Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions

Kuck D, Mehdizadeh A (1992)
Organic Mass Spectrometry 27(4): 443-452.

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Based on the surprising observation of an intense C4H9+ (m/z 57) peak in the electron impact mass spectrum, the fragmentation of 1,1,2,2,3,3-hexamethylindan (2) was studied by mass-analysed ion kinetic energy Spectrometry of its deuterium-labelled analogues. While methyl loss from ions [2]+ occurs with high selectivity (92%) from the positions 1 and 3 without any rearrangement, ions [2 CH3]+ undergo complete equilibration of the five methyl groups as intact entities. Subsequent multi-step skeletal rearrangement of the [2 - CH3]+ ions leads to formation of tert-butyl ions and to the loss of isobutene and propene, again without concomitant hydrogen exchange. Several kinetic isotope effects and also probably a thermodynamic isotope effect associated with each of these fragmentation processes have been found and their origin is discussed. The possibility of the formation of ion-neutral complexes [t-C4H9+ C10H10] and [s-C3H7+ C11H12] is considered on the basis of the labelling and reactivity pattern.
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Kuck D, Mehdizadeh A. Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions. Organic Mass Spectrometry. 1992;27(4):443-452.
Kuck, D., & Mehdizadeh, A. (1992). Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions. Organic Mass Spectrometry, 27(4), 443-452.
Kuck, D., and Mehdizadeh, A. (1992). Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions. Organic Mass Spectrometry 27, 443-452.
Kuck, D., & Mehdizadeh, A., 1992. Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions. Organic Mass Spectrometry, 27(4), p 443-452.
D. Kuck and A. Mehdizadeh, “Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions”, Organic Mass Spectrometry, vol. 27, 1992, pp. 443-452.
Kuck, D., Mehdizadeh, A.: Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions. Organic Mass Spectrometry. 27, 443-452 (1992).
Kuck, Dietmar, and Mehdizadeh, Ahmad. “Unusual fragmentation of 1,1,2,2,3,3-hexamethylindan. Methyl group equilibration and multi-step skeletal rearrangements in the [M - CH3]+ ions prior to the formation of t-C4H9+ and other fragment ions”. Organic Mass Spectrometry 27.4 (1992): 443-452.
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