C2H radicals

Having initiated the chemistry within the atmospheric model, the elongation of the carbon-chain polyyne species occurs by successive addition of the C2H radical ... 

We have observed that the radioactive contamination is practically independent of the temperature A9). We believe that this radioactive contamination is due to the presence of traces of radioactive polyethylene resulting from ethylene polymerization. Ethylene can result, in fact, from the disproportionation of C2Hs radicals released by decomposition of ethyl titanium compounds, which derive from the reaction between ethylalu-minum and traces of titanium tetrachloride or other tetravalent titanium compounds that are sometimes present as impurities in the a-titanium trichloride. 

The kinetic studies with ethane have established that reaction of C2H.-> radicals with H2 can occur only to a minor extent the only other possible reactions of C2H5 are with 02 to form either ethylene oxide or acetaldehyde, and these can occur only to a small extent. 

The triple-bonded C2H radical does not seem to react with NO, even when the NO pressure is raised to 30 torr.414 One might have thought that HCN and CO would have been formed. 

Acetylene is the simplest unsaturated hydrocarbons and as such an understanding of its photochemistry is important. The reactions of ethynyl radicals (C H) are important in combustion as well as in the photochemistry of Jupiter and Titan atmospheres, although, unfortunately, C2H radical has apparently only very weak and complex absorption spectra in the visible and ultraviolet region and no LIF has been found. 

The production of acetylene as the major gaseous product in the reaction of butadiyne (equation 9) occurs in part via C2H radicals when short wavelength radiation is used , but with 254 nm radiation it is suggested that a molecular process occurs in a non-linear excited state. The evidence for this additional process is that no C2HD is formed when perdeuteriopropyne is present as a source of deuterium to trap the radicals. 

However, the C2HS radicals are neither purely P or radicals they are somewhere in between because the propagation step in which they take part, viz. 

This mechanism involves the formation of ring-ring aromatics, interconnected by aliphatic chains, which after successive dehydrogenation reactions progressively organize ordered graphite structures. Vlasov and Warnatz (2002) propose a competitive role for the polyyne molecules as important soot precursors. The polyyne pathway is derived from the works of Krestinin (2000) and assumes that these species grow rapidly with successive additions of C2H radicals... 

Their model was based on estimates of the thermodynamic properties, and their experimental results agreed well with the model of a C2H radical. Later, Baddour and Iwasyk (13) and Baddour and Blanchet (14) also invoked the C2H mechanism to explain their results of reacting hydrogen with carbon in a consumable anode arc reactor. 

As with methane, the photolysis of acetylene and subsequent chemistry involving the ethynyl (C2H) radical plays an important role in establishing the hydrocarbon balance in the atmospheres of the outer planets and their moons [4, 311]. The ethynyl radical is also an important reactive intermediate in combustion processes both it and acetylene have been implicated in soot formation, as well as in some models of diamond growth by chemical vapor deposition methods. 

Chastaing D, James PL, Sims IR, Smith IWM. (1998) Neutral-neutral reactions at the temperatnres of interstellar clouds - Rate coefhcients for reactions of C2H radicals with O2, C2H2, C2H4 and CsHe down to 15K. Famday Discuss 109 165-181 Vakhtin AB, Heard DE, Smith IWM, Leone SR. (2001) Kinetics of C2H radical reactions with ethene, propene and 1-butene measured in a pulsed Laval nozzle apparatus at T=103 and 296 K. Chem. Phys. Lett. 348 21-26. 

Vakhtin AB, Heard DE, Smith IWM, Leone SR. (2001) Kinetics of C2H radical reactions with ethene propene and 1-butene measured in a pulsed Laval nozzle apparatus at T = 103 and 296 K. Chem. Phys. Lett 348 21-26. 

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