Showing papers in "Annual Review of Physical Chemistry in 1968"

Ion-molecule reactions

Abstract: : The fact that ion-molecule reactions can occur in gases has been known since early in this century, but until recently such reactions excited comparatively little curiosity, and research in this field proceeded at a slow pace. The first theoretical work of relevance here appeared in Langevin's famous mobility papers of 1903 and 1905, in which he considered the clustering of molecules about gaseous ions and orbiting collisions between ions and molecules. Approximately the first half of this volume is devoted to a discussion of all the known experimental methods for making quantitative studies of ion-molecule reactions, and a critical analysis is made of the accuracy and reliability of these methods. Considerable space is then devoted to the theoretical foundations of the subject and to the various models which have been adopted in computations of reaction rates. A review is given of the measurements in the earth's atmosphere from which information on ion-molecule reactions has been deduced, and this is followed by a discussion of ion-molecule chemistry. Finally, experimental data on 230 ion-molecule reactions are displayed in tabular and graphical form. All the available data on these reactions were critically analyzed, and the best values chosen for inclusion. In many cases, in which more than one good measurement appears to have been made on a given reaction several data are presented to indicate the magnitude of the disagreements among the separate results.

Ligand Substitution Dynamics

Abstract: Substitution of a ligand in an inner sphere complex by an outside group is the most fundamental reaction in metal ion chemistry

Gas Reactions Yielding Electronically Excited Species

Abstract: One promising and popular experimental approach to the prob lem of ob­ taining more detailed mechanisms of an elementary process in gas kinetics is to determine the energy distribution in its products. The techniques of infrared chemiluminescenc e and of molecular beams provide information respectively on the vibrational energy distribution and on the translational energy and scattering angles of the products. The results of these studies, particularly when combined with calculations on the kinematic behaviour of the particles on empirical or calculated potential surfaces, yield valuable in­ formation about the interactions occurring in the transition state. These topics are well covered by the proceedings of two meetings: the Applied Optics Supplement on Chemical Lasers (1) and the Faraday Society Discus­ sions in Toronto in September 1967 (2). In reactions yielding electronically excited products, more than one po­ tential surface is involved, and kinetic studies of the associated chemilumi­ nescence can yield information about the detailed mechanism. This review concentrates on reactions where the mechanism is wel i established and pre­ ferably backed by quantitative data. For this reason, many chemiluminescent reactions postulated in the reaction zones of flames and in discharges where the reacting species cannot be positively identified are not discussed. An excellent