The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Bogdan Z. Dlugogorski - One of the best experts on this subject based on the ideXlab platform.
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Inhibition and Promotion of Pyrolysis by Hydrogen Sulfide (H2S) and Sulfanyl Radical (SH).
Journal of Physical Chemistry A, 2016Co-Authors: Zhe Zeng, Ibukun Oluwoye, Mohammednoor Altarawneh, Peter Glarborg, Bogdan Z. DlugogorskiAbstract:This study resolves the interaction of sulfanyl radical (SH) with aliphatic (C1–C4) hydrocarbons, using CBS-QB3 based calculations. We obtained the C–H dissociation enthalpies and located the weakest link in each hydrocarbon. Subsequent computations revealed that, H abstraction by SH from the weakest C–H sites in Alkenes and alkynes, except for ethylene, appears noticeably exothermic. Furthermore, abstraction of H from propene, 1-butene, and iso-butene displays pronounced spontaneity (i.e., ΔrG° < −20 kJ mol–1 between 300–1200 K) due to the relatively weak allylic hydrogen bond. However, an alkyl radical readily abstracts H atom from H2S, with H2S acting as a potent scavenger for alkyl radicals in combustion processes. That is, these reactions proceed in the opposite direction than those involving SH and alkene or alkyne species, exhibiting shallow barriers and strong spontaneity. Our findings demonstrate that the documented inhibition effect of hydrogen sulfide (H2S) on pyrolysis of alkanes does not appl...
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Inhibition and promotion of pyrolysis by hydrogen sulfide (H2S) and sulfanyl radical (SH)
Journal of Physical Chemistry A, 2016Co-Authors: Zhe Zeng, Ibukun Oluwoye, Mohammednoor Altarawneh, Peter Glarborg, Bogdan Z. DlugogorskiAbstract:© 2016 American Chemical Society. This study resolves the interaction of sulfanyl radical (SH) with aliphatic (C 1 -C 4 ) hydrocarbons, using CBS-QB3 based calculations. We obtained the C-H dissociation enthalpies and located the weakest link in each hydrocarbon. Subsequent computations revealed that, H abstraction by SH from the weakest C-H sites in Alkenes and alkynes, except for ethylene, appears noticeably exothermic. Furthermore, abstraction of H from propene, 1-butene, and iso-butene displays pronounced spontaneity (i.e., Δ r G° < -20 kJ mol -1 between 300-1200 K) due to the relatively weak allylic hydrogen bond. However, an alkyl radical readily abstracts H atom from H 2 S, with H 2 S acting as a potent scavenger for alkyl radicals in combustion processes. That is, these reactions proceed in the opposite direction than those involving SH and alkene or alkyne species, exhibiting shallow barriers and strong spontaneity. Our findings demonstrate that the documented inhibition effect of hydrogen sulfide (H 2 S) on pyrolysis of alkanes does not apply to Alkenes and alkynes. During interaction with hydrocarbons, the inhibitive effect of H 2 S and promoting interaction of SH radical depend on the reversibility of the H abstraction processes. For the three groups of hydrocarbon, Evans-Polanyi plots display linear correlations between the bond dissociation enthalpies of the abstracted hydrogens and the relevant activation energies. In the case of methane, we demonstrated that the reactivity of SH radicals toward abstracting H atoms exceeds that of HO 2 but falls below those of OH and NH 2 radicals. (Figure Presented).
Midori Goto - One of the best experts on this subject based on the ideXlab platform.
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facile regio and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes selective hydrogenation of alkynes with formic acid
ChemInform, 2012Co-Authors: Ruwei Shen, Xiangbo Wang, Yongbo Zhou, Tieqiao Chen, Yalei Zhao, Midori GotoAbstract:The catalytic hydrogenation of alkynes such as (I) with formic acid can be controlled by changing the conditions to selectively produce (Z)-Alkenes such as (II), (E)-Alkenes such as (III), or alkanes such as (IV).
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facile regio and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes selective hydrogenation of alkynes with formic acid
Journal of the American Chemical Society, 2011Co-Authors: Ruwei Shen, Xiangbo Wang, Yongbo Zhou, Tieqiao Chen, Yalei Zhao, Midori GotoAbstract:A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt3)4 (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt3)4, but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brϕnsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-Alkenes and alkanes by slightly tuning the conditions.
Zhe Zeng - One of the best experts on this subject based on the ideXlab platform.
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Inhibition and Promotion of Pyrolysis by Hydrogen Sulfide (H2S) and Sulfanyl Radical (SH).
