Chemical Ionization Chemistry, Thermodynamics and Kinetics

Chemical ionization mass spectrometry (CI-MS) is a mature technique for chemical analysis that was first developed in the mid-1960s [1,2], Since the ionization process in PTR-MS is a form of Cl, it is useful to first consider some general aspects of CI-MS before considering the thermodynamics and kinetics of proton transfer. 

An attractive reason for introducing Cl was that it provided much softer ionization than the dominant ionization technique available at that time, electron ionization (El). 

the ionization of the desired molecule or molecules is achieved through reaction with an atomic or molecular ion. Various processes are possible, ranging from simple charge (electron) transfer through to chemical reactions (formation and/or the breaking 

Proton Transfer Reaction Mass Spectrometry Principles and Applications, First Edition. Andrew M. Ellis and Christopher A. Mayhew. 2014 Andrew M. Ellis and Christopher A. Mayhew. Published 2014 by John Wiley Sons, Ltd. 

In Reaction 2.5, a third body, specified as Z, is needed to remove some energy, otherwise the adduct MX + will dissociate rapidly. 

---

Chemical Ionization Chemistry, Thermodynamics and Kinetics 27 Table 2.1 Conversion factors for commonly used energy units... 

The question about the relation between the reactivity of reactants and their structure is one of the fundamental problems of chemistry. This problem as one of the main directions of chemical kinetics was formulated in the general form about 100 years ago by N.A. Menshutkin in his works on hydrolysis of esters. One of the most important directions in this area is correlation equations relating the reaction rate constant to thermodynamic and structural parameters of reactants. The first correlation was proposed by Ch. Taylor (1914) who noticed a proportionality between the ionization rate constant of the catalyst and rate constant of the catalyzed reaction. The systematic work on correlations in chemical kinetics started from the works of J. BrSnsted and K. Pedersen who, using the results of their study of the reactions catalyzed by acids ( ha) and bases ( a), proposed the equations relating the rate constants of catalytic reactions to the dissociation constants of acids ituA (1924)... 

---