A crossed molecular beams study on the formation and energetics of the resonantly stabilized free i-C4H3(X2A′) radical and its isotopomers

Gu, Xia; Guo, Ying; Zhang, Fangtong; Mebel, Alexander M.; Kaiser, Ralf I.

doi:10.1016/j.chemphys.2007.03.027

Cited by 12 publications

(17 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[137,138] On the singlet surface, the dicarbon molecule is inferred to add without entrance barrier to the carbon-carbon double bond forming a cyclic intermediate i1 (Figure 7 a). The latter undergoes ring-opening via a barrier of only 60 kJ mol À1 to the singlet butatriene intermediate (i2) which decomposes to the i-C 4 H 3 isomer (1-butene-3-ynyl-2) plus atomic hydrogen via a loose exit transition state.…”

Section: The C(mentioning

confidence: 99%

“…The unimolecular decomposition processes of singlet and triplet butatriene molecules (H 2 CCCCH 2 ) were investigated in crossed molecular beams experiments of dicarbon molecules in the X 1 S g + electronic ground state and in the first excited a 3 P u state with ethylene at collision energies between 12.1 and 40.9 kJ mol À1 . [137,138] On the singlet surface, the dicarbon molecule is inferred to add without entrance barrier to the carbon-carbon double bond forming a cyclic intermediate i1 (Figure 7 a). The latter undergoes ring-opening via a barrier of only 60 kJ mol À1 to the singlet butatriene intermediate (i2) which decomposes to the i-C 4 H 3 isomer (1-butene-3-ynyl-2) plus atomic hydrogen via a loose exit transition state.…”

Section: The C 2 a C H T U N G T R E N N U N Gmentioning

confidence: 99%

See 1 more Smart Citation

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Kaiser

Mebel

2008

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

During the last decade, experimental and theoretical studies on the unimolecular decomposition of cumulenes (H(2)C(n)H(2)) from propadiene (H(2)CCCH(2)) to hexapentaene (H(2)CCCCCCH(2)) have received considerable attention due to the importance of these carbon-bearing molecules in combustion flames, chemical vapor deposition processes, atmospheric chemistry, and the chemistry of the interstellar medium. Cumulenes and their substituted counterparts also have significant technical potential as elements for molecular machines (nanomechanics), molecular wires (nano-electronics), nonlinear optics, and molecular sensors. In this review, we present a systematic overview of the stability, formation, and unimolecular decomposition of chemically, photo-chemically, and thermally activated small to medium-sized cumulenes in extreme environments. By concentrating on reactions under gas phase thermal conditions (pyrolysis) and on molecular beam experiments conducted under single-collision conditions (crossed beam and photodissociation studies), a comprehensive picture on the unimolecular decomposition dynamics of cumulenes transpires.

show abstract

Section: The C(mentioning

confidence: 99%

Section: The C 2 a C H T U N G T R E N N U N Gmentioning

confidence: 99%

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Kaiser

Mebel

2008

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

show abstract

“…Estimating accurate thermochemistry of these radicals is clearly of paramount importance. A great deal of computational work has accumulated and suggests that the resonance stabilized i -C 4 H 5 isomers are 23.3–63.6 kJ mol –1 more stable than the n -isomer; − similarly, i -C 4 H 3 isomers are found to be 27.6–50.2 kJ mol –1 more stable than n -C 4 H 3 . − This led to the conclusion that far lower abundances of n -isomers should be observed in flames, which has recently been substantiated with molecular-beam mass spectrometry experiments …”

Section: Introductionmentioning

confidence: 95%

Molecular Mechanisms in the Pyrolysis of Unsaturated Chlorinated Hydrocarbons: Formation of Benzene Rings. 1. Quantum Chemical Studies

McIntosh

Russell

2013

J. Phys. Chem. A

View full text Add to dashboard Cite

Analogues of important aromatic growth mechanisms in hydrocarbon pyrolysis and combustion systems are extended to chlorinated systems. We consider the addition of C2Cl2 to both C4Cl3 and C4Cl5 radicals at the M06-2X/6-311+G(3df,3p)//B3LYP/6-31G(d) level of theory, and we demonstrate that these reaction systems have much in common with those of nonchlorinated species. In particular, we find that these radicals appear to lead preferentially to fulvenes, and not to the observed aromatic products, as is found in nonchlorinated systems. We have therefore also considered nonradical C4/C2 channels by way of Diels-Alder cyclization of C4Cl4/C2Cl2 and C4H2Cl2/C2HCl pairs to describe aromatic formation. While the latter pair readily leads to the formation of partially chlorinated benzenes, the fully chlorinated congeners are sterically prohibited from ring closing directly; this leads to a series of novel rearrangement processes which predict the formation of hexachloro-1,5-diene-3-yne, in addition to hexachlorobenzene, in good agreement with experiment. This suggests, for the first time, that facile nonradical routes to aromatic formation are operative in partially and fully chlorinated pyrolysis and combustion systems.

