I. Howe, D. H. Williams and R. D. Bowen. Mass spectrometry, principles and applications, 2nd edition. McGraw-Hill Inc., New York, 1981

Bowen, David V.

doi:10.1002/bms.1200091110

Cited by 22 publications

(31 citation statements)

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“…In agreement with the EI study of ions 1 to 7 (12), only two metastable fragmentation reactions of C5H,10+ ions were observed, corresponding to elimination of H20 (reaction [2]) and elimination of C3H6 (reaction [5]). Table 5 records the intensity ratio (C5Hy+ + C3H5+)/C2H50+ observed in the CI mass spectra and in the metastable ion mass spectra following both C1 and EI ionization; this ratio represents the relative importance of fragmentation reactions [2] and [5] for the ions studied.…”

Section: Unimoleculdr Ion Chemistrysupporting

confidence: 87%

“…Ions 1, 2, 6, and 8 show reaction [5] as the major fragmentation channel while ions 3, 4, 7, 9, 10, and 11 show CsHy+ as the dominant fragment ion. In the H2 CI mass spectrum, ion 5 shows C3H7+ as the base peak (reaction [6]) although reaction [2] becomes the major reaction channel as the protonation exothermicity decreases from H3+ to CHO'.…”

Section: Unimoleculdr Ion Chemistrymentioning

confidence: 99%

“…Table 5 records the intensity ratio (C5Hy+ + C3H5+)/C2H50+ observed in the CI mass spectra and in the metastable ion mass spectra following both C1 and EI ionization; this ratio represents the relative importance of fragmentation reactions [2] and [5] for the ions studied. significantly less than that of CH,CHOH+ + C3H6 (-602 kJ mol-') yet both fragmentation reactions are observed as metastable ions (for the thermochemical data, see the Appendix).…”

Section: Unimoleculdr Ion Chemistrymentioning

confidence: 99%

“…Indeed, the study of these systems played a large role in the development of the potential energy profile approach (4)(5)(6) to the interpretation of the low energy unimolecular chemistry of isolated gaseous organic ions. The C,,H2,,, '0' ions also can be prepared by proton transfer chemical ionization of carbonyl compounds and cyclic ethers and, recently, the chemistry of the C3H70t ions (7,8) and C4H90t ions (9) formed by proton transfer chemical ionization have been studied in detail and interpreted in terms of the potential energy profiles established from the earlier EI studies.…”

Section: Introductionmentioning

confidence: 99%

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Structure and fragmentation of C₅H₁₁O⁺ ions formed by chemical ionization

Headley¹,

Harrison²

1985

Can. J. Chem.

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. J . Chem. 63, 609 (1985). The proton transfer chemical ionization mass spectra of eleven C5HI,,0 isomers have been obtained using H3+, NZH+, HCO', and D3' as reagent ions. The chemical ionization mass spectra in combination with isotopic labelling and metastable ion studies have made it possible to elucidate the major fragmentation reaction channels of the C5H,,0' ions formed and their dependence on precursor structure. From collision induced dissociation studies nine stable distinct C5H Introduction The C,,H2,, i. ,O' ions are abundant fragment ions in the electron impact mass spectra of aliphatic alcohols and ethers (1) and, because of their widespread occurrence, have received extensive study with respect to their thermochemistry, structures, and unimolecular fragmentation reactions. The thermochemistry of the lower members of the series (up to C,) is well established as a result of the elegant work of Lossing (2). The structures and low energy (metastable) unimolecular fragmentation reactions of the C2H50t, C3H70i, and C4H,0t ions formed by electron impact have been studied exhaustiv~ly by many groups and are now well understood (for a review and summary of these studies see ref.3). Indeed, the study of these systems played a large role in the development of the potential energy profile approach (4-6) to the interpretation of the low energy unimolecular chemistry of isolated gaseous organic ions. The C,,H2,,, '0' ions also can be prepared by proton transfer chemical ionization of carbonyl compounds and cyclic ethers and, recently, the chemistry of the C3H70t ions (7,8) and C4H90t ions (9) formed by proton transfer chemical ionization have been studied in detail and interpreted in terms of the potential energy profiles established from the earlier EI studies. In this chemical ionization approach a number of structures, such as protonated cyclic ethers inaccessible by electron impact methods, become available for study.In contrast to the extensive studies of the lower members of the series, the higher members of the C,,H,,,, '0' series have received much less attention. McLafferty and Sakai (10) have reported the collision-induced dissociation (CID) mass spectra of a few C 5 H l 1 0 t ions, while Zahorszky (1 1) has surveyed briefly the unimolecular ion chemistry of higher members of the series. The most extensive study has been that of Audier et al. (12) of the C5HIIOt ions of nominal structures 1 to 7 (Scheme I ) prepared by electron impact methods. They studied not only the unimolecular metastable ion chemistry but also the CID mass spectra, and were able to show that all the ions

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Section: Unimoleculdr Ion Chemistrysupporting

confidence: 87%

Section: Unimoleculdr Ion Chemistrymentioning

confidence: 99%

Section: Unimoleculdr Ion Chemistrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and fragmentation of C₅H₁₁O⁺ ions formed by chemical ionization

Headley¹,

Harrison²

1985

Can. J. Chem.

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“…In particular, a recent high level ab initio study [23] of n-butane and 2-methylpropane ions, adjacent homologs to the ions studied here, demonstrates quite clearly that elimination of methane by those ions is complex-mediated, so this work will proceed from the assumption that alkane eliminations from 1 and 2 are complex-mediated also. Substantial energy is sometimes made available by isomerization of ions to more stable structures [24][25][26]. This has been proposed to influence the dissociations of 1 [9], which leads us to investigate here whether energy made available by isomerization that accompanies bond breaking in 1 to form complexes selectively affects subsequent reactions.…”

mentioning

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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