions that involve carbanion intermediates are therefore usually carried out in the presence of a base which can generate the reactive carbanion intermediate. Base-catalyzed condensation reactions of carbonyl compounds provide many examples of this type of reaction. The reaction between acetophenone and benzaldehyde, which was considered in Section 4.2, for example, requires a basic catalyst to proceed, and the kinetics of the reaction show that the rate is proportional to the catalyst concentration. This is because the neutral acetophenone molecule is not nucleophihc and does not react with benzaldehyde. The much more nucleophilic enolate (carbanion) formed by deprotonation is the reactive nucleophile. [Pg.229]

There have been numerous studies of the rates of deprotonation of carbonyl compounds. These data are of interest not only because they define the relationship between thermodynamic and kinetic acidity for these compounds, but also because they are necessary for understanding mechanisms of reactions in which enolates are involved as intermediates. Rates of enolate formation can be measured conveniently by following isotopic exchange using either deuterium or tritium ... [Pg.419]

Kinetic studies on substitution reactions of carbonyl metal complexes. H. Werner, Angew. Chem., Int. Ed. Engl., 1968, 7,930-941 (106). [Pg.55]

The equilibrium constant K is the same for R =t-C4HJ and t-CsHi. As also the rate constants of carbonylation and decarbonylation are about equal for these two ions, it is concluded that both the thermodynamics and the kinetics of the carbonylation reaction are independent of the structure of R+, if R+ is an acyclic tertiary alkyl cation. This agrees with former findings (Brouwer, 1968) on the relative stabilities of such ions. [Pg.33]

This section deals with the kinetics of the carbonylation of some stabilized cations (cyclopropylcarbonium ions, allylic and homoaUylic... [Pg.46]

For the determination of stabilizations of carbonium ions the equilibrium constants of carbonylation-decarbonylation have been used in previous Sections. For the ions discussed in this Seetion, however, the rate constants of decarbonylation are not known and, therefore, the rate constants of carbonylation will be used as a criterion for such stabilizations. This kinetic criterion is a useful indicator if there are no significant steric factors in the carbonylation step and if this step is indeed rate-determining in the overall process (Hogeveen and Gaasbeek, 1970). The following rate constants in Table 2 are of particular importance. [Pg.47]

Secondly, the stabilization of alkylcarbonium ions can be conveniently determined by measuring the equilibrium constants of the carbonylation-decarbonylation reactions. For some cases the rates of carbonylation are used as a kinetic criterion for stabilization. [Pg.51]

B. l,3>2>Dioxaphospholens.—The kinetics of the addition of trialkyl phosphites to benzil have been investigated spectrophotometrically. The second-order reaction of trimethyl phosphite in dioxan has activation parameters of A// = 8.4 kcal mol and AS = — 47.5 e.u. In benzene the rate constant increases linearly with low concentrations of added organic acid and decreases linearly with low concentrations of added base. The Diels-Alder mechanism is considered unlikely on the basis of these data, and the slow step is considered to be nucleophilic addition of the phosphite to the carbon of the carbonyl group (see Scheme). [Pg.34]

ATR spectra show that oxygen groups are located at the surface to the depth of 0.6 /l m. Kinetic curves of carbonyl groups formation in different experimental conditions are shown in Fig.4. [Pg.190]

ESCA spectra, 190,192/ kinetic curves of carbonyl formation, 190,191/ wettability, 193/... [Pg.481]

The UV-spectra of azolides have already been discussed in the context of hydrolysis kinetics in Chapter 1. Specific infrared absorptions of azolides were mentioned there as well increased reactivity of azolides in nucleophilic reactions involving the carbonyl group is paralleled by a marked shift in the infrared absorption of the corresponding carbonyl bond toward shorter wavelength. For example, for the highly reactive N-acetyl-tetrazole this absorption is found in a frequency range (1780 cm-1) that is very unusual for amides obviously the effect is due to electron attraction by the heterocyclic sys-tem.[40] As mentioned previously in the context of hydrolysis kinetics of both imidazo-... [Pg.35]

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. [Pg.261]

There are also voices critical of the rTCA cycle Davis S. Ross has studied kinetic and thermodynamic data and concludes that the reductive, enzyme-free Krebs cycle (in this case the sequence acetate-pyruvate-oxalacetate-malate) was not suitable as an important, basic reaction in the life evolution process. Data on the Pt-catalysed reduction of carbonyl groups by phosphinate show that the rate of the reaction from pyruvate to malate is much too low to be of importance for the rTCA cycle. In addition, the energy barrier for the formation of pyruvate from acetate is much too high (Ross, 2007). [Pg.198]

Despite the considerable amount of information that has been garnered from more traditional methods of study it is clearly desirable to be able to generate, spectroscopically characterize and follow the reaction kinetics of coordinatively unsaturated species in real time. Since desired timescales for reaction will typically be in the microsecond to sub-microsecond range, a system with a rapid time response will be required. Transient absorption systems employing a visible or UV probe which meet this criterion have been developed and have provided valuable information for metal carbonyl systems [14,15,27]. However, since metal carbonyls are extremely photolabile and their UV-visible absorption spectra are not very structure sensitive, the preferred choice for a spectroscopic probe is time resolved infrared spectroscopy. Unfortunately, infrared detectors are enormously less sensitive and significantly slower... [Pg.86]

These problems can be somewhat overcome by a study of reactions in solution where much greater densities are possible than in the gas phase and fast bimolecular reaction are diffusion limited [1,28,29]. However, since coordinatively unsaturated metal carbonyls have shown a great affinity for coordinating solvent we felt that the appropriate place to begin a study of the spectroscopy and kinetics of these species would be in a phase where there is no solvent the gas phase. In the gas phase, the observed spectrum is expected to be that of the "naked" coordinatively unsaturated species and reactions of these species with added ligands are addition reactions rather than displacement reactions. However, since many of the saturated metal carbonyls have limited vapor pressures, the gas phase places additional constraints on the sensitivity of the transient spectroscopy apparatus. [Pg.87]


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