Quaternary nitrogen cations

The first step of this reaction, decarboxylation of pyruvate and transfer of the acetyl group to lipoic acid, depends on accumulation of negative charge on the carbonyl carbon of pyruvate. This is facilitated by the quaternary nitrogen on the thiazolium group of thiamine pyrophosphate. As shown in (c), this cationic... 

Fig. 5 (a) Structure directing agent (SDA) in the synthesis of zeolite ITQ-3 N quaternary nitrogen A-I carbon atoms of SDA, l,3,3,6,6-pentamethyl-6-azonium-bicyclo[3.2.1]octane some 13C line assignments were not unequivocally possible, so these are left open the orientation of the dipole moment was calculated with a semiempirical AM-1 simulation with the origin at the center of gravity of the molecular cation (b) 13C H 27A1 REAPDOR experiment on synthetic zeolite ITQ-3. Adapted from [204]... 

The simplest intermediate of the nitrogen cation type is the nitronium ion, the active species in most aromatic nitration reactions. There is both cryoscopic and spectroscopic (Raman and infrared) evidence for its existence.802 On the other hand, it has a structure with quaternary rather than electron deficient nitrogen, a structure compatible with the centrosymmetric geometry demanded by the spectra. The Raman line at 1400 cm.-1 has been assigned to the totally symmetric vibration of the linear triatomic molecule. 

Brunelle, Chapter 5, also demonstrated that bis-quaternary salts with appropriate spacing between the quaternary nitrogens are dramatically better than mono-quaternary salts as catalysts for transfer of divalent anions, such as the di-anion of bisphenol A. Thus the ion pair formed from the di-anion and a bis-quat appears to be more easily formed and transferred than the species formed from the di-anion and two mono-quaternary cations. 

Cationic surfactants produce a positively charged surfactant ion in solution and are mainly quaternary nitrogen compounds such as amines and derivatives and quaternary ammonium salts. Owing to their poor cleaning properties, they are little used as detergents rather their use is a result of their bacteriocidal qualities. Relatively little is known about the mechanisms of biodegradation of these compounds. 

Large cations have a powerful effect on neuromuscular transmission, resulting from acetylcholine esterase inhibition and curariform activity. Examples are quaternary nitrogen, phosphorus and arsenic bases and chelate species such as the tris-(2,2 -bipyridine)iron(II) cation when it is injected intravenously. Bis(2,2, 2"-terpyri-dine)ruthenium(Il) perchlorate has about one tenth of the activity of curare182). 

Cationic surfactants have at least one hydrophobic group attached directly to a positively charged nitrogen atom. Cationic surfactants may be formed from nitriles, amines, amidoamines, or quaternary nitrogen bases. Significant literature reviews cover this subject in great detail.21-22... 

Pyrazole is a much weaker base than imidazole. Both have resonance-stabilized conjugate acids (Figure 14) but in the case of the pyrazolium cation 64 the direct linking of the quaternary nitrogens has a base-weakening effect. This additional effect also contributes to the low basicities of isothiazoles and isoxazoles (65 and 66). 

Bates noted that cationic sites in the resins are formed by conversion of the secondary amine groups to quaternary nitrogen by alkylation with the epichlorohydrin. On addition of the resin to a fiber slurry, ion exchange reactions occur that bind the resin firmly to the fiber through surface carboxyl groups. However, his work indicated that the resin... 

The acceleration of the 3-aza-Cope rearrangement of A-allylenamines through formation of a cationic quaternary nitrogen center (enammonium salt) has obvious advantages. However, direct allylation of enamines in order to form the enammonium ions is unsatisfactory, and difficult. Moreover, the rearrangement-hydrolysis product is often contaminated by the C-allylated product when an unsymmetrical allyl halide is employed... 

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