Cation attachment

Mass Spectrometry. Field desorption mass spectrometry has been used to analy2e PPO (179). Average molecular weight parameters (M and could be determined using either protonated (MH + ) or cation attachment (MNa + ) ions. Good agreement was found between fdms and data supphed by the manufacturer, usually less than 5% difference in all cases up to about 3000 amu. Laser desorption Fourier transform mass spectrometry was used to measure PPG ion and it was claimed that ions up to m/2 9700 (PEG) can be analy2ed by this method (180). 

However, other data such as the small difference observed in the Si NMR chemical shift (0.9 ppm upheld from TgPhg) and the absence of any measurable Si-F coupling show that the interaction between the huoride ion and the silicon atoms is small. Studies to evaluate the collision cross section of TgPhg using Na show that the cation attaches itself to the outside of the POSS cage and does not significantly distort the structure. 

The first example of SILP-catalysis was the fixation of an acidic chloroaluminate ionic liquid on an inorganic support. The acidic anions of the ionic liquid, [AI2CI7] and [AI3CI10], react with free OH-groups of the surface to create an anionic solid surface with the ionic liquid cations attached [72]. The catalyst obtained was applied in the Friedel-Crafts acylation of aromatic compounds. Later, the immobilisation of acidic ionic liquids by covalent bonding of the ionic liquid cation to the surface was developed and applied again in Friedel-Crafts chemistry [73]. 

Several different types of species are illustrated in Figure 6.1. The potassium cation (K+) at the top of the figure is separated from the soil surface by water molecules and would thus be considered an outer-sphere species. The potassium cation near the bottom of the figure is directly connected to the soil particle by an ionic charge and is therefore an inner-sphere species. Above this is an inner-sphere phosphate directly bonded to a soil surface aluminum. Also shown are potassium cations attached (inner sphere) to colloidal clay (CC) and colloidal soil organic matter (COM). Each of these is a different species. 

Saf, R. Mirtl, C. Hummel, K. ESI-MS Using Potassium Iodide in Aprotic Organic Solvents for the Ion Formation by Cation Attachment. Tetrahedron Lett. 1994, 35, 6653-6656. 

Polyethers. Polyethers such as polyethylene oxide (PEO) and polypropylene oxide (PPO) have been used for ESI-MS calibration [10,11,19]. The predominant ions for these calibrants are cation attachments, and sodium attachment is frequently observed, due to traces of sodium in solvents and glassware. The positive-ion ESI mass spectra of PEO and PPO are characterized by abundant [M + nNa]n+ and some [M + ] + species. Macrocyclic polyethers and crown ethers were also used as ESI-MS calibrants [11]. In general, nonderivatized polyethers show the following drawbacks when used as calibrations solutions (1) they are difficult to flush out of the ion source, (2) they generate complex mass spectra resulting from the presence of several different cation sources, and... 

Nonempirical quantum-chemical calculations of acetylide molecules support the ready displacement of alkali metal cations to the bridge position (87IZV2777 88IZV1335, 88IZV1339). This naturally leads to the conclusion that the polarization and deformation of the ir-electronic shell of acetylene must depend on the atomic number of the cation attached to the acetylene anion. However, the acetylene activation in the reaction with ketoximes via acetylides suggests nucleophile attack at a carbanionlike complex, which is of course a week point of the hypothesis. Nevertheless, the electrophilic assistance from the alkali metal cation (Na+) to the... 

The 4-methylcyclopropylcarbinyl [104] and the 4,4-dimethylcyclopropyl-carbinyl [105] cations have been shown by Olah et al. (1970a, 1973a,b Olah and Liang, 1975) to be stable bisected cyclopropylcarbinyl cations. Attached to the structures [104] and [105] are and (ref. CSj) chemical... 

Seven horse heart cytochrome C derivatives, each with a single sarcophaginate [Co(diAMsar)]3+ cation covalently attached to a specific surface carboxylate side chain, were synthesized. The experimental intramolecular electron transfer rate constants is nearly independent of the [Co(diAMsar)] + cation attachment site [320]. 

Under LD conditions, alkali metal cation attachment is the dominant ionization process. Protonated molecular and fragment ions are generally not... 

Bromine acts as an electrophile. The partial charge becomes a full charge and a bromine cation attaches to the double bond, leaving a Br ion behind. The cyclic intermediate is called a bromonium ion. 

Hydrogen cations attach themselves to water molecules to form hydro-nium ions, H3O+.)... 

S ], = concentration of active sites (Q) expressed as total Q per total liquid volume dy- = fraction of total number of TPC cations attached to Y anions 0 = fraction of total number of TPC cations attached to X anions. See Notation for the rest. 

Guittard, J., Tessier, M., Blais, J. C., Bolbach, G., Rozes, L., Mar6chal, E., and Tabet, J. C. Electrospray and matrix-assisted laser desorption/ionization mass spectrometry for the characterization of jxrlyesters. /. Mass Spectrom., 31,1409,1996. Deery M. J., Jennings, K. R., Jasieczek, C. B., Haddleton, D. M., Jackson, A. T., Yates, H. T., and Scrivens, J. H. A study of cation attachment to polystyrene by means of matrix-assisted laser desorption/ionization and electrospray ionization-mass sp>ectrometry. Rapid Commun. Mass Spectrom., 11, 57,1997. 

Saf, R., Mirtl C., and Hummel, K. Electrospray mass-spectrometry using potassium-iodide in aprotic organic solvents for the ion formation by cation attachment. Tetrahedron Lett., 35, 6653, 1994. 

Cation attachment is also called cationization or desolvation. In this process, cations (typically iC or Na" ) attach themselves to receptive sites on analyte molecules in the condensed phase. The combination of emitter heating and high field results in the desorption of cation attachment ions (e.g., MNa ). This mechanism is typically observed for more polar organic molecules (e.g., those with aliphatic hydroxyl or amino groups). 

Hogan, J. D. and Laude, D. A. J., "Mass Discrimination in Laser Desorption/ Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Cation-Attachment Spectra of Polymers," Anal. Chem., 64, 763-769, 1992. 

In the analysis of synthetic polymers, ionization is usually achieved by cation attachment, which is largely a matrix-independent process. 

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