Formation of C6HnSi+ (n = 5–8) from phenylsilane: an experimental and theoretical study

2011

The potential energy surface (PES) for the loss of HCN or HNC from the pyrazine molecular ion was determined based on quantum chemical calculations using the G3//B3LYP method. Four possible dissociation pathways to form four C3H3N +• isomers were examined. A Rice-Ramsperger-Kassel-Marcus quasi-equilibrium theory model calculation was performed to predict the dissociation rate constant and the product branching ratio on the basis of the obtained PES. The resultant rate constant for the HCN loss agreed with the previous experimental result. The kinetic analysis predicted that the formation of CH=CHN ≡ CH +• + HCN was predominant, which occurred by three consecutive steps, a C-C bond cleavage to form a linear intermediate, a rearrangement to form an H-bridged intermediate, and elimination of HCN.

Section: Introductionmentioning

confidence: 99%

Loss of HCN from the Pyrazine Molecular Ion: A Theoretical Study

Yim¹,

2011

“…In the dissociations of toluene and aniline molecular ions, 3,4 these isomers contribute to the loss of H•, whereas for the phenylphosphine and thiophenol molecular ions, 7,8 these isomers undergo a ring contraction to five-membered ring isomers followed by the elimination of HCP and C2H2, respectively. Loss of H2 is an important dissociation channel in the dissociation of phenylsilane, 6 phenylphosphine, 7 or phenylarsane 9,10 molecular ions, but this loss is not observed in the toluene 3 or aniline 4 molecular ions. This difference is mainly due to the more extended and diffuse nature of the outermost p orbitals of Si, P, and As.…”

Section: Introductionmentioning

confidence: 98%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Their reaction kinetics has often been understood by exploring the potential energy surfaces for the isomerizations and the dissociations. Ionized benzene derivatives are among the most interesting subjects to gas phase ion chemists.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the isomerization and dissociation mechanisms of some ionized monosubstituted benzenes, C6H5XHn +• (X = C, N, O, Si, P, S, and As), have been proposed using quantum chemical calculations. [2][3][4][5][6][7][8][9][10] Both similarities and differences were found among their dissociation mechanisms. Ring expansion to seven-membered ring isomers is a common mechanism for theses molecular ions.…”

Section: Introductionmentioning

confidence: 99%

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Dissociation of the Phenylarsane Molecular Ion: A Theoretical Study

Kim¹,

2010

The potential energy surfaces (PESs) for the primary and secondary dissociations of the phenylarsane molecular ion (1a) were determined from the quantum chemical calculations using the G3(MP2)//B3LYP method. Several pathways for the loss of H• were determined and occurred though rearrangements as well as through direct bond cleavages. The kinetic analysis based on the PES for the primary dissociation showed that the loss of H2 was more favored than the loss of H•, but the H• loss competed with the H2 loss at high energies. The bicyclic isomer, 7-arsa-norcaradiene radical cation, was formed through the 1,2 shift of an α-H of 1a and played an important role as an intermediate for the further rearrangements in the loss of H• and the losses of As• and AsH. The reaction pathways for the formation of the major products in the secondary dissociations of [M-H] + and [M-H2] +• were examined. The theoretical prediction explained the previous experimental results for the dissociation at high energies but not the dissociation at low energies.

“…Similar six to seven-membered ring expansions of radical cations of toluene analogues and its derivatives, such as phenylsilane, 3 anilne (AN), 4 methylpyridines (picolines, MPs), 5 phenylphosphine, 6 phenylarsane, 7 phenol, 8 thiophenol, 9 and halotoluenes [10][11][12][13][14][15] have been investigated to understand their dissociation mechanisms. Several theoretical studies showed that ring contractions to five-membered intermediates played important roles in the dissociations of those cations, including the N, O, and P atoms.…”

Section: Introductionmentioning

confidence: 99%

Does the Gaseous Aniline Cation Isomerize to Methylpyridine Cations Before Dissociation?

2013

Self Cite

We have explored the potential energy surface for the isomerization of the aniline (AN) radical cation to the 2-, 3-, and 4-methylpyridine (picoline, MP) radical cations using G3 model calculations. The isomerization may occur through the 1H-azepine (7-aza-cycloheptatriene) radical cation. A quantitative kinetic analysis has been performed using the Rice-Ramsperger-Kassel-Marcus theory, based on the potential energy surface. The result shows that isomerization between AN +• and each MP +• hardly occurs before their dissociations.