Effect of the ion stability on the fate of intermediate ion/neutral complexes

Grützmacher, Hans‐Friedrich; Thielking, Gerhard; Wittneben, Doris; Eikenberg, Dirk

doi:10.1016/0168-1176(90)80006-o

Cited by 13 publications

(6 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore the mechanism in Scheme 14 implies that the branching between ester elimination and acyl cation formation should depend on the (relative) stability of the acyl cation. This is supported by the experimental results [38]. Table 1 shows the MIKE spectra of a series of 4-methoxymethyl-substituted phenones, originally protonated at the carbonyl group.…”

Section: Intermediate Ion/neutral Complexessupporting

confidence: 67%

“…The explanation for this effect is a barrier to the "ring-walk" migration of the proton around the naphthalene system imposed by the ring junction. This has been supported by MNDO calculations of the heat of formation of the relevant protomers [38]. Analogously, it is difficult for a proton to cross by successive 1,2-shifts from one benzene ring to the other in the diphenyl and terphenyl systems, as depicted in Scheme 15, because of the energetically unfavourable ipso protomers.…”

Section: Intermediate Ion/neutral Complexesmentioning

confidence: 72%

“…Nevertheless, the relative abundance of the elimination of methyl acetate, mediated by a complex composed of the acetyl cation and the arylmethyl methyl ether, increases distinctly at the expense of the methanol elimination. Again, the study of deuterated derivatives shows clearly [38] that the ester molecule originates from the acetyl and methoxy group without any H/D exchange, excluding other "conventional" fragmentation mechanisms.…”

Section: Intermediate Ion/neutral Complexesmentioning

confidence: 99%

See 2 more Smart Citations

Unimolecular reaction mechanisms: the role of reactive intermediates

Grützmacher

1992

International Journal of Mass Spectrometry and Ion Processes

Self Cite

View full text Add to dashboard Cite

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

show abstract

Section: Intermediate Ion/neutral Complexessupporting

confidence: 67%

Section: Intermediate Ion/neutral Complexesmentioning

confidence: 72%

Section: Intermediate Ion/neutral Complexesmentioning

confidence: 99%

See 1 more Smart Citation

Unimolecular reaction mechanisms: the role of reactive intermediates

Grützmacher

1992

International Journal of Mass Spectrometry and Ion Processes

Self Cite

View full text Add to dashboard Cite

show abstract

“…And the mobile proton model13–18 which describes the mobility of the proton across the protonated molecule is proposed and applied not only to the flexible peptides and proteins but also to the rigid molecules. In fact, the mobile characteristic of proton was first observed and unambiguously characterized by Grutzmacher and co‐workers 19–24. Take naphthalene with a carbonyl group on one end and a methoxymethyl on the other for example,21 they observed that the ionizing proton which is definitely attached to the carbonyl oxygen migrates across the ring to the oxygen atom of the methoxy group, leading to the elimination of methanol.…”

Section: Introductionmentioning

confidence: 95%

An experimental and computational investigation on the fragmentation behavior of enaminones in electrospray ionization mass spectrometry

Guo

Wan

et al. 2010

J. Mass Spectrom.

View full text Add to dashboard Cite

The dissociation pathways of protonated enaminones with different substituents were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in positive ion mode. In mass spectrometry of the enaminones, ArCOCHCHN(CH(3) )(2) , the proton transfers from the thermodynamically favored site at the carbonyl oxygen to the dissociative protonation site at ipso-position of the phenyl ring or the double bond carbon atom adjacent to the carbonyl leading to the loss of a benzene or elimination of C(4) H(9) N, respectively. And the hydrogendeuterium (H/D) exchange between the added proton and the proton of the phenyl ring via a 1,4-H shift followed by hydrogen ring-walk was witnessed by the D-labeling experiments. The elemental compositions of all the ions were confirmed by ultrahigh resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FTICR-MS/MS). The enaminones studied here were para-monosubstituted on the phenyl ring and the electron-donating groups were in favor of losing the benzene, whereas the electron-attracting groups strongly favored the competing proton transfer reaction leading to the loss of C(4) H(9) N to form a benzoyl cation, Ar-CO(+) . The abundance ratios of the two competitive product ions were relatively well-correlated with the σ(p) (+) substituent constants. The mechanisms of these reactions were further investigated by density functional theory (DFT) calculations.

show abstract

“…In fact, it has been shown [7] by varying the acyl substituent RCO, that the fragmentation by the internal ion-neutral reaction occurs only as long as the direct dissociation is not favored by yielding an especially stable acyl cation RCO+. Another interesting modification of this model system is a change of the benzene nucleus by a larger aromatic group.…”

mentioning

confidence: 99%

Remote fragmentations of protonated aromatic carbonyl compounds via internal reactions in intermediary ion-neutral complexes

Thielking

Filges

Grützmacher

1992

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

Protonated aromatic aldehydes and methyl ketones la-lOa, carrying initially the proton at the carbonyl group, are prepared by electron impact-induced loss of a methyl radical from 1-arylethanols and 2-aryl-Bpropanols, respectively. The aryl moiety of the ions corresponds to a benzene group, a naphthalene group, a phenanthrene group, a biphenyl group, and a terphenyl group, respectively, each substituted by a CH30CH2 side-chain as remote from the acyl substituent as possible. The characteristic reactions of the metastable ions, studied by mass-analyzed ion kinetic energy spectrometry, are the elimination of methanol, the formation of CH,OCH$ ions, and the elimination of an ester RCOOCH, (R = H and CH,). The mechanisms of these fragmentations were studied by using D-labeled derivatives. Confrrming earlier results, it is shown that the ester elimination, at least from the protonated aryl methyl ketones, has to proceed by an intermediate [acyl cation/arylmethyl methyl etherl-complex. The relative abundances of the elimination of methanol and of the ester decrease and increase, respectively, with the size of the aromatic system. Clearly, the fragmentation via intermediate ion-neutral complexes is favored for the larger ions. Furthermore, the acyl cation of these complexes can move unrestricted over quite large molecular distances to react with the remote CH30CH,-side-chain, contrasting the restricted migration of a proton by 1,2-shifts ("ring walk") in these systems. (J Am Sot Mass Spectrom 1992, 3,[417][418][419][420][421][422][423][424][425][426]

show abstract

Effect of the ion stability on the fate of intermediate ion/neutral complexes

Abstract: Carbonyl protonated aromatic ketones a

Cited by 13 publications

References 14 publications

Unimolecular reaction mechanisms: the role of reactive intermediates

Unimolecular reaction mechanisms: the role of reactive intermediates

An experimental and computational investigation on the fragmentation behavior of enaminones in electrospray ionization mass spectrometry

Remote fragmentations of protonated aromatic carbonyl compounds via internal reactions in intermediary ion-neutral complexes

Contact Info

Product

Resources

About