Typical ions

Some ions are typical of given structures. Note first that compounds containing hydrocarbon chains give rise to a series of ions distant from each other by 14 Da (-CH2-). The mass where they appear depends on the group(s) that is (are) linked to them. Entirely saturated hydrocarbon ions appear at masses 15, 29, 43, 57, 71, 85, 99 Da, and so on. 

Molecules with a benzene nucleus often yield a phenylium ion at m/z 77, accompanied by a fragment corresponding to acetylene loss at m/z 51. If an alkyl chain is bonded to the benzene nucleus, ions are observed at m/z 91, which are a mixture of benzylium and tropylium structures, which produce a fragment observed at m/z 65 by losing acetylene. 

Trimethylsilyl derivatives are commonly used in GC/MS. When the molecule contains a hydroxyl, it fragments and yields (CH3)3Si+, at m/z 73, and (CH3)2Si+-OH, at m/z 75. When the molecule contains more than one (CH3)3SiO- group, an ion with mass 147 Da is systematically observed in the spectrum, even though both groups are remote from one another. This ion has the structure shown below. It is derived from the fragmentation of a complex between the ion (CH3)3Si+ and the neutral remainder of the molecule  

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Solid-State Lasers. Sohd-state lasers (37) use glassy or crystalline host materials containing some active species. The term soHd-state as used in connection with lasers does not imply semiconductors rather it appHes to soHd materials containing impurity ions. The impurity ions are typically ions of the transition metals, such as chromium, or ions of the rare-earth series, such as neodymium (see Lanthanides). Most often, the soHd material is in the form of a cylindrical rod with the ends poHshed flat and parallel, but a variety of other forms have been used, including slabs and cylindrical rods with the ends cut at Brewster s angle. 

Typical ion sources employ a noble gas (usually Ar). The ionization process works either by electron impact or within a plasma created by a discharge the ions are then extracted from the region in which they are created. The ions are then accelerated and focused with two or more electrostatic lenses. These ion guns are normally operated to produce ions of 0.5-10 keV energy at currents between 1 and 10 pA (or, for a duoplasmatron, up to 20 pA). The chosen spot size varies between 100 pm and 5 mm in diameter. 

Cluster ions are also emitted from organic materials their identity and yield depend on the chemical structure of the materials. Molecular or quasi-molecular ions may be observed as well as other ions that are formed by fragmentation, rearrangement, decomposition, or reaction [52], Several typical ion formation processes are summarized in Table 3 [40]. 

Scheme 2.2-1 Typical ions making up ionic liquids, ordered according to their...

The common tripositive cations may be separated from many dipositive cations by the basic acetate or basic benzoate method. These separations are based upon the fact that the equilibria for the first dissociation of the typical ions are ... 

A volume measure of the permitted flow rate of water through ion exchange resins and sometimes other media, such as sand. Typically, ion-exchange resins used for water softening will tolerate 8 to 40 BV/hr. 

FIGURE 1.57 The typical ions formed by the heavy elements in Groups 13/III through 15A/ show the influence of the inert pair—the tendency to form compounds in which the oxidation numbers differ by 2. 

The kinetic ion energy flux, (efimax, which is typically 20 W m - [163, 301], will raise the substrate temperature by only a few degrees. Therefore, the influence of ions will be limited to the vicinity of impact. Furthermore, typical ion energies are below the sputtering threshold of silicon [134]. 

Typical ion-pairing reagents are, for cations, alkyl sulphonic acids, eg pentane, hexane, heptane or octane sulphonic acid, and for anions, tetrabutylammonium or dibutylamine ammonium salts. In ion-pair chromatography the retention of solutes can be controlled in a number of ways ... 

Table 4.4 Typical ion-association extraction systems System...

Table 2.4. Typical ion flight times in different types of mass spectrometers...

Sensor A device having a response (ideally) for one particular analyte. Poten-tiometric sensors are typically ion-selective electrodes, while amperometric sensors rely on Faraday s laws. 

Scheme 3.8 represents a typical ion-radical mechanism of the so-called vicarious nucleophilic substitution of hydrogen as it was described by the pioneering chemist M kocza (M kocza 1989) in his summarizing review. ESR studies of other heterocyclic systems in conditions of the hydrogen-to-nucleophile vicarious substitution were reported by the research group at the Siberian branch of the Russian Academy of Sciences (Donskaya et al. 2002, Vakul skaya et al. 2005, 2006, Titova et al. 2005). 

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