Loss of CO from the molecular ions of 2,2‐dimethyl‐3,5‐hexandione

Grützmacher, Hans‐Friedrich; Masur, Monika

doi:10.1002/oms.1210230313

Cited by 11 publications

(4 citation statements)

References 8 publications

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“…102-103 "C (lit.29 m.p. 103-104 "C) was prepared from 7 and methyllithium as described in the literature.,' MS (70 eV), m/z 174 (11, M"), 159, (100, [M -CH,]+), 146 (0.25, not corrected), 145 (5), 131 (32), 129 (2), 128 (6), 127 (4), 105 (15), 103 (18), 102 (7), 91 (4), 77 (28). 'H NMR (300 MHz, CDCl,), 6 (ppm) 1.65 (s, 3 H; CH,), 2.28 (br, s, 1 H; OH), 6.31 and 7.03 (AB spin system, 35 = 10.2 Hz, 2 H ; 2-H and 3-H, respectively), 7.44, 7.64, 7.79, and 8.07 (ABCD spin system, 35 z 7.7 Hz, 45 % 1.0 Hz, 4 H; H"').…”

Section: Resultsmentioning

confidence: 99%

Mass spectrometric fragmentation of isomeric 2‐alkyl‐substituted 1,3‐indandiones and 3‐alkylidenephthalides: a seven‐step consecutive isomerization of regular and distonic molecular radical cations

Kuck

1994

Org. Mass Spectrom.

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The electron impact-induced fragmentation of 2,2-dimethyl-and 2-ethyI-l,findandione, 1 and 2, and their isomers, 3-isopropylidene-and 3-propylidenephthalide, 3 and 4, respectively, was studied in detail by mass-analysed ion kinetic energy (MIKE) and collision-induced dissociation (CID-MIKE) spectrometry, including 'H and I3C-labelled analogues of 1 and 2. In all regimes of internal energy, the molecular ions 1" -4" interconvert by up to seven consecutive, reversible isomerization steps prior to the main fragmentation processes, viz. loss of CH,' and C,H,. 1,3-Indandione and 3-methylenephthalide ions with identical alkylidene moieties (i.e. 1 +' e 3" and 2+' e 4+') equilibrate rapidly and completely prior to fragmentation, whereas these pairs of isomers interconvert only slowly via a five-step rearrangement of the indandione ions 1+'=2+'. Distinct from the behaviour of simpler ionized carbonyl species, a 1,2-C shift of a (formally) neutral carbonyl group is found to occur along with that of a protonated one. Also distinct from simpler cases, methyl loss does not take place from the ionized enol intermediates formed within the interconversion 1 +' + 2" of the diketone ions but rather from the n-propylidenephthalide ions 4+'. This follows from CID-MIKE spectrometry of the IM -CH,] + ions of 1-4 and two reference C,oH70,+ (m/z 159) ions of authentic structures (protonated 2-methylene-l,3-indaodione and protonated 1,4-naphthoquinone). The characteristic CID fragmentation of the C, oH70, + ions is rationalized. Finally, the multistep isomerization of ionized 1,J-indandiones apparently also extends to higher homologues leg. 5" from 2-etbyl-2-methyl-1,3-indandione (5) and 6" from 2,2-diethyl-1,3-indandione (6)] : the ionized phthaloyl group of 1,findandione radical cations l+', 2+', 5+' and 6+', originally attached with its two acyl functionalities to the same carbon of the aliphatic chain, performs, in fact, a 'multi-step migration'.

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Section: Resultsmentioning

confidence: 99%

Mass spectrometric fragmentation of isomeric 2‐alkyl‐substituted 1,3‐indandiones and 3‐alkylidenephthalides: a seven‐step consecutive isomerization of regular and distonic molecular radical cations

Kuck

1994

Org. Mass Spectrom.

