Gas-phase reaction of ethylsilylium ions with ethylene was studied by the r
adiochemical method. The reaction occurs via excited adduct C4H11Si+ which
structurally is a complex of ethylsilylium cation with ethylene. The lifeti
me of this complex is long enough for the isotope exchange between tritium
atoms of the cation and a proton of ethylene, as well as the isomerization
of ethylsilylium cation to dimethylsilylium to occur. Decomposition of the
complex results in predominant formation of labeled ethylene.