Onium ion salts

As discussed in Chapter 1, many electrophiles are stable in solvents and the presence of substances of moderate Lewis basicity. Even relatively strong electrophiles can be generated and handled under appropriate conditions.1 A wide variety of electrophilic carbocationic and onium ion salts have been prepared and characterized by spectroscopic methods, X-ray crystallography, kinetic studies, and other techniques. Several types of these electrophilic salts are even available commercially (such as varied onium, iminium, and carbocationic salts, etc.). Electrophiles are generally generated by the reactions of suitable precursors with Brpnsted or Lewis acids. They can be sometimes isolated, but for synthetic conversions they are more often generated in situ and reacted directly with nucleophilic reagents. 

Recently Olah and associates [91], [40c] obtained 5- and /V-nitrito onium ion salts (31) and (32), and found them to be electrophilic nitrating agents ... 

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