Kinetic energy release and position of the transition state during the intramolecular substitution of ionized benzalacetones

Schaldach, Bernd; Grützmacher, Hans‐Friedrich

doi:10.1016/0020-7381(79)83028-4

Cited by 17 publications

(5 citation statements)

References 24 publications

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“…This corre sponds to a change in the transition state configura tions of the reacting molecular ions. This tendency is reflected by a parallel change in the abundance of [C6H7]+ ions; one expects [9] low values for the abun dance of the ions from all precursors since Xq >0.5. All C7H80 reactions (Table 2) follow that trend ex actly.…”

Section: Methodsmentioning

confidence: 99%

“…A correlation between the energy partitioning quotient q and Xq makes it possible to obtain exper imental information about the nature of the transition state produced in a mass-spectrometric fragmentation reaction, and thus provides more detailed data on these elementary reactions [9], The formation of [C6H 7]+ from benzyl alcohol, with a strongly endo thermic reaction (Xq=0.93), takes place with the transformation of nearly all available energy into trans lational energy measured as the maximum kinetic energy TB. This amount of energy is small (0.16 eV), as the available energy of the product-like transition state probably corresponds only to the freely fluctuat ing excess energy of the activated complex e*.…”

Section: Methodsmentioning

confidence: 99%

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Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors

Selim

Rabbih

Fahmey

1991

Zeitschrift Für Naturforschung A

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K in e tic E n e rg y R e le a s e a n d P o s itio n o f th e T ra n s itio n S t a te fo r (C 6H 7 The energetic requirement and mechanisms for CHO' loss from the molecular ions of isomeric C7HsO precursors have been reported. The heat of formation of [C6H7]+ (protonated benzene) was determined and e* evaluated. Measurement of the kinetic energy release TB gives the energy-partitioning quotients q= TB/£* which range from 0.38 to 0.99. The energy available and Tn are small for the strongly endothermic reaction of benzyl alcohol but increase sharply in the case of the weakly endothermic reaction of anisole. All reactions have "late" transition states, the position Xq of the transition state on the reaction coordinate varying from 0.64 to 0.93.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors

Selim

Rabbih

Fahmey

1991

Zeitschrift Für Naturforschung A

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“…Die Anwendung von Gleichung (3) liefert-die in Tab. 6 angegebenen X$Werte; Abb. 3 zeigt ein darnit konstruiertes Hammond-Diagramm der potentiellen Reaktionsenergie fiir 1 a -If.…”

Section: Diskussionunclassified

“…6. Position des Ubergangszustandes X; und Energieaufteilungsquotienl q. fur Substituentenabspaltung aus 2-Stilbazol-Ionen In der Gasphase wird die Anlagerung eines Protons an das freie Elektronenpaar des N-Atoms im Pyridin durch die wenig polare Styrylgruppe voraussichtlich wenig beeinfldt, so daR in der …”

Section: Diskussionunclassified

Freisetzung kinetischer Energie und Hammond‐Postulat bei der intramolekularen aromatischen Substitution in 2‐Stilbazol‐Ionen

1980

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In den Massenspektren der 2-Stilbazole l a -l g , sowie des 3-und CStilbazols (2 bzw. 3) werden durch Abspaltung eines H-Atoms oder des Substituenten mit hoher Intensitat C13HloN1 +-Ionen, m / z = 180, gebildet. Fiir metastabile Molekiil-Ionen von 1s-l g , 2 und 3 ist dies die einzige Zerfallsreaktion. Durch einen Vergleich der MI-und CA-Spektren der C13HIoN1 + -1onen ergibt sich, daR bei den 2-Stilbazolen l a -I g 4a-Azoniaphenanthren-lonen a durch eine intramolekulare Substitution in den Molekiil-Ionen entstehen. Die Abhangigkeit des Energiebedarfs und der Energie-Umsetzung bei dieser Reaktion von der Abgangsgruppe wird durch Messungen der Ionisations-und Auftrittsenergien sowie der bei der Reaktion freigesetzten kinetischen Energie untersucht. Danach verlauft die Reaktion iiber eine Zwischenstufe Z mit tetrakoordiniertem CAtom in der ortho-Position des Phenylringes, deren Bildung die Aktivierungsenergie der Gesamtreaktion bestimmt. Z entsteht als chemisch aktivierte Spezies und besitzt gegenuber einem Zerfall zu den Endprodukten iiberschiissige Energie. Die Aufteilung der uberschiissigen Energie auf innere Energie und Translationsenergie der Reaktionsprodukie wird von der Abgangsgruppe bestimmt. Diese Abhhgigkeit wird mit Hilfe eines quantitativen Hammond-Postulats durch die Position des ifbergangszustandes auf der Reaktionskoordinate beschrieben. Kinetic Energy Release and Hammond Postulate During Intramolecular Aromatic Substitution in 2-Stilbazole Ions 1)In the mass spectra of 2-stilbazoles l a -I g and 3-and 4-stilbazoles (2 resp. 3). C,,H,$I'+ ions, m/z = 180. are formed with high intensities by loss of a H-atom or of a substituent. This is the only fragmentation reaction available to metastable molecular ions of l a -Ig, 2. and 3. Comparison of MI and C A spectra of the C,,H,,N1 + ions shows, that 4a-azoniaphenanthrene ions a arise from the 2-stilbazoles l a -l g by an intramolecular substitution reaction of the molecular ions. The dependence of the energy requirements of this reaction has been studied by measurements of ionization and appearance energies and of the release of kinetic energy during the reaction. From this it follows that the reaction occurs via an intermediate Z with a tetracoordinated C-atom at the ortho-position of the phenyl group; the formation of Z determines the activation energy of the total reaction. Z is formed as a chemically activated species and contains excess energy with respect to fragmentation into the reaction products. The partitioning of the excess energy between internal and translational energy of the reaction products depends on the leaving group.This dependence is described with the aid of a quantitative Hammond postulate by the position of the transition state at the reaction coordinate.Massenspektrometrische Techniken zur Untersuchung metastabiler Ionen errnoglichen es, unimolekulare Reaktionen komplexer organischer Ionen in der Gasphase genauer als bisher zu untersuchen und interessante Hinweise auf den Ablauf chemischer Elementarreaktionen zu

