Dissociation of positively charged aliphatic epoxides. II. [C5H10O]+˙ epoxides and α,β unsaturated ethers

Bouchoux, Guy; Djazi, Fayçal; Hoppilliard, Y.; Jaudon, P.; Nouts, Nathalie

doi:10.1002/oms.1210230107

Cited by 10 publications

(3 citation statements)

References 33 publications

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“…Typically, the isomerization occurs by bond cleavage of a cyclic molecular ion or by an internal hydrogen abstraction. Thus the distonic ion "CH2-O-CH ~-may be formed by cleavage of the C-C bond in oxirane radical cations [11], and an intermolecular hydrogen abstraction is usually the initial step for the loss of H20 and related elimination processes (see Schemes 2 and 4). Clearly the mechanism of the elimination depends critically on the properties of the initially formed distonic ion as a reactive intermediate.…”

Section: Intermediate Distonic Ionsmentioning

confidence: 99%

Unimolecular reaction mechanisms: the role of reactive intermediates

Grützmacher

1992

International Journal of Mass Spectrometry and Ion Processes

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Many ummolecular mass spectrometric fragrnentaUons do not occur directly from the mmzed but otherwise intact molecules, but revolve lsomenzat~on to reactwe intermediates as the critical step of the fragmentation mechamsm During the last few years, distomc ions and ion/neutral complexes have been identified as important intermediates of mass spectrometric fragmentations Examples are taken from the recent hterature and from our own unpubhshed results to dlummate the role of these intermediates, in particular for rearrangement reactions by remote group mteractmn INTRODUCTION

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Section: Intermediate Distonic Ionsmentioning

confidence: 99%

Unimolecular reaction mechanisms: the role of reactive intermediates

Grützmacher

1992

International Journal of Mass Spectrometry and Ion Processes

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“…•+ species may be explained by postulating the intermediacy of INCs. 18,19 In contrast to most categories of C n H 2n O…”

Section: Introductionmentioning

confidence: 97%

“…Various reviews 1-5 summarise the intriguing chemistry that has been reported for a wide range of ionised C n H 2n O species, including aldehydes and ketones, [6][7][8][9][10][11][12] alkenols and cycloalkanols [13][14][15] and cyclic ethers. [16][17][18][19] Many C n H 2n O •+ species undergo hydrogen transfer and even skeletal isomerisation before dissociating. Distonic ions 20,21 and ion-neutral complexes (INCs) [22][23][24][25][26][27][28] frequently are of crucial importance in the rearrangements which precede fragmentation of these ions.…”

Section: Introductionmentioning

confidence: 99%

Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C₅H₉OCH₃^•+

Bowen

Trikoupis

Terlouw

2001

Eur J Mass Spectrom (Chichester)

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The dissociation chemistry of the low-energy C 5 H 9 OCH 3 •+ ions generated from the 13 isomeric pentenyl methyl ethers derived from stable alkenols has been studied. This was done by examining their metastable ion characteristics, in conjunction with 2 H and 13 Clabelling as well as collision-induced dissociation and neutralisation-reionisation experiments. The influence of the position and substitution pattern of the double bond on the chemistry of these C 6 H 12 O •+ species is considered. The closely similar reactions of C 2 H 5 CH=CHCH 2 OCH 3 •+ , 3 •+ , CH 2 =CH-CH(C 2 H 5)OCH 3 •+ , 4 •+ , and CH 2 =C(C 2 H 5)CH 2 OCH 3 •+ , 13 •+ , point to a common chemistry, which is rationalised in terms of facile 1,2-H and 1,2-C 2 H 5 shifts via distonic ions. Each of the other isomers displays a distinct, though often related, chemistry. The eight allylic ionised ethers easily lose CH 3 • to produce C 5 H 9 O + oxonium ions, whose structure was established by CID experiments; ions 3 •+ / 4 •+ / 13 •+ also readily expel C 2 H 5 • to give C 4 H 7 O + ions of structure CH 2 =CH-C + (H)OCH 3. Elimination of CH 3 OH is also significant for 3 •+ / 4 •+ / 13 •+ and for (CH 3) 2 C=CHCH 2 OCH 3 •+ , 8 •+ , and CH 3 CH=C(CH 3)CH 2 OCH 3 •+ , 11 •+. Besides expelling CH 3 • and/or C 2 H 5 • and CH 3 OH, the three homoallylic isomers undergo dissociations which are (almost) absent for their allylic counterparts: thus, both CH 3 CH=CH(CH 2) 2 OCH 3 •+ , 2 •+ , and CH 2 =CH-CH(CH 3)CH 2 OCH 3 •+ , 10 •+ , lose H • and H 2 O, whereas CH 2 =C(CH 3)CH 2 CH 2 OCH 3 •+ , 7 •+ , is unique in predominantly losing CH 2 O. For the losses of CH 2 O and H 2 O mechanisms are proposed in which ion-neutral complexes of the type [C 5 H 10 •+ / CH 2 O] and [C 6 H 10 •+ / H 2 O] are key intermediates. The behaviour of the non-(homo)allylic isomer, CH 2 =CH(CH 2) 3 OCH 3 •+ , 1 •+ , is similar to that of 2 •+ but the reactions occur in different proportions. A mechanism for the facile loss of an alkyl radical from 1 + is proposed in which 1,4-H shifts and distonic ions as well as communication with ionised cyclopentyl methyl ether, 14 •+ , play an important role.

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Rearrangement reactions of the molecular ions of some substituted aliphatic oxiranes

Grützmacher

Pankoke

1989

Org. Mass Spectrom.

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The fragmentation reactions of glycidic methyl ester (1) and of its derivatives (26) substituted by one, two and three methyl groups, respectively, at the oxirane ring, of the corresponding glycidols (7-12), and of the glycidyl ethers (13-16) in the 70 eV mass spectra have been studied using isotopic labelling and mass-analysed ion kinetic energy spectrometry. It is shown that the typical reaction of these aliphatic oxirane radical cations carrying a nucleophilic methoxy group and hydroxy group, respectively, at the side chain corresponds under high-energy conditions to a rearrangement by a methoxy group or a hydroxy group migration to the p-carbon atom of the oxirane moiety. This rearrangement is very likely mediated by the isomerization of the molecular ions into distonic ions via C-C bond cleavage within the oxirane ring.

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Dissociation of positively charged aliphatic epoxides. II. [C₅H₁₀O]⁺˙ epoxides and α,β unsaturated ethers

Cited by 10 publications

References 33 publications

Unimolecular reaction mechanisms: the role of reactive intermediates

Unimolecular reaction mechanisms: the role of reactive intermediates

Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C₅H₉OCH₃^•+

Rearrangement reactions of the molecular ions of some substituted aliphatic oxiranes

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Dissociation of positively charged aliphatic epoxides. II. [C5H10O]+˙ epoxides and α,β unsaturated ethers

Cited by 10 publications

References 33 publications

Unimolecular reaction mechanisms: the role of reactive intermediates

Unimolecular reaction mechanisms: the role of reactive intermediates

Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C5H9OCH3•+

Rearrangement reactions of the molecular ions of some substituted aliphatic oxiranes

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Dissociation of positively charged aliphatic epoxides. II. [C₅H₁₀O]⁺˙ epoxides and α,β unsaturated ethers

Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C₅H₉OCH₃^•+