ION-MOLECULE REACTIONS OF [KETENE]+. AS A DIAGNOSTIC PROBE FOR DISTINGUISHING ISOMERIC ALKENES, ALKYNES AND DIENES - A STUDY OF THE C4H8 AND C5H8 ISOMERIC HYDROCARBONS

The gas-phase ion-molecular reactions of [ketene]+. with a number of isomeric alkenes, alkynes and dienes were studied by using tandem mass spectrometry. Ketene was reacted with C4H8 (but-1- and -2-ene and 2-methylpropene) and C5H8 unsaturated hydrocarbons (isoprene, penta-1,3- and -1,4-diene, pent-1- and -2-yne, cyclopentene and methylenecyclobutane) in a high-pressure chemical ionization source of a tandem mass spectrometer. The collisionally stabilized ion-molecule adducts were analyzed by use of collisionally activated dissociation (CAD) spectra. The three C4H8 alkenes were distinguishable on the basis of the distinct CAD spectra of their adducts with ketene. Similarly, the CAD data for the corresponding adducts derived from the C5H8 hydrocarbons point to different structures for the C5H8 compounds.