Propyl ions and protonated cyclopropane as intermediates in the reaction of methyl cations with ethylene

Abernathy, R. N.; Lampe, F. W.

doi:10.1016/0020-7381(81)85013-9

Cited by 8 publications

(11 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The iC 3 H 7 cation is recognized as the most stable isomer. [1] As the conjugate acid of propene, its heat of formation is of fundamental importance in gas-phase thermochemistry.…”

Section: Introductionmentioning

confidence: 99%

“…[2] The ion iC 3 H 7 is also the simplest all-carbon and hydrogen carbenium ion to be prepared as a stable species in superacid media, [3] in which it was found to undergo scrambling of both hydrogen and carbon atoms. [4,5] The key intermediates and/or transition structures for these processes were suggested to be nC 3 H 7 and cC 3 H 7 . [4] The cC 3 H 7 ion itself has been identified as a discrete species in the gas-phase in which propene and cyclopropane are characterized by nearly the same proton affinity (PA).…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, whereas the lifetime of gaseous cC 3 H 7 ions is estimated to exceed 10 À7 s, an isomerization to iC 3 H 7 has been suggested to account for the identical collisional activation spectra of the ions obtained by the protonation of cyclopropane and propene after a time lapse of about 10 À5 s. [6c] cC 3 H 7 ions have been proposed to play a role in various ionic processes in the gas phase. For example, it has been suggested as the intermediate in the CH 3 reaction with ethylene [7] and it has been conceived as the possible product ion of the hydrogen atom loss from ionized propane. [8] The metastable dissociation of propane molecules from cluster ions of C 3 H 7 with neat propane or Ar/ propane has also been ascribed to the isomerization of a cC 3 H 7 core to give iC 3 H 7 proceeding by way of a transient nC 3 H 7 .…”

Section: Introductionmentioning

confidence: 99%

“…For example, it has been suggested as the intermediate in the CH 3 reaction with ethylene [7] and it has been conceived as the possible product ion of the hydrogen atom loss from ionized propane. [8] The metastable dissociation of propane molecules from cluster ions of C 3 H 7 with neat propane or Ar/ propane has also been ascribed to the isomerization of a cC 3 H 7 core to give iC 3 H 7 proceeding by way of a transient nC 3 H 7 . [9] The difference between the heats of formation of nC 3 H 7 and iC 3 H 7 has been determined as 87 kJ mol À1 according to photoelectron spectroscopy data, though all attempts to trap nC 3 H 7 have shown that it rearranges in less than 10 À10 s. [6b, 10] The present paper describes an experimental study on the protonation of cyclopropane by gaseous Brùnsted acids of different acid strength, aimed to assess the significant factors affecting the formation of cC 3 H 7 and its isomerization into iC 3 H 7 .…”

Section: Introductionmentioning

confidence: 99%

“…The experiments have been performed at pressures close to one atmosphere, under conditions ensuring efficient collisional thermalization of excited intermediates, and by using the radiolytic method for the generation of ions. [11] The ionic species of interest, cC 3 H 7 and iC 3 H 7 , were trapped by reaction with benzene. The ensuing products of electrophilic aromatic substitution, nC 3 H 7 ÀC 6 H 5 and iC 3 H 7 ÀC 6 H 5 , provide a dependable probe of the relative amounts of cC 3 H 7 and iC 3 H 7 , respectively, that are present in the ionic medium.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

The Protonation of Gaseous Cyclopropane

et al. 2001

View full text Add to dashboard Cite

The protonation of cyclopropane by gaseous Brønsted acids of varying strength in radiolytic experiments at atmospheric pressure leads to two distinct C3H7- isomers that have been sampled by their reaction with benzene. The neutral end products, nC3H7-C6H5 and iC3H7-C6H5, arise from the electrophilic aromatic substitution reaction with the cC3H7+ and iC3H7+ ions, respectively. Their relative abundance was studied as a function of pressure, temperature, and the presence of additives in the gaseous systems; the results indicate a large extent of isomerization to the thermodynamically favored iC3H7+ from the protonation by strong acids. The presence of a kinetic barrier prevents any thermal isomerization from taking place in the time frame of 10(-8) s. In the peculiar case in which protonated benzene is the Brønsted acid, C3H7+ ions are formed in the presence of neutral benzene within the same ion - molecule complex. The ensuing reaction shows that cC3H7+ ions are formed exclusively and react in the 10(-10) s(-1) estimated lifetime of the complex. Still, such cC3H7+ ions undergo complete randomization of their hydrogen atoms; this points to a low kinetic barrier for the process. Agreement is found between the reported experimental results and updated computations of the relevant species in the C3H7+ potential energy surface.

