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Over the last 30 years, mass spectrometry and allied technologies have provided significant new insights into the intrinsic, gas phase properties of organic peroxides. In this chapter, the formation and interrogation of neutral peroxides, and their ionized analogues in the gas phase are discussed for several key classes of organic peroxides. Methods for the formation of intact, gas phase cations and anions from labile, often nonvolatile, peroxides using conventional and contemporary soft ionization techniques are described. Studies of the unimolecular dissociation of these ionized peroxides are shown to yield new understanding of energetics and bonding as well as providing diagnostic markers for the elucidation of molecular structure. The bimolecular chemistries of peroxides in the gas phase are considered in two categories: (i) reactions of ions with neutral peroxides; and (ii) the reactions of deprotonated organic hydroperoxides with neutral substrates. Advanced topics cover analytical applications of chemical ionization to the detection of peroxides and peroxyl radicals along with the synthesis of distonic peroxyl radical ions. Studies of the gas phase spectroscopy of organic peroxides that exploit the ionized forms of the peroxides are reviewed including negative-ion photoelectron spectroscopy, infrared multiple photon dissociation and action spectroscopy.

DFT (B3LYP/6-31G*) and G3//B3LYP (usually referred as G3B3 in the literature) calculations have been carried out on annular tautomers of C- and/or N-functionalized imidazoles (both the aromatic 1H- and nonaromatic 2H-) and pyrazoles (the aromatic 1H- and 2H-, and nonaromatic 3H- and 4H-). The aromaticity of 1H-imidazole and 1H- and 2H-pyrazole results in these species being more stable than their nonaromatic tautomers. However, this stability is reversed when the hydrogen on the azole nitrogen or methylene carbon is substituted by OH or by F, e.g., in increasing order of stability we find 1-fluoro-1H-imidazole <2-fluoro-2H-imidazole (<2-fluoro-1H-imidazole). These results are related to a recent report of a highly substituted imidazole that exists in the >nonaromatic> 2H-tautomeric form, and discussed subsequently in a purely thermochemical context. © 2006 Springer Science+Business Media, LLC.

The gas phase basicity and proton affinity of a molecule, M, are both defined in terms of the hypothetical reaction: M + H(+) yields MH(+). The gas phase basicity is the negative of the corresponding enthalpy change. The available data on gas phase basicities and proton affinities of molecules are compiled and evaluated. Tables giving the molecules ordered (1) according to proton affinity and (2) according to empirical formula, sorted alphabetically are provided. The heats of formation of the molecules and the corresponding protonated species are also listed. Originator supplied keywords include: Basicity; Heats of formation; Ion-molecule reaction; Proton affinity; and Proton transfer., Reprint no. 254 from Jnl. of Physical and Chemical Reference Data, v13 n3 p695-808 1984.