Gas-phase format

It is highly unlikely that all organic molecules have gas-phase formation routes and many may be formed on the surface of dust grains, probably with ice mantles,... 

Hehre and co-workers (DeFrees et al., 1977, 1979a) have published both experimental and theoretical evidence in support of negative ion (anionic) hyperconjugation. These workers determined the free energies for the gas-phase hydron3 transfer equilibria (31), (32) and (33) by pulsed ion cyclotron resonance spectroscopy (Wolf et al., 1976). These equilibria, which involve the gas-phase formation of a methylamino, a methoxy and a thiomethoxy anion, all lie to the right, i.e. the formation of the isotopically light anion is favoured. These results were rationalized in terms of the MO... 

A review article on the CVD processes used to form SiC and Si3N4 by one of the pioneers in this area, Erich Fitzer [Fitzer, E., and D. Hegen, Chemical vapor deposition of silicon carbide and silicon nitride—Chemistry s contribution to modem silicon ceramics, Angew. Chem. Int. Ed. Engl, 18, 295 (1979)], describes the reaction kinetics of the gas-phase formation of these two technical ceramics in various reactor arrangements (hot wall, cold... 

The gas-phase formation of metalloporphyrin ions (M(P)+) has been known for a long time, since the early mass-spectra studies of metalloporphyrins (97,98). Such gas-phase studies allow determination of the intrinsic properties of the species, unaffected by solvation, ion pairing, and other effects common to solution chemistry. 

In the previous problem we examined temperature profiles and reactant (SiH4) concentration profiles in a channel-flow chemical vapor deposition (CVD) reactor. At sufficiently high temperatures (and pressures) SM4 undergoes unimolecular decomposition into the species SiH2 and H2. This is followed by numerous reactions of the intermediate species [180]. One such intermediate species formed in the gas phase is Si (i.e., a gas-phase silicon atom). In this problem we consider the gas-phase formation and destruction reactions governing the spatial profiles of Si atoms in a rotating-disk CVD reactor. 

Second-order reactions of type II are probably among the most common of all reactions studied. A few typical examples are the gas-phase formation of hydrogen iodide, II2 + I2 2HIthe reactions of free radicals with molecules, for example, H + Br2 HBr + H the famous synthesis of urea from NH4 and CNO ions the hydrolysis of organic esters in non-aqueous media and the reaction of tertiary alkyl amines with alkyl halides to produce quaternary ammonium salts, R3N + R X — R RsN+ +... 

Some examples of fractional-order reactions are the interconversion of ortho- and para-H [where the rate is %-order n = %)] the gas-phase formation of phosgene, " CO + CI2 COCI2 (which has an over-all order of being %-order with respect to CI2 and first-order with respect to CO) and the chlorine-catalyzed decomposition of ozone, 20s 302 (which... 

For the case of high temperatures found in the vicinity of hot stars, or in cloud regions under the influence of a shock wave, or in ionized nebulae, several authors have suggested (c.f. Jura, 1975, Dalgamo and McCray 1973) a gas phase formation scheme which could be a significant source for molecular hydrogen, Hj. The associative detachment reaction... 

In the gas phase formation of ozonide would be unlikely, and the intermediates should live long enough to react with NO2 as in Equations 11 and 12, with CgHe as in 13, 14, 15, and 16, and with O2 as in 17 and 18. However preliminary calculations using Equation 51 indicate that reactions 13, 14, 15, and 16 are too slow to be important in this process. Reactions of intermediates, as in 17 and 18, explain the non-stoichiometric ratio of olefin to O3 in the presence of O2 as observed by Cvetanovic (3) and others. Ozone may also be formed upon reacting with peroxyacyl radicals such as in Equation 31. 

The reaction between nitric radicals and pinonaldehyde (Waengberg et al., 1997) is only one example of the role of organic compounds in the gas phase formation of nitric acid in the atmosphere. 

Extreme °Ne/ Ar and low Ar concentrations in some natural gases are explained by equilibration of an oil phase with the groundwater before gas phase formation. 

The poisoning effects due to the dissociative adsorption of HMDS on catalytic activity of Pt ribbons in methane oxidation depended on the temp, of the interaction At low temp, a multilayer is formed which desorbs at 150 K, with temp, increase several product appears in the gas phase, formation of amorphous carbon and graphitization at above 700 K Three types of behaviour can be distinguished type-A, irreversible adsorption results in poisoning, type-B reversible adsorption results in inhibition, and type-C does not affect the reaction rate... 

The most conventional non-equilibrium plasma-chemical systems that produce diamond films use H2-CH4 mixture as a feed gas. Plasma activation of this mixture leads to the gas-phase formation of hydrogen atoms, methyl radicals (CH3), and acetylene (C2H2), which play a major role in further film growth. Transport of the gas-phase active species to the substrate is mostly provided by diffusion. The substrate is usually made from metal, silicon, or ceramics and is specially treated to create diamond nucleation centers. The temperature of the substrate is sustained at the level of 1000-1300 K to provide effective diamond synthesis. The synthesis of diamond films is provided by numerous elementary surface reactions. Four chemical reactions in particular describe the most general kinetic features of the process. First of all, surface recombination of atomic lydrogen from the gas phase into molecular hydrogen returns back to the gas phase ... 

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