RESUMO
The ion-molecule reactions of mixtures of trimethylaluminum and methylamines, to serve as a model system for group 13-15 semiconductor fabrication, were examined by using Fourier transform ion cyclotron resonance mass spectrometry. Sequential ion-molecule reactions leading to formation of multiple adduets were observed for each of the reactant mixtures investigated. Collision-induced dissociation was used to probe the adduct structures. There is evidence for hydrogen bonding between the amines and aluminum in most of the adducts studied. Rearrangement of the aluminum/nitrogen skeletons was not observed, although the aluminum/nitrogen bonds appear to be relatively strong, so that stable adducts can be formed. The monomethylamine and dimethylamine readily produce gas-phase neutral adducts with trimethylaluminum, which can be related to the basicities of the methylamines.
RESUMO
Data on the low-temperature (< 200 K) dependence of the kinetics of chemical reactions are of great importance for understanding the composition of planetary atmospheres (as well as interstellar clouds). To date such studies have been relatively rare but the situation is beginning to change. During the past 10 years a number of experimental instruments have been designed to address this problem. These instruments rely on either cryogenic or supersonic cooling, and both methods have been applied to the study of neutral-neutral or ion-neutral reactions. We briefly review these different techniques, with an emphasis on the CRESU method, and provide examples of the types of reactive systems that have been studied, with particular attention to those relevant to the atmosphere of Titan. The perspectives for future work are also evoked.