Cation of nitrogen

Polyheteroatom Cations of Nitrogen and Sulfur. The simplest stable S—N species is the NS+ thiazyl cation.940 A convenient synthesis is the reaction of excess AgAsF6 with S3N3CI3 in SO2.941 The bond length of the NS+ cation shows a pronounced temperature dependence (corrected value = 1.42 A), and of the two resonance structures N=S+ is stabilized by ionic interactions.942... 

Combining the cationic component, usually quaternary ammonium cations of nitrogen heterocycles and inorganic or organic anions, numerous ionic liquids are... 

Primary arylamines like primary alkylammes form diazonium ion salts on nitro sation Aryl diazonium 10ns are considerably more stable than their alkyl counterparts Whereas alkyl diazonium 10ns decompose under the conditions of their formation aryl diazonium salts are stable enough to be stored m aqueous solution at 0-5°C for a rea sonable time Loss of nitrogen from an aryl diazonium ion generates an unstable aryl cation and is much slower than loss of nitrogen from an alkyl diazonium ion... 

The diazonium ion from 2 2 dimethylpropylamine rearranges via a methyl shift on loss of nitrogen to give 1 1 dimethylpropyl cation... 

The XeF+ cation forms Lewis acid—base adduct cations containing N—Xe—F linkages with nitrogen bases that are resistant to oxidation by the strongly oxidizing XeF+ cation having an estimated electron affinity of the XeF+ cation of 10.9 eV (12). The thermally unstable colorless salt,... 

Oxidation of A-aminoazetidines (19), deoxygenation of A-nitrosoazetidines (20) and direct deamination of azetidines (21) with difluoroamine leads to cyclopropanes (23) by extrusion of nitrogen from a diazine intermediate (22) (63JA97). A further interesting ring contraction occurs in the Ag" catalysed solvolysis of the A-chloroazetidine (24), which appears to involve the intermediate cation (2S) (7ITLI09). 

Almost as soon as Pedersen announced his discovery of the crown ethers (see Chaps. 2 and 3) it was recognized by many that these species were similar to those prepared by Busch and coworkers for binding coinage and transition metals (see Sect. 2.1). The latter compounds contained all or a predominance of nitrogen and sulfur (see also Chap. 6) in accordance with their intended use. The crown ethers and the polyazamacrocycles represented two extremes in cation binding ability and preparation of the intermediate compounds quickly ensued. In the conceptual sense, monoazacrowns are the simplest variants of the macrocyclic polyethers and these will be discussed first. 

The stabilizing influence in the hydrated cation is the amidinium resonance. If a solution of the cation is neutralized, a short-lived hydrated neutral molecule (4) (half-life 9 sec at pH 10) is obtained with an ultraviolet spectrum similar to that of the hydrated cation but shifted to longer wavelengths (5 m/ ). Supporting evidence can be derived from the anhydrous nature of the cation of 4-nitroiso-quinoline (pK 1.35), in which the nitro group has a similar electronic influence to that of the ring nitrogen atom N-I in quinazoline and where amidinium resonance is not possible. 

Reversible covalent hydration across C=N bonds occurs in a number of nitrogen-containing heterocycles, including pteridine and its 2- and 6-hydroxy derivatives, quinazoline (as the cation), and 1,4,6-triazanaphthalene (as the cation). Among bases giving this reaction, the neutral molecule exists predominantly as the anhydrous form, whereas the cation contains an increased proportion of the... 

Irreversible cationization of the azine-nitrogen will increase the reactivity of anionic nucleophiles at the position adjacent to the azinium moiety (71 relative to 70), in the absence of substantial... 

C. Influence of Cationization of the Azine Moiety and of Hydrogen Bonding to the Azine-Nitrogen... 

The.effect of the entropy of activation was noted above for the quaternary pyridine salts (280 and 281). In future work, it may also be found to reflect the electrostatic or hydrogen-bonding interactions in transition states of amination reactions and the effect of reversible cationization of an azine-nitrogen. Brower et observed a substantial rate difference between piperidino-dechlorinations of 2-chloropyrimidine in petroleum ether and in alcohol due partly to the higher entropy of activation in the latter solvent (Table III, lines 3 and 4). 

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