Chlorine abstraction by laser pyrolysis of W(CO)6; a mild route to gas-phase organic radical chemistry

Allen, Grant R.; Renner, Noel D.

doi:10.1039/a708737c

Cited by 6 publications

(3 citation statements)

References 14 publications

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“…[19][20][21][22][23][24] We have shown that the technique of infrared laser powered homogeneous pyrolysis (IR LPHP), allied with standard mechanistic tools such as matrix isolation spectroscopies, reaction in the presence of trapping agents, and ab initio or semiempirical calculation of activation energies, can provide unique insights into the mechanisms of pyrolysis in systems as varied as azines, 25 organometallic chemical vapour deposition (CVD) precursors, [26][27][28][29][30][31] glycine 32 and chlorofluorocarbons. 33 In particular, the use of matrix isolation EPR spectroscopy and of radical traps such as H 2 or D 2 allows the disentanglement of molecular and radical pathways. In the case of azines, 25 we have also shown that the use of precursors specifically designed to proceed through relevant radical pathways, principally bromine-substituted analogues, allows even more detailed mechanistic information.…”

Section: Introductionmentioning

confidence: 99%

The thermal decomposition of 5-membered rings: a laser pyrolysis study

Hore

Russell

2004

New J. Chem.

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The mechanisms of pyrolysis of cyclopentadiene, furan, pyrrole and thiophene have been investigated using a combination of IR laser powered homogeneous pyrolysis, chemical and physical trapping of radical intermediates, and use of precursors specifically designed to generate selected radical intermediates. The results confirm the central role played by free radicals in the cases of cyclopentadiene and thiophene, and the dominant step of 1,2-H shifts in the cases of furan and pyrrole. The experimental results may be interpreted according to the high level ab initio calculations recently reported in the literature. NJC

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Section: Introductionmentioning

confidence: 99%

The thermal decomposition of 5-membered rings: a laser pyrolysis study

Hore

Russell

2004

New J. Chem.

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“…A strong signal remains in the range 2200-2100 cm −1 . This species is probably ketene, CH 2 CO, which is known to absorb IR light in that region [27]. Especially the peak at the band center at 2150 cm −1 is typical for ketene.…”

Section: Quantificationmentioning

confidence: 99%

Formation of HNCO, HCN, and NH3 from the pyrolysis of bark and nitrogen-containing model compounds

Hansson

Samuelsson²,

Tullin³

et al. 2004

Combustion and Flame

316

213

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Bark pellets have been pyrolyzed in a fluidized bed reactor at temperatures between 700 and 1000 • C. Identified nitrogen-containing species were hydrogen cyanide (HCN), ammonia (NH 3 ), and isocyanic acid (HNCO). Quantification of HCN and to some extent of NH 3 was unreliable at 700 and 800 • C due to low concentrations. HNCO could not be quantified with any accuracy at any temperature for bark, due to the low concentrations found. Since most of the nitrogen in biomass is bound in proteins, various protein-rich model compounds were pyrolyzed with the aim of finding features that are protein-specific, making conclusions regarding the model compounds applicable for biomass fuels in general. The model compounds used were a whey protein isolate, soya beans, yellow peas, and shea nut meal. The split between HCN and NH 3 depends on the compound and temperature. It was found that the HCN/NH 3 ratio is very sensitive to temperature and increases with increasing temperature for all compounds, including bark. Comparing the ratio for the different compounds at a fixed temperature, the ratio was found to decrease with decreasing release of volatile nitrogen. The temperature dependence implies that heating rate and thereby particle size affect the split between HCN and NH 3 . For whey, soya beans, and yellow peas, HNCO was also quantified. It is suggested that most HCN and HNCO are produced from cracking of cyclic amides formed as primary pyrolysis products. The dependence of the HNCO/HCN ratio on the compound is fairly small, but the temperature dependence of the ratio is substantial, decreasing with increasing temperature. The release of nitrogen-containing species does not seem to be greatly affected by the other constituents of the fuel, and proteins appear to be suitable model compounds for the nitrogen in biomass.

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“…6 It is generally assumed that these products result from the successive homolytic loss of carbonyl groups. We have recently shown that in the presence of vapours of chlorinated organic compounds, 7 the deposits also contain chlorine; XPES and reflectance IR spectroscopy indicate a composition approximating to W(CO) 4 Cl 2 . It appears, therefore, that unsaturated W(CO) n (n < 6) species are highly efficient abstractors of Cl from such compounds.…”

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confidence: 99%