Ions and neutrals in the gas phase: Structure, stability and fragmentation mechanisms.

Abstract

Overview. With the advent of two new techniques, collisionally induced dissociative ionization and neutralization reionization mass spectrometry, it is possible to investigate the structure and stability of neutrals as well as ions. Fragmentation mechanisms of alkyl phenyl ethers. The metastable fragmentation mechanisms of alkyl phenyl ethers and methyl pentyl ethers have been thoroughly investigated. It has been shown that the formation of an ion/radical complex is the key step in the metastable loss of olefin from alkyl phenyl ethers and loss of methanol from methyl pentyl ethers. The alkyl moiety in an ion/radical complex between a primary alkyl cation and a phenoxy radical undergoes a rate determining isomerization to a secondary or tertiary alkyl cation at an energy above the dissociation threshold for the resulting complex. A $\beta$(H$\sp+$) is then immediately transferred from the alkyl cation to the phenoxy radical followed by dissociation to products. Assigning structures to isomeric ($\rm C\sb5,H\sb \rbrack\sp{+.}$ ions. The ten (C$\rm\sb5,H\sb \rbrack\sp{+.}$ isomers may be distinguished based on their heats of formation, low ionizing electron energy mass spectra and charge stripping mass spectra. The fragmentation mechanisms for H$\sb2$O loss from 1-pentanol and HCl loss from 1-chloropentane were determined the aid of deuterium labelling and identification of the product (C$\rm\sb5,H\sb \rbrack\sp{+.}$ ions. Collision induced ionization efficiencies of fast neutrals. The O$\sb2$ collisional ionization efficiencies of CO and CH$\sb2$=CH$\sb2$ depend on both the translational and internal energies of the neutral. The ionization efficiencies increased with increasing translational energy from 2000-5200 V as expected for ionization by the electron detachment mechanism. The ionization efficiencies decreased with increasing internal energy. The generation of stable BH$\sb3$ and BH$\sb4\sp-$ in the gas phase. The stability of BH$\sb3$, BH$\sb4$ and their deuterated counterparts BD$\sb3$ and BD$\sb4\sp-$ were studied by neutralization reionization mass spectrometry. (Abstract shortened by UMI.)