Gaseous [C7H8]+˙ ions: [Methylene cyclohexadiene]+˙, a stable species in the gas phase

Abstract Using collisional activation and collisional ionization spectra in conjunction with isotopic labelling and energetic data it is demonstrated that the metastable decomposition of ionized n ‐butylbenzene and 2‐phenylethanol leads to [C 7 H 8 ] +˙ ions which have the methylene cyclohexadiene structure. From appearance energies of metastable peaks a value of 960±10 kJ mol −1 was obtained for its heat of formation.