Comment on:  “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Speranza, Maurizio

doi:10.1021/jp011909m

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…When the silyl group is drawn closer to a positive charge center in the meta-isomer ( 2 ) and ortho-isomer ( 3 ), not only the ring structure destorts from the symmetry of phenylsilane but also the positive charge character shifts from the ring to silicon. Consequently, the barrier height of the ring hydride shift ( TS1 and TS2 ) decreases slightly, although they do not differ substantially from the corresponding value in the phenyl cation (compare MP2 values in Table with the value of 40.1 kcal/mol for the barrier in the phenyl cation). The deformation energy, i.e., the energy of geometry relaxation from the nascent nucleogenic ion structure (phenylsilane structure in our case) to the equilibrium structure of the ion, calculated as a difference between total energies of a cation in these two structures, is 34.0 and 39.4 kcal/mol for the o- silatolyl cation at the B3LYP and MP2 levels, respectively.…”

Section: Resultsmentioning

confidence: 92%

“…Interconversions between the tolyl isomers may occur through hydride shift. Classical barrier heights for hydride shift as well as for this isomerization of nucleogenic phenyl and tolyl cations were subjects of previous works. − Experimentalists presume that hydride shifts may occur in free phenyl cations, − , to the contrary, theory ,, predicts that the intrinsic potential internal energy of the nascent nucleogenic ion is not high enough to overcome the barrier for these shifts.…”

Section: Introductionmentioning

confidence: 99%

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Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study

et al. 2009

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Nucleogenic cations were formed by beta-decay of phenylsilane tritiated at ortho- and para-positions of the benzene ring as well as at the silyl group and the products of their reactions with methyl tert-butyl ether were analyzed by radiochromatography. We found that the o-silatolyl cation was isomerized into the silabenzyl cation while the p-silatolyl cation was not. Furthermore, the silabenzyl cation was not converted into other isomers. The potential energy surface of the C(6)H(7)Si(+) system was constructed by B3LYP and MP2 methods using an aug-cc-pVDZ basis set. Theory predicts the low barrier for o-silatolyl-silabenzyl isomerization but high barriers for hydride shifts in the ring from para to meta- to ortho-isomers. It seems that nascent nucleogenic ions have enough internal energy to overcome the ortho-to-benzyl barrier but not enough to cross over the hydride-shift barriers. Theory also confirms that the isomerization of the silabenzyl cation to the [C(6)H(6).SiH](+) complex takes place in one step with a 62 kcal mol(-1) barrier, whereas that to either the global minimum [C(6)H(7).Si](+) or the silatropylium ion involves multisteps with 69-80 kcal/mol barriers. In addition, we find that the barrier of interconversion between the [C(6)H(6).SiH](+) complex and one of the low-lying [C(6)H(7).Si](+) complexes is only 29 kcal/mol.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study

et al. 2009

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“…This was the first estimate of these values (which included geometry optimization) with the help of the correlated methods. However, Speranza argued that the B3LYP method is too inaccurate and repeated his previous statement that more refined calculations may reduce the − E def difference to zero or negative values. Since B3LYP usually gives thermochemical parameters accurate within several kilocalories per mole, it is difficult to believe that the 15 kcal/mol difference may disappear at higher levels of theory, especially if one takes into account the well-known propensity of B3LYP to underestimate the barrier heights. − …”

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confidence: 96%

Reply to Comment on “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Ignatyev

Sundius

2002

J. Phys. Chem. A

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Phenylium ion automerization was revealed in the radiochromatographic study of reactions between nucleogenic cations and CH 3 X (X ) OH, F, Cl, Br). [1][2][3] However, the possibility of automerization was called in question by the results of theoretical studies 4-6 which predicted large barriers to 1,2-hydrogen shift. Nucleogenic cations formed by tritium decay may possess excess energy due to the fact that their nascent geometry is that of their neutral precursors. 7 Relaxation of their geometry to the equilibrium may release energy which makes the ion vibrationally excited. This excess energy (E def ) may allow the phenyl cation to overcome the 1,2-hydrogen shift barrier (E isomer

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Mass Spectrometry and Gas‐Phase Ion Chemistry of Hypervalent Halogen Compounds

O’Hair

2018

Patai's Chemistry of Functional Groups

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Studies relevant to the gas‐phase formation, reactions, structure, thermochemistry, kinetics, and mass spectrometry of hypovalent halogen compounds are reviewed. The types of species considered include two‐center–three‐electron bond dimer radical cations of methyl halides; aliphatic, aromatic, and cyclic halonium ions; charged iodonium compounds; neutral iodonium compounds and their reaction products with organic substrates; iodosobenzene and its analogs and their adducts with transition metal complexes; and other oxides of halides. These studies highlight the broad scientific interest in the interaction of hypovalent halogen compounds, which span the range from traditional organic and organometallic chemistry, catalysis through to the development of methods for proteomics.

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Comment on: “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Cited by 3 publications

References 14 publications

Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study

Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study

Reply to Comment on “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Mass Spectrometry and Gas‐Phase Ion Chemistry of Hypervalent Halogen Compounds

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Comment on: “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Cited by 3 publications

References 14 publications

Rearrangements of [C6H7Si]+ Cations. A Radiochemical and Quantum Chemical Study

Rearrangements of [C6H7Si]+ Cations. A Radiochemical and Quantum Chemical Study

Reply to Comment on “Reactions of Phenyl Cations with Methanol and Methyl Fluoride”

Mass Spectrometry and Gas‐Phase Ion Chemistry of Hypervalent Halogen Compounds

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Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study

Rearrangements of [C₆H₇Si]⁺ Cations. A Radiochemical and Quantum Chemical Study