Alkali Metal Ion in the Gas Phase

The thermodynamical studies of alkali-ion metal-molecrrle reactions in a HPMS began in the mid-1960s. Kebarle reported the gas-phase reaction involving the clustering of water molectrles around the potassirrm ion [37]. They established the thermodynamics on the solvation of iorts [38]. The study of dynamics (reaction rate) is also important in ion-molecule association, which is detailed in the Chaps. 2 and 3. These two different areas of interest can in practice be investigated using MS and computational techniques. 

A+ and represent the respective measttred ion intensities. The neutral reactants, B and D, are present in great abtmdance compared to the ionic reactants, and therefore, the ratio [D]/[B] can be asstrmed as tmchanged after eqtrihbrittm is established. 

The BDEs of ion-molecnle association complexes are afforded by enthalpy changes of the reaction 

The term ion affinities is a quantity defined at a finite temperature, usually 298 K. The principal instruments that have produced information on the bonding in ion-molecnle association complexes include HPMS, FA, ICR, and so on. 

Most ion/molecule equilibrium studies have been devoted also to the derivation of extensive scales of BDEs. From the temperature dependence of the equilibrium constants (Van t Hoff equation), enthalpy changes have been obtained. The BDEs are defined as the standard enthalpy changes at 0 K for the reaction (Eq. 1.6). These can be calcnlated using Kirchhoff s equation  

---

Cerda BA, Wesdemiotis C. Zwitterionic vs. charge-solvated structures in the binding arginine to alkali metal ions in the gas phase. Analyst. 2000 125 657-60. 

---