Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

Abstract

<jats:title>Abstract</jats:title><jats:p> The investigation of several <jats:sup>13</jats:sup>carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations. </jats:p>

Determination of branching ratios for the reactions of H3O+ with ethylbenzenes as a function of relative kinetic energy

“…The stated purities of the chemicals used were as follows: ethylbenzene, >98.0% (C 6 H 5 CH 2 CH 3 ; Wako Pure Chemicals); ethylbenzene-d 10 …”

“…(1)), a hydrogen atom migrates from the alkyl group to the ring. Isotope-labeling studies are useful for elucidating mass spectrometric fragmentation mechanisms, and CI-MS studies involving deuterium labeling of the side chain have been performed for primary alkylbenzenes [7][8][9][10]. H 2 , D 2 , CH 4 , and CD 4 CI studies of ethyl-and n-propylbenzenium ions by Leung and Harrison [7] showed that the migrating hydrogen atoms originate from all positions of the side chain for both compounds but that the positions are slightly preferred as donor sites.…”

Ion/neutral complexes generated during unimolecular fragmentation: Intra-complex hydride abstraction by tert-butyl cations from electron-rich and electron-poor 1,3-diphenylpropanes

“…Scheme 1). The third possible channel, known to occur in the dissociation of simple, preferably ␣-branched alkylbenzenes upon protonation both in the gas phase [15][16][17][18] and in solution [19,20], namely the loss of alkyl cations and, in particular, the t-C 4 H 9 + ion from protonated arenes, occurs to a significant extent only in the case the trifluoromethyl-substituted ion [13 + H] + and to minor extents also in the para-and meta-fluoro-substituted analogues [10 + H] + and [11 + H] + . This observation can be attributed to the fact that both the hydride donor ability of the C ␥ -H bonds and the basicity of the diphenylpropane in the ion/molecule complex are strongly decreased by the presence of the electronwithdrawing substituents.…”

“…From 4-phenylbenzaldehyde (3.64 g) and 4-tbutylacetophenone (3.52 g); yield 4.21 g (62%), yellow 72), 325 (28), 297 (19), 283 (100), 263 (35), 207 (20), 178 (58), 165 (15), 161 (15), 152 (18), 118 (14), 115 (12), 91 (17), 77 (16); IR (KBr), ν (cm −1 ): 3060, 29613060, , 29283060, , 28563060, , 16533060, , 15923060, , 13323060, , 12203060, , 1185found C 87.44, H 7.16.…”

Effect of protonation exothermicity on the chemical ionization mass spectra of some alkylbenzenes

“…In a more detailed investigation -Y < O ) +R+ I of the H, and CH, CI mass spectra of the Cx to Clo alkylbenzenes Harrison et a1. 4 have reported evidence that the competition between the olefin elimination reaction (1) and alkyl ion formation, reaction (2), is strongly influenced by the relative heats of reaction and, hence, is structure dependent. The present work investigates this dependence more systematically.…”