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“…Grutzmacher and Masur 4) have reasonably explained this dissociation by the idea of the ion-neutral complex. 6), 7) However, this type of dissociation is scarcely observed in the mass spectra of the compounds, RC 6 H 4 COX, 8) except for the case of X῍ F. 9) This is due to the extreme stability of substituted benzoyl ions, RC 6 H 4 CO ῌ .…”

Section: )῎5)mentioning

confidence: 97%

Methyl Migration in the Metastably Decomposing Acetylphenyl Ions, CH3COC6H4+ (m/z 119), Followed by the Loss of CO

Tajima

Minegishi

Nakajima

et al. 2005

J. Mass Spectrom. Soc. Jpn.

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The metastable ion dissociations of o-, m-, and p-acetylphenyl ions, CH3COC6H4ῌ (m/z 119), generated upon electron ionization from o-, m-, and p-diacetylbenzenes (CH3COC6H4COCH3, Mw : 162, 1῎3), have been investigated by use of mass-analyzed ion kinetic energy (MIKE) spectrometry in conjunction with thermochemistry. All these m/z 119 ions, which are generated by the consecutive losses of CH3 and CO from 1 ῌῌ ῎3 ῌῌ , dissociate to only the ion at m/z 91 by the loss of CO. These suggest that in the CH3COC6H4 ῌ ions, the CH3 migration from the acetyl group to the benzene ring occurs prior to the loss of CO. The amounts of the kinetic energy release (KER) accompanying with the dissociation of the m/z 119 ions from compounds 1῎3 to m/z 91 ion were larger than those of the corresponding, respective methylbenzoyl ions. In the m-, and p-CH3COC6H4 ῌ ions, the charge migrates from the incipient charge site to the ortho position via the so-called hydrogen "ring-walk." Then CH3 migrates from the acetyl group to the charge site at the ortho position in the benzene ring prior to the loss of CO. A part of the m/z 91 ions from o-, m-, and p-acetylphenyl ions may be generated via the migration of CH3 to the incipient charge site, followed by the loss of CO.

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“…9) It has been proposed that the CO loss occurs via the ion-neutral complex from the molecular ions of acetylacetone, which is one of the b-diketones, to give the molecular ions of 2-butanone. 20) According to the Grutzmacher and Masur, 20) we propose an alternative mechanism of the generation of the m/z 88 ions by the loss of C 3 H 4 O 2 (CO ῌ CH 3 CHO) from 1 ῌῌ . Scheme 2 shows the fragmentation mechanism of 1-d 6 ῌῌ instead of 1 ῌῌ .…”

Section: )῎19)mentioning

confidence: 99%

Unimolecular Reactions of Diethyl Malonate Cation in Gas-phase

Tajima

Ishiguro

Mamada

et al. 2004

J. Mass Spectrom. Soc. Jpn.

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Unimolecular reactions of diethyl malonate cation (CH3CH2OC(῎O)CH2C(῎O)OCH2CH3ῌῌ ; 1 ῌῌ , Mw : 160) induced by electron ionization, have been investigated by use of mass-analyzed ion kinetic energy (MIKE) spectrometry and D-labeling in conjunction with thermochemistry. In the metastable time window, the molecular ions ῌ ) ions decompose into the ions at m/z 115, 106, and 105 by the losses of H2O, C2H3, and C2H4, respectively. A large part of the first fragment ions would be in the keto form and it decomposes into the m/z 71 and 43 ions by the losses of CO2 and C3H4O2 (or C2O3), and a small part would be in the enol form and decomposes into the m/z 87 ions by the loss of C2H4, not CO. The m/z 43 ions are isobaric, C2H3Oῌ and C3H7 ῌ .

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Loss of CO from the molecular ions of 2,2‐dimethyl‐3,5‐hexandione

Cited by 11 publications

References 8 publications

Mass spectrometric fragmentation of isomeric 2‐alkyl‐substituted 1,3‐indandiones and 3‐alkylidenephthalides: a seven‐step consecutive isomerization of regular and distonic molecular radical cations

Mass spectrometric fragmentation of isomeric 2‐alkyl‐substituted 1,3‐indandiones and 3‐alkylidenephthalides: a seven‐step consecutive isomerization of regular and distonic molecular radical cations

Methyl Migration in the Metastably Decomposing Acetylphenyl Ions, CH3COC6H4+ (m/z 119), Followed by the Loss of CO

Unimolecular Reactions of Diethyl Malonate Cation in Gas-phase

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