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Eur. J. Mass Spectrom. 1, 445 - 455 (1995) |
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Regioselective hydride abstraction and proton transfer in gaseous ion/molecule complexes: methyl substituent effects on the fragmentation ofprotonated 1-(4-tert-butylphenyl)-3-phenylpropanes | ||
Carsten Matthias, Katrin Weniger and Dietmar Kuck* |
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ABSTRACT: | ||
Gas-phase protonolysis of 1-(4-tert-butylphenyl)-3-phenylpropanes bearing a methyl substituent at one of the arene rings gives rise to competing losses of isobutane and isobutene via intermediate, purely hydrocarbon, ion/molecule complexes [Me3C+C6H5CH2CH2CH2C6H4CH3]. The hydride transfer within the complexes occurs preferentially from the CH2 group of the methylated benzyl unit (in the order p-CH3 >m-CH3 > o-CH3 ~ H) and irrespective of the ring from which the tert-butyl group has been released originally. The reciprocal proton transfer gains importance with increasing proton affinity of the substituted benzene nucleus (p-CH3< o-CH3 < m-CH3), again independent of the original substitution pattern. Thus, the reactivity of thetert-butyl cation within the complex (as a Lewis and a Brønsted acid) is governed by the whole of the electrostatically bound 1,3-diarylpropane neutral. | ||
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