Aromatic Substitution in the Gas Phase. A Comparative Study of the Alkylation of Benzene and Toluene with C3H7+ Ions from the Protonation of Cyclopropane and Propene

Article abstract of DOI:10.1021/ja00534a032

Gas-phase alkylaton of benzene and toluene has been used as a probe to sample the isomeric population of C3H7⁺ ions obtained from the protonation of cyclopropane and of propene, respectively, with H3⁺ ions in H2 gas at pressures from 50 to 720 torr.The reagent from cyclopropane promotes extensive (over 40percent) n-propylation, in addition to isopropylation of the arenes, on contrast to the reagent from propene that yields only traces of n-propylated products.The n-propylating reagent is identified as protonated cyclopropane, whose lifetime must exceed 10^-7 s in the gaseous systems investigated.The mechanism and the selectivity of the gas-phase alkylation are discussed and compared to relevant mass spectrometric and kinetic results.