Reaction under atmospheric

Recently, Vigil and Willmore [67] have reported mean field and lattice gas studies of the oscillatory dynamics of a variant of the ZGB model. In this example oscillations are also introduced, allowing the reversible adsorption of inert species. Furthermore, Sander and Ghaisas [69] have very recently reported simulations for the oxidation of CO on Pt in the presence of two forms of oxygen, namely chemisorbed atomic O and oxidized metal surface. These species, which are expected to be present for reaction under atmospheric pressure, are relevant for the onset of oscillatory behavior [69]. 

The different ratios of 52/53 produced by cycloadditions performed at atmospheric and high pressure, and the forma tion of the unusual trans adducts 53, have been explained by the facts that (i) Diels-Alder reactions under atmospheric pressure are thermodynamically controlled, and (ii) the anti-endo adducts 52 are converted into the short-lived syn-endo adducts 54 which tautomerize (via a dienol or its aluminum complexes) to 53. The formation of trans compounds 53 by induced post-cycloaddition isomerization makes the method more flexible and therefore more useful in organic synthesis. 

Adeniji, S.A., Kerr, J.A., Williams, M.R. (1981) Rate constants for ozone-alkene reactions under atmospheric conditions. Int. J. Chem. Kinet. 13, 209-217. 

In equation (C), A() (or A 111 as used earlier) is the low-pressure limiting rate constant and Ay is the high-pressure limiting rate constant. Fc is known as the broadening factor of the falloff curve its actual value depends on the particular reaction and can be calculated theoretically. Troe (1979) suggests that for reactions under atmospheric conditions, the value of Aft will be 0.7-0.9, independent of temperature. However, values as low as 0.4 are often observed. The NASA evaluations of stratospheric reactions (DeMore et al., 1997) take Aft = 0.6 for all reactions. The IUPAC evaluation (Atkinson et al., 1997a,b) does not restrict Fc to 0.6. However, it is important to note that the values of A0 and Ay will depend on the value of Fc used to match the experimental data. For example, for reaction (11)... 

Barnes, I., V. Bastian, and K. H. Becker, FTIR Spectroscopic Studies of the C H, S + N02 Reaction under Atmospheric Conditions, Chem. Phys. Lett., 140, 451-457 (1987). 

At high temperatures, such as 900°C, the effect of entropy increase in reaction (272) resulting from the increase in the number of gas molecules outweighs the effect of enthalpy increase due to the reaction consequently, the reaction can proceed in the forward direction to its end under atmospheric pressure, or even at pressures of some tens of atmospheres. At lower temperatures (e.g., 300°C) the reaction under atmospheric pressure can go completely in the reverse direction. In the intermediate temperature range and at pressures near 1 atm, the substances entering (272) coexist at equilibrium in comparable amounts. 

Direct Kinetic and Mechanistic Study of the OH-Dimethyl Sulfide Reaction Under Atmospheric Conditions... 

Under extremely high pressure, the isonitrile-palladium catalyst promotes intramolecular bis-silylation of bis(silyl)acetylenes 51 to give tetrakis(silyl) alkenes 52, which are otherwise difficult to synthesize the reaction under atmospheric pressure hardly proceeds even at 200°C (Eq. 22) [48,49]. 

On the other hand, for theUS Y-catalyzed alkylation of isobutane with frans-2-butene at high levels of conversion (100%), adding SCCO2 decreased the catalytic longevity and product selectivity. The alkylation of toluene with propylene over siUcon-modifled HZSM-5 zeolite using SCCO2 increased the yield of cymene and reduced the cracking of propylene compared with the reaction under atmospheric pressure (Scheme 41). ... 

Chen et al. have hypothesized that substituted acrylates may provide stereo-and/or stereoelectronic effects that stabilize the oxy anion intermediate, which would shift the equilibrium forward and subsequently accelerate the following aldol reaction. Thus, they screened a range of substituted acrylates and found that an extremely rapid rate can be achieved by using a-naphthyl acrylate as the Michael acceptor for the MBH reaction.The reaction of a-naphthyl acrylate with both aliphatic and aromatic aldehydes in the presence of DABCO provided the desired adducts 13 in reasonable yields within 20 min, which is one of the best rate acceleration systems for a wide range of aldehydes in the MBH reaction under atmospheric pressure (Scheme 2.10). 

The purpose of this research was to obtain kinetic data for the reaction of ozone with cycloalkenes and to determine the formation yields of hydroxyl radicals in these reactions under atmospheric conditions. 

Sealed tube reactions are sometimes used when safer reactions under atmospheric conditions failed, and as you can guess from the name, basically a set of reactants are sealed in a tube and heated to drive the reaction to the desired products. However, any chemical heated in a closed system will build up pressure that can make the tube the source of a possible explosion (see Incident 7.3.7.1). 

The mechanisms of the reactions of HO radical with esters (Me formate, Et formate, Et acetate, and Pr acetate) have been explored through quantum chemical and computational kinetics calculations. These reactions, under atmospheric conditions, occur via a complex mechanism, whereby reversible formation of a reactant complex is followed by irreversible H abstraction from C atoms in the a position to alkoxy oxygen. Activation of this position is a consequence of the donor ability of such oxygen and the formation of hydrogen bonds in the transition stmcture. The order of site reactivities for H abstraction was found to be -OCHj- > -CCHj- > HC(0)0- > -OCH3 > CH3C(0)0-. ... 

Sudo A, Morioka Y, Sanda F, Endo T (2004) JV-Tosyl aziridine, a new substrate fm chemical fixation of carbon dioxide via ring expansimi reaction under atmospheric pressure. Tetrahedron Lett 45 1363—1365... 

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