show abstract

“…C 2 (X 1 ∑ g + /a 3 Π u ) radicals existed more or less in carbon-atom sources produced by laser ablation of graphite and by discharge of CO 2 in the previous experiments. 8,10 The reaction C 2 + C 2 H 4 → C 4 H 3 + H was investigated in crossed molecular beams by Kaiser et al 18 The dissociation of C 4 H 3 to C 3 H 3 + , C 3 H 2 + , C 3 H + , and C 3 + occurred following electron-impact ionization; the daughter ion C 3 H 3 + from reaction C 2 + C 2 H 4 was faster than product C 3 H 3 from reaction C + C 2 H 4 , but no clear feature is able to distinguish both components. 19 The C 2 reaction had a center-of-mass (CM) angle (Θ CM ) smaller than that of the C reaction, which might mislead to a forward-biased angular distribution for product C 3 H 3 .…”

Section: Introductionmentioning

confidence: 99%

Exploring the Dynamics of Reaction C(³P) + C₂H₄ with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations

et al. 2012

View full text Add to dashboard Cite

We investigated the title reaction at collision energy 3.5 kcal mol(-1) in a crossed molecular beam apparatus using undulator radiation as an ionization source. Time-of-flight (TOF) spectra of product C(3)H(3) were measured in laboratory angles from 20° to 100° using two photoionization energies 9.5 and 11.6 eV. These two sets of experimental data exhibit almost the same TOF distributions and laboratory angular distributions. From the best simulation, seven angle-specific kinetic-energy distributions and a nearly isotropic angular distribution are derived for product channel C(3)H(3) + H that has an average kinetic-energy release of 15.5 kcal mol(-1), corresponding to an average internal energy of 33.3 kcal mol(-1) in C(3)H(3). Furthermore, TOF spectra of product C(3)H(3) were measured at laboratory angle 52° with ionizing photon energies from 7 to 12 eV. The appearance of TOF spectra remains almost the same, indicating that a species exclusively contributes to product C(3)H(3); the species is identified as H(2)CCCH (propargyl) based on the ionization energy of 8.6 ± 0.2 eV and the maximal kinetic-energy release of 49 kcal mol(-1). Theoretical calculations indicate that the rapid inversion mechanism and rotation in intermediate H(2)CCCH(2) can result in a forward-backward symmetric angular distribution for product C(3)H(3) + H. The present work avoids the interference of reactions of C((1)D) and C(2) radicals with C(2)H(4) and rules out the probability of production of other isomers like c-C(3)H(3) and H(3)CCC proposed in the previous work at least at the investigated collision energy.

show abstract

A crossed molecular beams study on the formation and energetics of the resonantly stabilized free i-C4H3(X2A′) radical and its isotopomers

Cited by 12 publications

References 28 publications

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Molecular Mechanisms in the Pyrolysis of Unsaturated Chlorinated Hydrocarbons: Formation of Benzene Rings. 1. Quantum Chemical Studies

Exploring the Dynamics of Reaction C(³P) + C₂H₄ with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations

Contact Info

Product

Resources

About

A crossed molecular beams study on the formation and energetics of the resonantly stabilized free i-C4H3(X2A′) radical and its isotopomers

Cited by 12 publications

References 28 publications

Chemistry of Energetically Activated Cumulenes—From Allene (H2CCCH2) to Hexapentaene (H2CCCCCCH2)

Chemistry of Energetically Activated Cumulenes—From Allene (H2CCCH2) to Hexapentaene (H2CCCCCCH2)

Molecular Mechanisms in the Pyrolysis of Unsaturated Chlorinated Hydrocarbons: Formation of Benzene Rings. 1. Quantum Chemical Studies

Exploring the Dynamics of Reaction C(3P) + C2H4 with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations

Contact Info

Product

Resources

About

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Chemistry of Energetically Activated Cumulenes—From Allene (H₂CCCH₂) to Hexapentaene (H₂CCCCCCH₂)

Exploring the Dynamics of Reaction C(³P) + C₂H₄ with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations