Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions

Mormann M, Kuck D (1999)
JOURNAL OF MASS SPECTROMETRY 34(4): 384-394.

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1,3,5-Cycloheptatriene (1) and various 7-alkyl-1,3,5-cycloheptatrienes (3, 6, 9, 13, and 16-19) were subjected to gas-phase protonation under Cl(CH4) and Cl(iC(4)H(10)) conditions and the MIKE spectra of their [M + H](+) ions were measured Loss of CH, from the parent ion [1 + H](+) and almost exclusive loss of C2H4 from the methyl derivative [3 + H](+) indicate ring contraction of the dihydrotopylium ions to protonated toluene (toluenium ions) and protonated ethylbenzene (ethylbenzenium ions), respectively, prior to fragmentation. With increased exothermicity of protonation, ions [3 + H](+) also isomerize to xylenium ions. Similarly, higher protonated n-alkylcycloheptatrienes undergo skeletal isomerization to the corresponding "chain-elongated" (n + 1)-alkylbenzenium and to the corresponding n-alkyltoluennium ions. Starting with ethyldihydrotropylium ions, a competing isomerization channel is opened giving rise to expulsion of C2H4 from the constituents of the seven-membered ring, as evidenced bg deuterium labelling and an unusually high kinetic energy release, Isoalkyl analogues behave in a similar manner with increased hydrogen exchange between the alpha position of the side chain and the ring. Copyright (C) 1999 John Wiley & Sons, Ltd.
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Mormann M, Kuck D. Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions. JOURNAL OF MASS SPECTROMETRY. 1999;34(4):384-394.
Mormann, M., & Kuck, D. (1999). Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions. JOURNAL OF MASS SPECTROMETRY, 34(4), 384-394.
Mormann, M., and Kuck, D. (1999). Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions. JOURNAL OF MASS SPECTROMETRY 34, 384-394.
Mormann, M., & Kuck, D., 1999. Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions. JOURNAL OF MASS SPECTROMETRY, 34(4), p 384-394.
M. Mormann and D. Kuck, “Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions”, JOURNAL OF MASS SPECTROMETRY, vol. 34, 1999, pp. 384-394.
Mormann, M., Kuck, D.: Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions. JOURNAL OF MASS SPECTROMETRY. 34, 384-394 (1999).
Mormann, Michael, and Kuck, Dietmar. “Protonated 1,3,5-cycloheptatriene and 7-alkyl-1,3,5-cycloheptatrienes in the gas phase: Ring contraction to the isomeric alkylbenzenium ions”. JOURNAL OF MASS SPECTROMETRY 34.4 (1999): 384-394.
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