Elongated (one-electron) carbon-carbon bond in .sigma. and n organic cation radicals

Bellville, Dennis J.; Bauld, Nathan L.

doi:10.1021/ja00385a025

Cited by 45 publications

(29 citation statements)

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“…Radical cation 3 ț + has often been discussed in the literature as to whether it is present as a distonic ring-open species or is connected by a long bond as a cyclobutane radical cation [10,11,25] based on ab initio calculations of distonic and ring-closed radical cations C 4 H 8 ț + by Bauld [26] and Bally [27]. In our investigation the cyclobutane radical cation can be observed exclusively.…”

Section: Esi-ms Investigation Of the [2+2] Cycloaddition Of Trans-anementioning

confidence: 85%

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Meyer

Metzger

2003

Analytical and Bioanalytical Chemistry

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Electrospray ionization mass spectrometry (ESI-MS) coupled to a microreactor is an excellent tool for the investigation of reactions in solution. Here, we report the first results of our investigations into preparatively interesting electron-transfer-initiated chain reactions in solution which proceed via radical cations as reactive intermediates. The tris(p-bromophenyl)aminium hexachloroantimonate (1)-mediated [2+2] cycloaddition of trans-anethole (2) to give 1,2-bis(4-methoxyphenyl)-3,4-dimethylcyclobutane (3) was investigated. The reaction proceeds as a radical cation chain reaction via transient intermediates 2*+ and 3*+ that could be detected and characterized unambiguously directly in the reacting solution by ESI-MS/MS. The identity of the intermediates was confirmed by comparison with authentic MS/MS spectra of 2*+ and 3*+ obtained by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). In addition, substrate and product can be monitored easily in the reacting solution by APCI-MS.

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Section: Esi-ms Investigation Of the [2+2] Cycloaddition Of Trans-anementioning

confidence: 85%

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Meyer

Metzger

2003

Analytical and Bioanalytical Chemistry

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“…Depending on the method used, a long bond intermediate [26] (also rationalized in terms of resonance forms of a tetramethylene radical cation), [27] together with rhomboid, [28Ϫ30] rectangular, [31] and trapezium [32,33] structures have all been located. Each species has been claimed to account for the ESR hyperfine coupling constants observed experimentally, either for geometrical reasons [29,31] or thanks to available tunneling pathways.…”

Section: The Structure and [2؉2] Cycloreversion Of The Cyclobutane Ramentioning

confidence: 99%

Pericyclic Reactions of Radical Cations

Saettel¹,

Oxgaard²,

Wiest³

2001

Eur. J. Org. Chem.

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“…Ionized alkanes have easily elongated C-C bonds [34][35][36], so it is likely that as such a C-C bond is further stretched, simultaneous initiation of a Wagner-Meerwein-like 1,2-H shift facilitates bond breaking. The absence of an activation energy for conversion of primary alkyl cations to isomeric forms, for example, n-C 3Hi~i -C 3Hi [37], enables an H shift to anchimerically assist bond cleavage and to lower the barrier to C-C bond breaking in 1.…”

Section: Energy Dependence Of the Fragmentations Of 1 Andmentioning

confidence: 99%

A photoionization study of the ion-neutral complexes CH₃CH ⁺CH₃^·CH₂CH₃] and CH₃CH₂CH⁺CH₃^·CH₃ in the gas phase: Formation, H-transfer and C—C bond formation between partners, and channeling of energy into dissociation

Traeger

McAdoo

1996

J. Am. Soc. Mass Spectrom.

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Photoionization mass spectrometry was used to investigate the dynamics of ion-neutral complex-mediated dissociations of the n-pentane ion (1). Reinterpretation of previous data demonstrates that a fraction of ions 1 isomerizes to the 2-methylbutane ion (2) through the complex [CH 3CH+CH3'CH 2CH 3] (3), but not through [CH 3CH+CH 2CH 3'CH 3] (4). The appearance energy for C3H~formation from 1 is 66 k] mol-I below that expected for the formation of I1-C3H~and just above that expected for formation of i-C 3H 7 • This demonstrates that the H shift that isomerizes C3H~is synchronized with bond cleavage at the threshold for dissociation to that product. It is suggested that ions that contain n-alkyl chains generally dissociate directly to more stable rearranged carbenium ions. Ethane elimination from 3 is estimated to be about seven times more frequent than is C -C bond formation between the partners in that complex to form 2, which demonstrates a substantial preference in 3 for H abstraction over C-C bond formation. In 1 -+ CH 3CH+CH 2CH 3 +' CH 3 by direct cleavage of the C1-C2 bond, the fragments part rapidly enough to prevent any reaction between them. However, 1 -+ 2 -+ 4 -+ C 4Hs '+ CH 4 occurs in this same energy range. Thus some of the potential energy made available by the isomerization of I1-C 4H 9 in 1 is specifically channeled into the coordinate for dissociation. In contrast, analogous formation of 3 by 1 --+ 3 is predominantly followed by reaction between the electrostatically bound partners. {J Am Soc Mass Spectrom 1996, 7, 73-81) I on-neutral complexes (ionic and neutral fragments held together primarily by noncovalent attractions) are often intermediates in low energy dissociations of ions in the gas phase [1][2][3][4][5]. As the energy in an ion is increased toward the threshold for simple dissociation, partial dissociation to noncovalently bound fragments that can react with each other begins to occur [6][7][8]. Determination of how such reactions depend on energy provides unique information on interactions between ions and neutrals at energies from just below to just above the threshold for separation of the partners-an energy regime that is not readily accessed by other means. Little detailed experimental information exists on such interactions.To understand better the dynamics of complexmediated reactions, we undertook a study of the en- ergy dependence of pertinent dissociations of the isomers ionized n-pentane (1) and 2-methylbutane (2). Scheme I, which is similar to one presented by Wendelboe et al. [9], summarizes the reactions we will characterize for this purpose. It includes three possible mechanisms for alkyl isomerization upon dissociation of 1: dissociation to complexes (species enclosed in brackets in Scheme I and throughout this contribution) followed by isomerization of the alkyl ion partner (reactions c and d) [9], concerted C-C bond cleavage and isomerization (reaction a) [10], and complex formation by isomerization-bond scission (reactions b and e). Simple bond cleavage to form...

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Elongated (one-electron) carbon-carbon bond in .sigma. and n organic cation radicals

Cited by 45 publications

References 0 publications

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Pericyclic Reactions of Radical Cations

A photoionization study of the ion-neutral complexes CH₃CH ⁺CH₃^·CH₂CH₃] and CH₃CH₂CH⁺CH₃^·CH₃ in the gas phase: Formation, H-transfer and C—C bond formation between partners, and channeling of energy into dissociation

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Elongated (one-electron) carbon-carbon bond in .sigma. and n organic cation radicals

Cited by 45 publications

References 0 publications

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations

Pericyclic Reactions of Radical Cations

A photoionization study of the ion-neutral complexes CH3CH +CH3·CH2CH3] and CH3CH2CH+CH3·CH3 in the gas phase: Formation, H-transfer and C—C bond formation between partners, and channeling of energy into dissociation

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A photoionization study of the ion-neutral complexes CH₃CH ⁺CH₃^·CH₂CH₃] and CH₃CH₂CH⁺CH₃^·CH₃ in the gas phase: Formation, H-transfer and C—C bond formation between partners, and channeling of energy into dissociation