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“… 5 Further evidence was obtained in a study that established that the 2-methylbenzopyrylium cation [ 3 , R = CH 3 ] is formed by loss of an ortho substituent from ionised benzalacetones [XC 6 H 4 CH=CHCOCH 3 ] +· . 6 The mechanism of these fragmentations, which may be interpreted as intramolecular aromatic substitutions, was later probed in considerable detail, 7 – 10 leading to a comprehensive review. 11 An alternative name for these processes, which emphasises their analytical significance, is ‘proximity effects’.…”

Section: Introductionmentioning

confidence: 99%

Proximity effects in the electron ionisation mass spectra of substituted cinnamamides

Michalik

Fenwick

Telford

et al. 2023

Eur J Mass Spectrom (Chichester)

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The electron ionisation mass spectra of an extensive set of 53 ionised monosubstituted and disubstituted cinnamamides [XC6H4CH=CHCONH2, X = H, F, Cl, Br, I, CH3, CH3O, CF3, NO2, CH3CH2, (CH3)2CH and (CH3)3C; and XYC6H3CH=CHCONH2, X = Y = Cl; and X, Y = F, Cl or Br] are reported and discussed. Particular attention is paid to the significance of loss of the substituent, X, from the 2-position, via a rearrangement that is sometimes known as a proximity effect, which has been reported for a range of radical-cations, but is shown in this work to be especially important for ionised cinnamamides. When X is in the 2-position of the aromatic ring, [M – X]+ is formed to a far greater extent than [M – H]+; in contrast, when X is in the 3-position or 4-position, [M – H]+ is generally much more important than [M – X]+. Parallel trends are found in the spectra of XYC6H3CH=CHCONH2: the signal for [M – X]+ dominates that for [M – Y]+ when X is in the 2-position and Y in the 4-position or 5-position, irrespective of the nature of X and Y. Further insight is obtained by studying the competition between expulsion of X· and alternative fragmentations that may be described as simple cleavages. Loss of ·NH2 results in the formation of a substituted cinnamoyl cation, [XC6H4CH=CHCO]+ or [XYC6H3CH=CHCO]+; this process competes far less effectively with the proximity effect when X is in the 2-position than when it is in the 3-position or 4-position. Additional information has been obtained by investigating the competition between formation of [M – H]+ by the proximity effect and loss of CH3· by cleavage of a 4-alkyl group to give a benzylic cation, [R1R2CC6H4CH=CHCONH2]+ (R1, R2 = H, CH3).

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Kinetic energy release and position of the transition state during the intramolecular substitution of ionized benzalacetones

Cited by 17 publications

References 24 publications

Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors

Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors

Freisetzung kinetischer Energie und Hammond‐Postulat bei der intramolekularen aromatischen Substitution in 2‐Stilbazol‐Ionen

Proximity effects in the electron ionisation mass spectra of substituted cinnamamides

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Kinetic energy release and position of the transition state during the intramolecular substitution of ionized benzalacetones

Cited by 17 publications

References 24 publications

Kinetic Energy Release and Position of the Transition State for С6Н7 + Ions Produced from Isomeric C7H8O Precursors

Kinetic Energy Release and Position of the Transition State for С6Н7 + Ions Produced from Isomeric C7H8O Precursors

Freisetzung kinetischer Energie und Hammond‐Postulat bei der intramolekularen aromatischen Substitution in 2‐Stilbazol‐Ionen

Proximity effects in the electron ionisation mass spectra of substituted cinnamamides

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Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors

Kinetic Energy Release and Position of the Transition State for С₆Н₇ ⁺ Ions Produced from Isomeric C₇H₈O Precursors