The face-centred ? complex isomer of the benzenium ion is probably the most stable form in the gas phase: experimental evidence

Mason, Rod S.; Williams, Christopher M; Anderson, Peter D. J.

doi:10.1039/c39950001027

Cited by 32 publications

(26 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[33][34][35], MS [36], and theoretical calculations [31,33,34,37] have indicated a planar (C 2v ) complex structure in which the extra hydrogen (to the benzene structure) is -bonded to a carbon. While there is a consensus on the complex being the most stable structure, Mason et al [38] and Dewar [39] have proposed a complex between hydrogen and the system of the benzene ring. In the latter, it is argued that any other structure would not be aromatic and would suffer a significant decrease in resonance energy.…”

Section: Resultsmentioning

confidence: 99%

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

Hejazi

Ebrahimi

Guilhaus

et al. 2009

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

There is a consensus that electron impact ionization mass spectrometry is not capable of discriminating among geometrical isomers of unsaturated fatty acid methyl esters (and in general olefinic compounds). In this paper, we report the identification of all eight geometrical isomers of ␣-linolenic acid, one of the few essential -3 fatty acids that has attracted great attention, using low-energy electron ionization mass spectrometry. Three electron energies 70, 50, and 30 eV were studied and the mass spectrum of each isomer was obtained from the analysis of different concentrations of a standard mixture of ␣-linolenic acid methyl ester geometrical isomers to ensure the robustness of the method. Principal component analysis was employed to model the complex variation of m/z intensities across the isomers. Only using the data of 30 eV energy was complete differentiation among geometrical isomers observed. The unique cleavage pattern of the ␣-linolenic acid methyl ester isomers leading to a benzenium ion structure is discussed and general fragmentation rules are derived using the mass spectra of over 300 compounds with different kinds and levels of unsaturation. Application of the proposed method is not limited to ␣-linolenic acid. It can potentially be used to identify the geometrical isomers of any compounds with an olefinic chain. (J Am Soc Mass Spectrom 2009, 20, 1272-1280

show abstract

Section: Resultsmentioning

confidence: 99%

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

Hejazi

Ebrahimi

Guilhaus

et al. 2009

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…[9][10][11][12] Quantumchemical computations also support this assignment and predict that the bridged π -complex (2) is a transition state for a 1,2-H shift within (1) and that the face-centered π complex (3) is a second-order saddle point. 13,14 Early low resolution UV (Refs. 15 and 16) and infrared (IR) (Refs.…”

Section: Introductionmentioning

confidence: 99%

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen

Bahou

Lee

2012

The Journal of Chemical Physics

View full text Add to dashboard Cite

We use protonated benzene (C(6)H(7)(+)) and cyclohexadienyl radical (c-C(6)H(7)) to demonstrate a new method that has some advantages over other methods currently used. C(6)H(7)(+) and c-C(6)H(7) were produced on electron bombardment of a mixture of benzene (C(6)H(6)) and para-hydrogen during deposition onto a target at 3.2 K. Infrared (IR) absorption lines of C(6)H(7)(+) decreased in intensity when the matrix was irradiated at 365 nm or maintained in the dark for an extended period, whereas those of c-C(6)H(7) increased in intensity. Observed vibrational wavenumbers, relative IR intensities, and deuterium isotopic shifts agree with those predicted theoretically. This method, providing a wide spectral coverage with narrow lines and accurate relative IR intensities, can be applied to larger protonated polyaromatic hydrocarbons and their neutral species which are difficult to study with other methods.

show abstract

“…10 In addition, Reed et al 11 reported the crystallization of 1 with carboranes as counterions; they analyzed properties such as its thermal stability, NMR spectra, X-ray structure and carried out theoretical calculations for comparison with structural data. Information on the dehydrogenation process of 1 was obtained by Mason et al 12 from collision-induced decomposition experiments. These authors discussed the stability of this cation and suggested that the p complex, the one in which the H atom lies on top of the aromatic ring, has a relevant role in the mechanism as the stable intermediate.…”

Section: Introductionmentioning

confidence: 99%

Energetic and electron density analysis of hydrogen dissociation of protonated benzene

García‐Revilla

Hernández‐Trujillo

2009

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The electronic structure of the benzenium cation, [C6H7]+, the simplest intermediate of electrophilic aromatic substitution reactions, was analyzed in terms of the properties of electron densities obtained from multiconfigurational quantum theoretical methods. The indirect C-H coupling constants and the physical contributions to their values were calculated and rationalized in terms of the electron delocalization between the quantum topological atoms in the molecule. The evolution of the electronic structure for the intramolecular proton migration and for the dissociation into [C6H6]+ + H, or [C6H5]+ + H2 was also studied. The potential energy surface for intramolecular H migration has six equivalent transition states and two equivalent two-fold saddles, whereas each dissociation process occurs without the presence of any transition state. The calculated energy barriers of 9.5, 80.3 and 72.4 kcal mol(-1) for the intramolecular proton migration, H and H2 eliminations, respectively, agree with experimental reports. The quantitative chemical descriptors based on the electron density of the benzenium cation provide insight on the nature of the chemical bond, including electron delocalization, and its evolution during chemical transformations of the molecule.

show abstract

The face-centred ? complex isomer of the benzenium ion is probably the most stable form in the gas phase: experimental evidence

Cited by 32 publications

References 12 publications

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen

Energetic and electron density analysis of hydrogen dissociation of protonated benzene

Contact Info

Product

Resources

About