Thermal isomerisation of protonated chlorobenzene studied in the gas phase using high-energy collision induced decomposition mass spectrometry

Synthesis of protonated ferrocene isomers in the gas phase and their study by mass spectrometry

“…This tells us that the energy/entropy barriers between the different isomers are large enough that thermally induced interconversion between the isomers does not occur over the timescale of these reactions (the average lifetimes of ions in the chemical ionization reactor are 21 in the range of 10 -4 to 10 -3 s). The temperature dependences observed for the isobutane and ammonia systems are, therefore, the result of factors specific to the reaction chemistry of those systems.…”

“…This is not necessarily the case, however, as we have sometimes found, such effects can be due to a very large isotope effect. 21 In CID experiments, it is often difficult to distinguish between isotope scrambling in the parent ion, thermally induced by processes in the ion-molecule reactor, and that induced by the high energy collisional activation process, prior to its subsequent decomposition in the mass spectrometer. The only certain result is when scrambling does not occur.…”

“…9 The emphasis in our study was the use of various protonating agents with a wide range of reaction exothermicities, under controlled reaction conditions of temperature and pressure. The instrument used was also different, but which has proved useful previously (in favourable systems) in distinguishing protomers, close in structure and energy, 19,20 and following the changes in relative abundance as the proton moves from one site to another 21 as the temperature of the reaction gas is changed. The results of the present study demonstrate the independent existence and mechanism of formation of all three isomers of protonated ferrocene, which give distinctive patterns of behaviour in their CID mass spectra, depending on the reagent used and the reaction conditions.…”

“…they survive long enough to enter the accelerating region, but decompose spontaneously as they pass through the mass spectrometer. These ions were found to decompose efficiently by unimolecular reactions (19), (21) and (23,24) in the accelerating region, close to the ion source. These processes are easily determined by mapping the B,E plane 32 and following the decomposition 'trail' which connects parent ions and fragments.…”