Intracluster ion–molecule reactions of Ti + with ethanol and t-butanol clusters

Abstract

A laser ablation-molecular beam/reflectron time-of-flight mass spectrometric technique was used to investigate the ion–molecule reactions that proceed within Ti +(ROH) n (R=C 2H 5, (CH 3) 3C) heterocluster ions. The mass spectra exhibit a major sequence of cluster ions with the formula Ti +(OR) m (ROH) n ( m=1–3); these cluster ions are attributed to the H elimination reactions produced by Ti + ions within the heteroclusters. The results also indicate that consecutive H eliminations by the Ti + ion can occur for up to three alcohol molecules. Isotope-labeling experiments suggest that H elimination is the dominant reaction pathway for OH bond cleavage in Ti +–alcohol heteroclusters. The TiOH + and TiO + ions observed in the mass spectra are interpreted here as arising from the insertion of Ti + ions into CO bonds, followed by alkyl radical and molecular eliminations respectively from [HOTi +R] intermediates. The experiments also show that the chemical reactivity of Ti +–alcohol heterocluster ions is greatly influenced by cluster size and by the nature of the alkyl group of the alcohol molecule. The observed reaction energetics and formation mechanisms of the heterocluster ions are also discussed.