Gas to condensed phase transition in hot atom chemistry

Richardson, A.E.; Wolfgang, Richard

doi:10.1021/ja00714a050

Cited by 32 publications

(25 citation statements)

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“…If the interpretation of the reaction mechanism described above is basically correct, some unequivocal correlation must exist between the observed replacement yields and the variable expressed in Eq. (8). Fig.…”

Section: Toymentioning

confidence: 99%

“…This result constituted an important input to the extensive trajectory study [4] which has shown that even the archetype of the impact model reactions, the energetic T-for-H replacement in methane, requires the collusive participation of several atoms of the methane molecule. The special problems arising in the study of reactions of recoil atoms in liquid systems due to differences in moderating parameters [5] and to the autoradiolysis [6,7] and cage recombination [8,9] have been investigated and partly allowed for in a number of experiments. Liquid aromatic systems present additional problems due to the formation of a large amount of polymeric compounds difficult to identify by conventional methods of analysis.…”

Section: Résumémentioning

confidence: 99%

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Reactions of Recoil Fluorine in Liquid Halobenzenes

Berei

Vasaros

1974

Radiochimica Acta

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Experimental investigations of halogen and hydrogen replacements in liquid halobenzenes by nucleogenic fluorine atoms from the le F(n,2n) 18 F process are reported. Liquid binary mixtures of hexafluorobenzene with each of the four monohalobenzenes were irradiated with a 14 MeV neutron generator. The hexafluorobenzene served both as the source of 18 F and as one of the participants in the intermolecular competition reactions. Iodine and bromine were used as scavengers. The products of le F-for-halogen and 18 F-for-hydrogen replacements were identified by gas chromatography. The results are compared with the earlier data on the reactions of hot chlorine, bromine and iodine with aromatic compounds. The 18 F seems to obey the same rules which were found earlier to govern the replacement reactions of the other nucleogenic halogen atoms. The results are discussed in terms of a mechanism which involves a highly inelastic atom-molecule collision and formation of an excited intermediate complex. ZusammenfassungEs wird berichtet über die Verdrängung von Halogen-und WasserstofFatomen durch Radiofluoratome der Reaktion le F(n, 2n) 18 F in flüssigen Halobenzenverbindungen. Binäre Mischungen von Hexafluorobenzen mit jedem der vier Monohalobenzene wurden mit einem 14 MeV Neutronengenerator bestrahlt. Das Hexafluorobenzen bildete sowohl das Ausgangsmaterial für die Bildung des 18 F als einer der Teilnehmer bei den konkurrierenden Reaktionen. Jod und Brom wurden als Radikalfänger verwendet. Die Produkte, worin 18 F an die Stelle eines Waeserstofifatoms oder eines Halogenatoms getreten war, wurden mittels Gaschromatographie nachgewiesen. Die Resultate werden verglichen mit früheren Daten für die Reaktionen von heißem Chlor, Brom und Jod mit aromatischen Verbindungen. Das 18 F scheint denselben Regeln zu folgen, die früher gefunden wurden für die Verdrängungsreaktionen von anderen nukleogenen Halogenatomen. Die Resultate werden besprochen an Hand eines Mechanismus, wobei stark inelastische Atom-Molekülzusammenstöße und die Bildung eines energiereichen intermediären Komplexes eine Rolle spielen.

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Section: Toymentioning

confidence: 99%

Section: Résumémentioning

confidence: 99%

Reactions of Recoil Fluorine in Liquid Halobenzenes

Berei

Vasaros

1974

Radiochimica Acta

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“…In the high pressure and condensed phase enhancement reactions become important. There have been many studies of these multi-molecular reactions throughout the gas to condensed phase transition [26][27][28][29][30][31][32][33], Enhancement reactions appear to be of two types: cage-radical, cage-ion reactions involving semi-random recombinations [26,30] and caged-complex reactions [29,31 ] involving the stabilization of an electronically excited cage complex. Evidence exists that these reactions may occur simultaneously [32,33], Although enhancement reactions are complex and description difficult as a result of the inseparability of enhancement events from molecular reactions, several attempts have been made to develop a semi-emperical description of enhancement events [34][35][36], These have considered the variation of bulk [34] and molecular [35] parameters in photolytically-induced cage radical recombinations and the implantation of a hot atom in a lattice matrix [33], No attempt had been made to simulate the effects of collapsing molecular environment on a chemical system which exhibits enhancement reactions.…”

Section: Condensed Phase Systemsmentioning

confidence: 99%

Computer Simulation Evaluating Kinetic Theory Parameters in Hot Atom Chemistry

Berg

Rack³

1977

Radiochimica Acta

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Computer simulation / Kinetic theory parameters SummaryA computer model using simple kinetic theory parameters has been used to simulate the (n, 7)-activated iodine-128-acetylene system throughout the gas to condensed phase transition. The model was found to be sensitive to molecular size and also to reaction probability functions suggesting the importance of chemical parameters. General agreement was found with experiment and the non-inclusion of an enhancement reaction expression in the model suggests that caged complex reactions may be an extension of simple molecular processes.

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“…The gas to Condensed phase transition technique is an important tool that has been utilized by hot atom chemists to acquire insight into the effects of collapsing molecular environment on the dynamics of high energy chemical processes [8][9][10][11][12][13][14]. The presence of enhancement yields, product yield increases above those expected from extrapolation of low pressure data, can be used with other experimental data in the evaluation of probable product formation routes.…”

mentioning

confidence: 99%

“…Enhancement processes are of two general types: cage-ion or cage-radical reactions, an extension of the FRANCK-RABINOWITSCH "cage-effect" [15] in which a hot atom recombines with ions or radicals of its own creation, and "caged-complex" reactions [10] in which an electronically excited complex is held in spatial configuration by the cage walls for a time sufficient to react. Previous studies have shown that in various hot atom systems, in high pressure and the Condensed phase, product yields can be enhanced to a greater extent than by excitationstabilization of excited products, primarily by cage-ion, cage-radical processes [8,11], "caged-complex" reactions [10,12]oracombinationofboth [13]. Ethane is a low mass, saturated hydrocarbon, providing Experimental Materials.…”

mentioning

confidence: 99%