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1,055 results on '"bond dissociation energy"'

205. Spectroscopic evidence of α,α-dimethylbenzyl radicals in the gas phase.

Author

Chae, Sang Youl, Lim, Manho, and Lee, Sang Kuk

Subjects
*BENZYL alcohol, *RADICALS (Chemistry), *GAS phase reactions, *CUMENE, *DISSOCIATION (Chemistry)
Abstract

We report the spectroscopic evidence of the jet-cooled α,α-dimethylbenzyl radical, which was generated in a technique of corona excited supersonic expansion using a pinhole-type glass nozzle. For identification of the α,α-dimethylbenzyl radical, precursors that form a common molecular radical, as a result of dissociation of either a C H bond or C C bond of alkyl group in a corona discharge, were employed. Based on comparisons of the spectra observed from the corona discharges of isopropylbenzene and tert -butylbenzene, evidence was obtained of the existence of the α,α-dimethylbenzyl radical in the gas phase. [ABSTRACT FROM AUTHOR]

Published
2016
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208. Displacement of Cl substituent in chlorofluorotoluene in corona discharge.

Author

Chae, Sang Youl, Lim, Manho, and Lee, Sang Kuk

Subjects
*CHLORIDES, *SUBSTITUENTS (Chemistry), *TOLUENE, *AROMATIC compound derivatives, *ELECTRIC discharges, *METHYL groups, *CHEMICAL precursors
Abstract

The precursor 2-chloro-6-fluorotoluene can produce the 2-chloro-6-fluorobenzyl radical in corona discharge, together with the 2-fluorobenzyl radical which could be generated by the displacement of Cl with H of methyl group. In order to identify the reaction mechanism, two precursors, 2-chloro-6-fluorotoluene and 2-chloro-6-fluorobenzyl chloride were employed to observe the vibronic emission spectra from the corona discharge with a large amount of inert carrier gas He. By comparing the spectra observed, we are able to propose the displacement mechanism of Cl, in which methyl group is believed to play an important role in the process, which is discussed in terms of bond dissociation energies. [ABSTRACT FROM AUTHOR]

Published
2016
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218. Energy Constants of Molecules

Author

Khristenko, Sergei V., Shevelko, Viatcheslav P., Maslov, Alexander I., Ecker, Günter, editor, Lambropoulos, Peter, editor, Sobel’man, Igor I., editor, Walther, Herbert, editor, Lotsch, Helmut K. V., editor, Khristenko, Sergei V., Shevelko, Viatcheslav P., and Maslov, Alexander I.

Published
1998
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219. Thermal Analysis of Plastics Used in the Food Industry

Author

Małgorzata Majder-Łopatka, Tomasz Węsierski, Artur Ankowski, Kamil Ratajczak, Dominik Duralski, Aleksandra Piechota-Polanczyk, and Andrzej Polanczyk

Subjects
Technology, Microscopy, QC120-168.85, polypropylene (PP), bond dissociation energy, QH201-278.5, polystyrene (PS), Engineering (General). Civil engineering (General), Article, TK1-9971, differential scanning calorimetry, thermogravimetric, thermal decomposition, polyethylene terephthalate (PET), Descriptive and experimental mechanics, General Materials Science, Electrical engineering. Electronics. Nuclear engineering, TA1-2040
Abstract

Fires in landfills, where used plastic packaging waste is discarded, have shown how great a fire hazard these types of materials pose. In this study, the course of thermo-oxidation of samples made of polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) based plastics was determined. Based on an analysis of the dissociation energy of bonds between atoms in a polymer molecule, the mechanisms responsible for the character and course of degradation were observed. It was found that the degradation rate of PP and PS could be a result of the stability of C-H bonds on the tertiary carbon atom. In the case of PS, due to facilitated intramolecular hydrogen transfer, stabilization of hydroperoxide, and formation of a stable tertiary alcohol molecule, the onset of degradation is shifted towards higher temperatures than in the case of PP. Notably, the PP fragmentation occurs to a greater extent due to the easier course of β-scission. In addition, it was found that during a fire, the least amount of heat would be generated by thermo-oxidation of PS-based plastics. This is a result of the formation of a styrene molecule during decomposition that, due to the high stability of bonds in the aromatic ring, escapes from the combustion zone without oxidation. It has been proven that the greatest thermal effect accompanies PET decomposition, during which a phenyl radical is produced, where the C-H bonds break more easily in comparison with the bonds of an intact ring.

