Cationic reagent

Ionization (MS) Cation Reagent Major product ion(s) Other ions Reference... 

Aerosol C-61 Surfactant is a cationic reagent that will activate strongly the volatile solvents commonly used for removing paint. Bristle brushes and rollers, glass, porcelain, metal, plastic, and clothing have been treated successfully. 

In both this reaction and the nitration of toluene we used to make benzocaine, the reagent is a cation MeCO+ for the Friedel-Crafts and NC>2+ for the nitration. Our first choice on disconnecting a bond to a benzene ring is to look for a cationic reagent so that we can use electrophilic aromatic substitution. We know not only which bond to break but also in which sense electronically to break it. In principle we could have chosen either polarity from the same disconnection a (we actually chose) or b (we did not). 

Figure 11 Formation of a cationic olefin-containing reaction complex (right) by reaction of a zirconocene dialkyl precursor complex with a cationization reagent (left), via a highly reactive contact ion pair containing an alkyl zirconocenium cation (middle).

Since substantial amounts of free trimethylaluminium i.e. Al2Me6) are present in normal MAO preparations, cationic trimethylaluminium adducts Cp 2Zr-( r-Me)2AlMe2, in outer-sphere association with their MeMAO counteranions, are in general the dominant species in MAO-activated catalyst systems [D. E. Babushkin, N. V. Semikolenova, V. A. Zakharov, E. P.Talsi, Macromol. Chem. Phys. 2000, 201, 558]. While being quite stable against destructive side reactions MAO-activated catalyst systems are thus often less active than those obtained with the cationization reagents described above. 

Cationating reagents include alkyl halides, esters, ethers, and anhydrides. These compounds do not react with alkenes without prior ionization or activation by a Lewis or protonic acid as shown in Eq. (29). 

Electrophiles are electron-deficient, sometimes cationic, reagents that react with regions of higlier electron density within a molecule. 

Examples of the separation of cations (with an anionic reagent) and anions (with a cationic reagent) are given in Figures 13.1 and 13.2. A further example of ion-pair chromatography is shown in Figure 22.2. 

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