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Zastosowanie spektrometrii masowej cyklotronowego rezonansu jonowego do badania reakcji przeniesienia protonu w fazie gazowej

Raczyńska E.D.

Wiadomości Chemiczne

1998

[Z] 52, 5-6

385-403

The principle of ion cyclotron resonance (ICR) reported in 1930 by Lawrence et al. [9] was firstly applied in mass spectrometry by Hipple, Sommer and Thomas in 1949 [26]. Their instrument has never been commercilized due to several problems with electronics and vacuum. Next instrument constructed by Wobschall et al. In the 1960s [27] had more chamce. It was modified by Llewellyn [28] in cooperation with Baldeschwieler et al. [29] and became a commercial Varian mass spectrometer in the late 1960s. Its drift cell contained three separated regions: ion source, analyser and ion collector. Important modification in ICRMS was proposed by McIver in 1970 [10a, b]. He introduced a one region trapped-ion analyzer cell and pulsed mode of operation. First FT-ICR experiments were carried out by Comisarow and Marshall in 1974 [11]. They also applied a one region trapped-ion analyzer cell. The pulsed mode of operation in the one region cell was combined with Fourier transform techniques in first commercial Nicolet FT-ICR mass spectrometer. From this moment the FT-ICR mass spectrometry has become more attractive and more frequently used by chemists. Since ions may be trapped for extended periods prior to detection in an ICR cell, both, ICR and FT-ICR mass spectrometry have been used to the study of gas-phase ion-molecule reactions [1-6]. First experimental gas-phase data of sufficient precision obtained by ICRMS became available from the 1970s for the proton-transfer reactions [2, 7, 8, 10, 41-43]. Relative acidity (DGA) or basicity (DGB) determinations were based on measurements of the equilibrium constants of proton exchange between two anions (A-1 and A-2) or two bases (B1 and B2) [7, 8, 13a]. These reactions have been studied in order to determine intrinsic gas-phase acidities or basicities of compounds and to establish general gas-phase acidity/basicity scale. Presently there are few thousands gas-phase data compiled in this scale by Lias et al. [50]. The upper limit of the GB scale is separated from the lower limit of the GA scale by ca 150 kJ/mol (Fig. 6), and thus spontaneous neutralization reactions between neutral acids and bases can not yet be observed in the gas phase.