Published
2021
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229. Electronic Models for Cytochrome P450 Oxidations

Author

Korzekwa, Kenneth R., Grogan, James, DeVito, Steven, Jones, Jeffrey P., Snyder, Robert, editor, Sipes, I. Glenn, editor, Jollow, David J., editor, Monks, Terrence J., editor, Kocsis, James J., editor, Kalf, George F., editor, Greim, Helmut, editor, and Witmer, Charlotte M., editor

Published
1996
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235. The Reactions of Na2 with O2

Author

Hou, H., Lu, K-T., Sadchenko, V., Suits, A. G., Lee, Y. T., Goidanskii, Vitalii I., editor, Schäfer, Fritz Peter, editor, Toennies, J. Peter, editor, Lotsch, Helmut K. V., editor, Wolfrum, J., editor, Volpp, H.-R., editor, Rannacher, R., editor, and Warnatz, J., editor

Published
1996
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242. Oxidation of Alkanes

Author

Shilov, A. E., Karasevich, E. I., Ugo, R., editor, James, B. R., editor, Montanari, Fernando, editor, and Casella, Luigi, editor

Published
1994
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244. Assessment

Author

Fliszár, Sándor, Berthier, Gaston, editor, Dewar, Michael J. S., editor, Fischer, Hanns, editor, Fukui, Kenichi, editor, Hall, George G., editor, Hinze, Jürgen, editor, Jortner, Joshua, editor, Kutzelnigg, Werner, editor, Ruedenberg, Klaus, editor, Tomasi, Jacopo, editor, and Fliszár, Sándor

Published
1994
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245. Bond Dissociation Energies

Author

Fliszár, Sándor, Berthier, Gaston, editor, Dewar, Michael J. S., editor, Fischer, Hanns, editor, Fukui, Kenichi, editor, Hall, George G., editor, Hinze, Jürgen, editor, Jortner, Joshua, editor, Kutzelnigg, Werner, editor, Ruedenberg, Klaus, editor, Tomasi, Jacopo, editor, and Fliszár, Sándor

Published
1994
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246. The Valence Region of Molecules

Author

Fliszár, Sándor, Berthier, Gaston, editor, Dewar, Michael J. S., editor, Fischer, Hanns, editor, Fukui, Kenichi, editor, Hall, George G., editor, Hinze, Jürgen, editor, Jortner, Joshua, editor, Kutzelnigg, Werner, editor, Ruedenberg, Klaus, editor, Tomasi, Jacopo, editor, and Fliszár, Sándor

Published
1994
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247. The Chemical Bond

Author

Fliszár, Sándor, Berthier, Gaston, editor, Dewar, Michael J. S., editor, Fischer, Hanns, editor, Fukui, Kenichi, editor, Hall, George G., editor, Hinze, Jürgen, editor, Jortner, Joshua, editor, Kutzelnigg, Werner, editor, Ruedenberg, Klaus, editor, Tomasi, Jacopo, editor, and Fliszár, Sándor

Published
1994
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250. Theoretical speculation on the chemical reaction activity site and degradation mechanism of chloramphenicol.

Author

Wang, Honglei, Dong, Wenbo, and Shi, Jin

Subjects
*CHEMICAL reactions, *CHLORAMPHENICOL, *DENSITY functional theory, *CHARGE exchange, *SPECULATION
Abstract

Three possible reaction pathways. [Display omitted] • Explanation on reactivity center of B(C1 C2) and no N -related products is provided. • Three atomic sites, O28, O30 and N5, are the most possible nucleophilic sites. • N5 is the most favourable site with electrostatic control. Chemical reaction active sites of chloramphenicol are investigated by density functional theory. Three atomic sites are considered the most possible nucleophilic sites. Results indicate that the chemical reaction active sites are formed around four bond sites associated with three nucleophilic atom sites. CAP is a case of joint electrostatic and electron transfer control, and N5 is the most favourable site with electrostatic control, while the reaction between CAP and free radical is transfer control. Moreover, a detailed explanation on why bond (C1 C2) is considered the reactivity center of CAP and why no N -related products are generated in experiments is provided. [ABSTRACT FROM AUTHOR]

Published
2023
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