Quaternary ammonium species

A quaternary ammonium species 1, bearing an electron-withdrawing group Z a to the nitrogen center, can rearrange to a tertiary amine 3, when treated with a strong base. This reaction is known as the Stevens rearrangement. ... 

Ring nitrogens in pyrazines and the benzo derivatives react with electrophiles to form quaternary ammonium species such as iV-alkylpyrazinium salts and pyrazine iV-oxides. N-Alkylation has generally been performed by treatment with a reactive alkyl iodide. The N-1 nitrogen in 2(l//)-pyrazinone 5 is methylated using chloro(chloromethyl)dimethyl-silane followed by desilylation with cesium fluoride to yield l-methyl-2(l//)-pyrazinone <2000TL4933>. 

Material 1 was also treated with 3-bromopropyltrichlorosilane to yield a propyl tether with a bromo-head group (4). Substitution with either trimethylamine or triethylamine to form the corresponding quaternary ammonium species, followed by ion exchange with potassium perruthenate afforded the catalytic species (5) and (6) respectively. The black solid 5 was found to be an equally efficient catalyst for the oxidation reactions and 6 was found to be a more highly active recoverable and reusable... 

Substrates susceptible to Sn 1 attack and those bearing leaving groups other than halides have also been employed in the Michaelis-Arbuzov reaction, for example, dialkyl sulfates, alkyl mesylates, alkyl tosylates, quaternary ammonium species, activated acetates as have other electrophiles, for example, alkyl fluoroborates, lactones, lactams, aziridines, sulfones, iminium cations, and orf/io-quinonoids.6,13-15,18... 

The Hofmann exhaustive methylation usually follows the anti-E2 bimolecular elimination pathway. Normally, the hydroxide anion removes the P-hydrogen and so initiates the E2 mechanism. If, however, the quaternary ammonium species is so highly hindered that this is not possible, then the hydroxide anion removes a proton on one of the methyl groups that forms part of the ammonium cation and reacts via a five-membered ring version of the Ei mechanism. 

Organoclays based on the interlayer adsorption of quaternary ammonium species are receiving increasing attention due to their ability to selectively adsorb neutral... 

Basic extractants normally consist of alkylammonium species, although for analytical applications organophosphonium or organoarsonium compounds may be used. Quaternary ammonium species as shown in Equation 1.2 or uncharged alkylammonium compounds may be used as extractants. In the latter case the presence of excess anions in the systan allows the formation of charged species as, for example. Equation 1.6 ... 

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