Nitrosonium Ion NO -Induced Reactions

The solid superacidic Nafion-Hhas also been found to catalyze effectively nitration reactions with various reagents.503 The nitrating agents employed were n-butyl nitrate, acetone cyanohydrin nitrate, and fuming nitric acid. In nitric acid nitrations, sulfuric acid can be substituted by Nafion-H and the water formed is azeotropically removed during the reaction (azeotropic nitration).503 

Generally, nitration of aromatic compounds is considered to be an irreversible reaction. However, the reversibility of the reaction has also been demonstrated.506 9-Nitroanthracene and pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of HF-SbF5 as well as Nafion-H [Eq. (5.193)]. 

Nitrosonium ion (NO+) is the electrophilic species formed from nitrous acid media, which is responsible for such reactions as diazotization of amines. Nitrosonium ion has 

Similarly, NO+ is also capable of halogen abstraction from alkyl halides.513 514 In the presence of a suitable oxygen donor such as dimethylsulfoxide, nitrosonium ion can act as a nitrating agent493,494 [Eq. (5.194)]. 

Nitrosonium ion can also act as a mild and selective oxidizing agent. It has been used to cleave oxidatively oximes, hydrazones,498 and thioketals to their corresponding carbonyl compounds,499 to cleave benzylic esters515 [Eq. (5.195)], and to oxidize O-tributylstannyl and (9-trimethylsilyl ethers and benzylic alcohols516 [Eq. (5.196)]. 

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