Gas Phase Acid-Base Chemistry

Abstract

Since the discovery in 1968 that the order of relative acidities of a number of alcohols in the gas phase is the reverse of that observed in solution (1), it has been apparent that the acid-base properties of many species in the gas phase are radically different from their solution behavior. Furthermore, because the gas phase data reflect the intrinsic properties of the ions and molecules, interest in this area has grown rapidly. N ew experimental methods have made numerous measurements possible, and significant progress has been made in understanding the results of such measurements. In this review, we mention most of the topics currently receiving attention in gas phase acid­ base chemistry, and describe a few of the more interesting problems in some detail. For the most part, we discuss only reports from the recent literature (1978-1983), and concentrate on Bnmsted acid-base reactions; namely, proton transfer reactions. N ew results in thermodynamic properties (acidities and basicities) are covered first, followed by kinetic studies (rate constants and potential surfaces), and finally some important work on the transition between gas phase and solution phase proton transfer reactions.