PUB - Publikationen an der Universität Bielefeld

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+C6H5CH2CH2CH2–C6H4CH3]. 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 [almost equal to] 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.