show abstract

“…The iC 3 H 7 cation is recognized as the most stable isomer. [1] As the conjugate acid of propene, its heat of formation is of fundamental importance in gas-phase thermochemistry.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Protonation of Gaseous Cyclopropane

et al. 2001

View full text Add to dashboard Cite

show abstract

Mass Spectra of Double‐Bonded Groups

Gäumann

2009

Patai's Chemistry of Functional Groups

View full text Add to dashboard Cite

An Introduction, to Warm Up The Localization of the C  C Double Bond: an Analytical Problem Ethylene: An Old Faithful The Pentene Story Heptene: The Other Story Alkenes: To Fill Some Gaps Acetone, Seemingly Simple Other Ketones: The More it Changes, the More It Is the Same Diels–Alder and Retro‐Diels–Alder Reactions Acknowledgments

show abstract

Cationated cyclopropanes as reaction intermediates in mass spectra: an earlier incarnation of ion‐neutral complexes

Meyerson¹

1989

Org. Mass Spectrom.

View full text Add to dashboard Cite

The appearance a decade ago of the concept of ion-neutral complexes as intermediates in unimolecular decompositions constituted a major advance in mechanistic interpretation of mass spectra. The concept, however, was not new; it goes back to the introduction of the cationated cyclopropane in the mid-1950s. Its development did not occur via a smooth progression; rather, its history bridges a sharp discontinuity. The early workers, in a curious historical quirk, failed to generalize on the idea beyond complexes in which the neutral component is cyclopropane or a closely related species. Hence it took an independent rediscovery of the concept to usher in the rapid growth and wide application that characterize its present stage of development.The first mass spectra of organic compounds were reported in the late 1920s to mid-1930~.'.~ These reports represented the beginning of a research task that has engaged the efforts of a great many workers over the half-century that has elapsed since then: the construction of a systematic chemistry of gaseous organic ions, concentrated chiefly on unimolecular proc e~s e s .~ As late as 1954, progress was still limited enough and prospects sufficiently problematical to prompt a prominent speaker4 at a national conference to propose that much of this chemistry takes place via 'sudden death', in which electron impact introduces so much energy into a molecule that the atoms of which it is composed lose all memory of their original configuration, fall into a clump, and then try to reorganize themselves as well as they can into stable products. This proposal drove home with vivid clarity to the listeners some notion of how long and tortuous we might expect to find the path on which we had started to travel.A major conceptual advance in the development of this chemistry occurred a decade ago with the appearance of several important papers postulating ionneutral complexes as intermediates in unimolecular decompositions ;5 they were by then already well established in bimolecular reactions. The idea here is that the charged and neutral products of ion dissociation may remain in close proximity for a long enough period of time after formation to allow chemical interaction before they separate. The persistence of such a complex is rationalized in terms of attraction between an ion and dipole or an ion and induced dipole. Intervention of independent rotation of the components of the complex allows interaction between molecular groupings that would not have been sterically accessible to each other in the original molecule.t Presented in part before the Eleventh Conference of the Australian and New Zealand Society for Mass Spectrometry, Inc., Brisbane, 15-19 May 1988. Such complexes proved successful in resolving enough puzzling observations that they quickly gained wide acceptance. They are now firmly established as a valid and invaluable concept in deducing the chemistry underlying mass spectra: enough so that the 1986 Annual Conference on Mass Spectrometry and Allied Topics, under the au...

show abstract

Propyl ions and protonated cyclopropane as intermediates in the reaction of methyl cations with ethylene

Cited by 8 publications

References 17 publications

The Protonation of Gaseous Cyclopropane

The Protonation of Gaseous Cyclopropane

Mass Spectra of Double‐Bonded Groups

Cationated cyclopropanes as reaction intermediates in mass spectra: an earlier incarnation of ion‐neutral complexes

Contact Info

Product

Resources

About