Pyrolysis cation effects

Cationic Effects During Lignite Pyrolysis and Combustion... 

The requirement for AlCh adds some obvious limitations, but a modest number of substituted arenes have been successfully coordinated to the [FeCp]+ unit. Photoinduced arene exchange has been described43 and is particularly effective with the -r -chlorobenzene-r -cyclopentadienyliron cation without the need for Lewis acids.42 More basic (electron rich) arenes readily replace chlorobenzene, leading to FeCp cation complexes of O-phenylethyl-p-toluenesulfonate and variously substituted thiophenes.42 The charged complexes are not purified by conventional organic techniques, such as chromatography, but re-crystallization is possible. The complexes are very air and heat stable again, methods of removal of the arene from the Fe are few. The simplest is pyrolysis at >200 C.46... 

The formation of levoglucosan and levoglucosenone is found to be strongly dependent on the presence of catalytic amounts of various cations during pyrolysis. However, the literature is inconsistent regarding the effect of these cations. By varying the amount of acid catalyst used, Faix et al. were able to control the relative amount of the two products.441,442... 

Although previous researchers have studied the effects of cations on the pyrolysis of carboxyl groups, most of the work has been concerned with weight loss as a function of temperature and/or the evolution of carbon oxides. Little work has been concerned with direct determination of the kinetics of decarboxylation. Table VIII... 

Removal of one electron should make no difference to the relative stabilities of polyene molecule ions or even electron polyene fragments as compared to their neutral counterparts, e.g. butadiene and the allyl radical should have the same relative stabihties as the butadiene molecule ion, and the allyl cation. Removal of one electron will, however, alter the stabihties, and thus the reactivities of cychc polyenes. The molecule ions of aromatic hydrocarbons will be substantially less aromatic then their neutral counterparts. Correspondingly the molecule ions of antiaromatic hydrocarbons will not be as antiaromatic as their neutral analogs, e.g. cyclobutadiene + should be relatively more stable than cyclobutadiene. The largest charge effects in hydrocarbons will be observed in nonaltemant ) monocychc hydrocarbons. The cyclopropenium ion 7 and the tropillium ion 2 are both strongly aromatic as compared to their neutral analogs. Consequently CsHs is a very common ion in the mass spectra of hydrocarbons while cyclopropene is not a common product of hydrocarbon pyrolysis or photo-... 

Many rDA reactions are carried out at temperatures of 150 C or more in solution phase and often at temperatures of 400-600 C using the flash vapor pyrolysis (FVP) method individual conditions are referenced throughout the text. However, an accelerating effect by anionic, cationic and radical substimtion on either the dienophile or at the termini of the diene fragments has been predicted by Carpenter.Experimentally, this prediction has been substantiated only for anionic substitution. In 1967, Hart reported what is likely the first example of an oxyanion-accelerated rDA reaction. Both oxyanionic " and car-banionic substituents accelerate the cycloreversion reaction such that they proceed rapidly at room temperature (for example, equation 3). In addition, acid-catalyzed rDA reactions have been reported in which protonation effectively makes the dienophile fragment of the adduct more electron deficient. Grieco has utilized a room temperature retro aza DA reactitm useful for the N-methylation of dipeptides and amino acid derivatives (equatitm 4). ... 

The first effective synthesis of CgFgAsFfi employed 02AsF as the oxidizer of C F dissolved in liquid WPg. This solvent not only provided the desirable diluent effect for this hot reaction but its relatively high heat capacity also aided in preservation of a lower temperature. These are essential requirements for high-yield syntheses of C5F(AsF and its monocyclic relatives, since all are thermally unstable at ordinary temperatures. In more recent work sulfuryl chloride fluoride has been used as the diluent and moderator and the low working temperatures have resulted in greatly improved yields. Nevertheless, even with SO2CIF, pyrolysis products from the salts are always observed and a quantitative yield has never been obtained for any of the monocyclic cation salts. For these and other reasons the salt composition in each Case has been determined from the stoichiometry of the salt pyrolysis products and other reaction stoichiometries. 

Pyrolysis of dihalocyclopropanes was studied along with the effects of electrophilic reagents, and confirms the foregoing results (33-37). In many cases, those authors observed that polymeric residues, in addition to ally lie and diene-type products, were present at the end of pyrolysis. The formation of these polymers confirms the hypothesis that the dihalocyclopropanes are monomers that can be polymerized either by cationic processes or by the action of transition-metal complex catalysts. 

Restovic A, Rios E, Barbato S, Ortiz J, Gautier JL (2002) Oxygen reduction in alkaline medium at thin MnxCo3 x04 (0 < x < 1) spinel films prepared by spray pyrolysis. Effect of oxide cation composition on the reaction kinetics. J Electroanal Chem 522(2) 141-151... 

Veses, A., et al., 2015. Catal3dic upgrading of biomass derived pyrolysis vapors over metal-loaded ZSM-5 zeolites effect of different metal cations on the bio-oH final properties. Microporous and Mesoporous Materials 209 (0), 189—196. 

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