Negative ion chemistry

Negative ions are observed below typically 70-80 km altitude, where the air density is sufficiently high to enable the attachment of electrons to oxygen molecules. A complex set of reactions leads to the formation 

The first studies of the ionosphere using radiowave techniques demonstrated that electrons are nearly absent below 65 or 70 km during the day and 75 or 80 km at night. However, electrical neutrality requires a balance between charged particles. The observation of positive ions implies that equal quantities of a negatively charged particle must be present. 

Johnson et, al. (1958) performed the first observations of negative ions, and suggested that the most abundant negative ion in the D-region is 

J at mass 46. Since that time, only a very few measurements have been performed. Narcisi et al. (1971) and Arnold et al. (1971) observed the D-region at night. The presence of a transition zone above which the concentration of negative ions rapidly decreases was established by observation but the altitude of this layer seemed to vary considerably with time (Arnold and Krankowsky, 1977 Arnold, 1980). 

The chemistry of negative ions has been intensively studied in the laboratory since the 1960s by Ferguson and coworkers. A schematic diagram of the suggested chemistry resulting from their experiments is 

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The negative ion chemistry is equally clear. N07(HNOO ,(HiO) ions are fomied rapidly. Only acids, HX,... 

Wisemberg J and Kockarts G 1980 Negative ion chemistry in the terrestrial D region and signal flow graph theory J. Geophys. Res 85 4642-52... 

Gas-phase reactions which result in nucleophilic displacement at a saturated, or an unsaturated, carbon centre have been observed in positive and negative ion chemistry. By far, the most widely occurring case is the formal analog of the Sn2 reaction initially reported by Bohme and Young (1970). The experimental determination of rate constants for SN2 reactions has received a great deal of attention as has the mechanistic point of view including the interpretation of the potential energy surface for the gas-phase reaction. 

A study of gas-phase negative-ion chemistry of Lewis acid-base complexes of BH3 with Me2S, Me3N, Me3P, and Et3N has shown that the a-CH acidities in the complexes (to form dipole-stabilized carbanions) are up to 20 kcal mol-1 higher than in the uncomplexed molecules.150... 

It has been very difficult to limit the scope of this review. After some consideration, chose to divide it into sections in close correspondence with the tradition of text books in physical organic chemistry. I also decided to concentrate on literature from the last decade, although it has been necessary to cite classical papers of the field for the sake of completeness and to give an overview. I have to admit that I have chosen to focus on the literature of positive ion chemistry rather than that of negative ion chemistry, since excellent reviews have been published on that subject recently [1-3]. 

In this review we focus both on major developments in new mass spectrometric techniques and on novel chemical applications of existing mass spectrometric techniques that have been reported since 1990. Emphasis is given to the application of these techniques to the study of bimolecular ion/molecule reactions, radiative association, and dissociative recombination of positive ions. Particular attention is given to the emerging field of interstellar metal-ion chemistry and recent studies of fullerene-ion chemistry and the influence of charge state on this, and related, chemistry. Mass spectrometric studies of the photochemistry of interstellar ions are briefly considered as is interstellar negative-ion chemistry. We conclude with a brief description of the use of mass spectrometry to examine interstellar material that has made the long journey to our solar system. 

Figures 4 and 5 present model calculations for a Montana Rosebud coal-fired, potassium carbonate seeded combustor operated under slightly fuel-rich conditions (equivalence ratio = 1.09). Note that KPO2 and KPO3 are the dominant neutral phosphorus species at all temperatures. Negative ion chemistry is dominated by PO2 and PO3 below 2000 K, phosphorus species negative ions outnumber free electrons. The only negative ion which Is comparable in concentration to PO2 is Fe02 and then only at the upper temperature range. The sharp temperature falloff of Fe02 Is caused by the stability of condensed Iron containing species.

Figure 7.27. Schematic diagram of the negative ion chemistry of the D-region. From Ferguson (1979).

Fritzenwallner, J., and E. Kopp, Model calculations of the negative ion chemistry in the mesosphere with special emphasis on the chlorine species and the formation of cluster ions. Adv Space Res 21, 891, 1998b. 

Positive and negative ion chemistry of silicon-containing molecules in the gas phase ... 

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