Journal of Physical Chemistry A, 2016Co-Authors: Zhe Zeng, Ibukun Oluwoye, Mohammednoor Altarawneh, Peter Glarborg, Bogdan Z. DlugogorskiAbstract:This study resolves the interaction of sulfanyl radical (SH) with aliphatic (C1–C4) hydrocarbons, using CBS-QB3 based calculations. We obtained the C–H dissociation enthalpies and located the weakest link in each hydrocarbon. Subsequent computations revealed that, H abstraction by SH from the weakest C–H sites in Alkenes and alkynes, except for ethylene, appears noticeably exothermic. Furthermore, abstraction of H from propene, 1-butene, and iso-butene displays pronounced spontaneity (i.e., ΔrG° < −20 kJ mol–1 between 300–1200 K) due to the relatively weak allylic hydrogen bond. However, an alkyl radical readily abstracts H atom from H2S, with H2S acting as a potent scavenger for alkyl radicals in combustion processes. That is, these reactions proceed in the opposite direction than those involving SH and alkene or alkyne species, exhibiting shallow barriers and strong spontaneity. Our findings demonstrate that the documented inhibition effect of hydrogen sulfide (H2S) on pyrolysis of alkanes does not appl...
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Inhibition and promotion of pyrolysis by hydrogen sulfide (H2S) and sulfanyl radical (SH)
Journal of Physical Chemistry A, 2016Co-Authors: Zhe Zeng, Ibukun Oluwoye, Mohammednoor Altarawneh, Peter Glarborg, Bogdan Z. DlugogorskiAbstract:© 2016 American Chemical Society. This study resolves the interaction of sulfanyl radical (SH) with aliphatic (C 1 -C 4 ) hydrocarbons, using CBS-QB3 based calculations. We obtained the C-H dissociation enthalpies and located the weakest link in each hydrocarbon. Subsequent computations revealed that, H abstraction by SH from the weakest C-H sites in Alkenes and alkynes, except for ethylene, appears noticeably exothermic. Furthermore, abstraction of H from propene, 1-butene, and iso-butene displays pronounced spontaneity (i.e., Δ r G° < -20 kJ mol -1 between 300-1200 K) due to the relatively weak allylic hydrogen bond. However, an alkyl radical readily abstracts H atom from H 2 S, with H 2 S acting as a potent scavenger for alkyl radicals in combustion processes. That is, these reactions proceed in the opposite direction than those involving SH and alkene or alkyne species, exhibiting shallow barriers and strong spontaneity. Our findings demonstrate that the documented inhibition effect of hydrogen sulfide (H 2 S) on pyrolysis of alkanes does not apply to Alkenes and alkynes. During interaction with hydrocarbons, the inhibitive effect of H 2 S and promoting interaction of SH radical depend on the reversibility of the H abstraction processes. For the three groups of hydrocarbon, Evans-Polanyi plots display linear correlations between the bond dissociation enthalpies of the abstracted hydrogens and the relevant activation energies. In the case of methane, we demonstrated that the reactivity of SH radicals toward abstracting H atoms exceeds that of HO 2 but falls below those of OH and NH 2 radicals. (Figure Presented).
John E Bercaw - One of the best experts on this subject based on the ideXlab platform.
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upgrading light hydrocarbons via tandem catalysis a dual homogeneous ta ir system for alkane alkene coupling
Journal of the American Chemical Society, 2013Co-Authors: David C Leitch, Jay A Labinger, John E BercawAbstract:Light alkanes and Alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and Alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl_2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C_(13)/C_(14) products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H_2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta).
Akiya Ogawa - One of the best experts on this subject based on the ideXlab platform.
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synthesis of selenium compounds by free radical addition based on visible light activated se se bond cleavage
Mini-reviews in Medicinal Chemistry, 2013Co-Authors: Akihiro Nomoto, Yohsuke Kobiki, Yoshihiro Higuchi, Akiya OgawaAbstract:Upon irradiation with near-UV or visible light, organic diselenides undergo homolytic cleavage of their selenium-selenium linkage to generate the corresponding seleno radicals, which can add to alkynes, allenes, and related unsaturated compounds. In the case of alkynes, vicinally diselenated Alkenes are synthesized successfully. Photoinduced bisselenation of allenes takes place selectively at the terminal double bond of allenes. In sharp contrast, photoinduced addition of organic diselenides to Alkenes is an inefficient process. However, combination of diselenides and disulfides under photoirradiation conditions results in highly regioselective thioselenation of Alkenes based on the higher reactivity of thio radicals toward Alkenes and the higher carbon radical capturing ability of diselenides. Similar conditions can be employed with a variety of unsaturated compounds such as alkynes, allenes, conjugated dienes, vinylcyclopropanes, and isocyanides. This protocol can also be applied to selenotelluration, selenophosphination, and perfluoroalkylselenation of unsaturated compounds. The excellent carbon radical capturing ability of diselenides makes it possible to attain sequential addition of diselenides to several unsaturated compounds by suppression of polymerization of unsaturated compounds. When the sequential addition takes place intramolecularly under photoirradiation conditions, cyclic products are obtained successfully via a radical cyclization process. In addition, novel photoinduced electrocyclic reaction of o-alkynylaryl isocyanides with diselenides efficiently affords diselenated quinoline derivatives.
