Effects of functional group interactions on the dissociation reactions of protonated amino alcohols

Abstract

The dissociation reactions of protonated amino alcohols were examined in a quadrupole ion trap mass spectrometer. Multi-stage collision-induced dissociation techniques were used to characterize the ions and their fragments and to assist in the determination of the dissociation mechanisms. In addition, semi-empirical calculations were used to rationalize the results on the basis of the thermodynamics of the reactions in question. The reaction of special interest was the double elimination of water and ammonia. For this high-energy process, it is shown that the initial deamination step is the thermodynamically favored one in most cases. The enthalpies of formation for the various precursor and product ions and also those for some of the reaction intermediates were estimated using molecular modelling and semi-empirical calculation methods. The values obtained indicated that the minimum endothermicity of the sequential deamination-dehydration reaction ranges from 209 to 460 kJ mol-' for the compounds studied here. Moreover, protonation at the amine site was found to be energetically favored by 38-192 kJ mol-' over protonation at the hydroxyl site.

Comparing differentiation of xylene isomers by electronic ionization, chemical ionization and self‐ion/molecule reactions and the first observation of methyne addition ions for xylene isomers in self‐ion/molecule reactions for non‐nitrogenated compounds

“…The base peaks in the DME CI mass spectra from the external source ITMS for these three isomers are all at m/z 119 ([M+13] + ). These [M+13] + ions can also be assigned as [M+CH] + since they are produced from the dissociations of [M+45] + complexes via elimination of one molecule of formaldehyde, according to Brodbelt's studies 12–31. In addition, the DME CI spectra obtained in the internal source ITMS (refer to Fig.…”

“…Brodbelt et al . have examined methyne addition reactions by dimethyl ether (DME) CI in a number of systems using an ITMS and have characterized the reaction product ions using collisionally activated dissociation (CAD) and isotopic labeling 12–31. Isomer discrimination for o ‐, m ‐ and p ‐xylene using metal ions has been described by Bjarnason et al 32,33.…”

Gas-phase protonation of arylalkylamines. A metastable ion study

“…We assume that protonation will occur predominantly on the amino group followed by proton transfer to the oxygen atom through hydrogen bonding, resulting in the thermodynamically favoured elimination of water as the only significant fragmentation process. 1,15,18,34 (b) For the unsubstituted phenylalkylamines the fragmentation patterns observed depend on the size of the alkyl chain. When the number of carbon atoms between the aromatic ring and the amino group is less than three, loss of NH 3 or CH 3 NH 2 is observed predominantly or exclusively, with a minor contribution, in the case of the secondary amine, of a peak at m/z 44 due to the ion CH 2 NHCH 3 .…”

Probing reactive sites for ion‐molecule reactions of anthraquinones with dimethyl ether using an external source ion trap tandem mass spectrometer and computational chemistry

“…Combined ion‐molecule reactions and tandem mass spectrometry (MS/MS) techniques for characterizing numerous organic compounds have been successfully performed by Brodbelt using a classical internal ionization ion trap mass spectrometer (ITMS) 1–21. Many studies have discussed applying these techniques to investigate structural information, product distribution, and functional group interaction in the ITMS 1–21. However, all these works were performed in a traditional internal ionization ITMS.…”

“…Two kinds of reagent ions with chemical reactivity can be produced in the ion trap: the CH 3 O=CH 2 + ( m/z 45) and CH 3 OHCH 3 + ( m/z 47) ions 1–21. These ions can form various ion‐molecular products, including [M + H] + , [M + 13] + , [M + 15] + , [M + 45] + and [M + 47] + ions, after reacting with various organic compounds, depending on the structures of those compounds 1–21. When DME reacts with electron‐releasing substituents of the compounds it produces [M + 13] + adducts via methylene addition, and with electron‐withdrawing substituents it forms [M + 15] + adducts via methyl addition reactions 3.…”