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Alkenes

The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Bogdan Z. Dlugogorski – 1st expert on this subject based on the ideXlab platform

  • Inhibition and Promotion of Pyrolysis by Hydrogen Sulfide (H2S) and Sulfanyl Radical (SH).
    Journal of Physical Chemistry A, 2016
    Co-Authors: Zhe Zeng, Mohammednoor Altarawneh, Ibukun Oluwoye, Peter Glarborg, Bogdan Z. Dlugogorski

    Abstract:

    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...

  • Inhibition and promotion of pyrolysis by hydrogen sulfide (H2S) and sulfanyl radical (SH)
    Journal of Physical Chemistry A, 2016
    Co-Authors: Zhe Zeng, Mohammednoor Altarawneh, Ibukun Oluwoye, Peter Glarborg, Bogdan Z. Dlugogorski

    Abstract:

    © 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 – 2nd expert on this subject based on the ideXlab platform

  • 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, 2012
    Co-Authors: Ruwei Shen, Tieqiao Chen, Yalei Zhao, Yongbo Zhou, Xiangbo Wang, Midori Goto

    Abstract:

    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).

  • 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, 2011
    Co-Authors: Ruwei Shen, Tieqiao Chen, Yalei Zhao, Yongbo Zhou, Xiangbo Wang, Midori Goto

    Abstract:

    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 – 3rd expert on this subject based on the ideXlab platform

  • Inhibition and Promotion of Pyrolysis by Hydrogen Sulfide (H2S) and Sulfanyl Radical (SH).
    Journal of Physical Chemistry A, 2016
    Co-Authors: Zhe Zeng, Mohammednoor Altarawneh, Ibukun Oluwoye, Peter Glarborg, Bogdan Z. Dlugogorski

    Abstract:

    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...

  • Inhibition and promotion of pyrolysis by hydrogen sulfide (H2S) and sulfanyl radical (SH)
    Journal of Physical Chemistry A, 2016
    Co-Authors: Zhe Zeng, Mohammednoor Altarawneh, Ibukun Oluwoye, Peter Glarborg, Bogdan Z. Dlugogorski

    Abstract:

    © 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).