Mechanism of quaternization

In addition to kinetics methods linked to other techniques previously mentioned, there is a series of 12 interrelated kinetics studies which have been grouped together and summarized for brevity. Apart from a lone study on the kinetics and mechanism of quaternization of tertiary phosphines with unsaturated carboxylic acids in aprotic solvents. " These interrelated studies involve kinetics and mechanisms of anilinolysis, pyridinolysis, and benzyl-aminolysis of phosphinic and thiophosphinic chlorides, chlorophosphates and thiophosphates, etc., in various solvents including acetonitrile and dimethyl sulfoxide, referenced in any order. 

Thiazolium salts can be obtained either directly by slight modifications of ring-closure methods, already described for the parent bases, or by classical quaternization of the bases, the detailed mechanism of which have been reported in Chapter III the quaternization is best represented by a classical SNj mechanism, the solvent playing an important part (14) unless the reaction is run without any solvent. 

In analogy to the transformations observed for other compounds, a similar process was proposed for the interconversion of thiaspirane sulfoxides and to explain the dependence of the thermolytic process on sulfoxide stereochemistry. Scheme 1 shows the probable mechanism of the transformation. Stereochemical transformations of the C30 Nuphar thiaspiranes have been observed on quarter-nization of thiobinupharidine (16) (equatorial sulfur atom). The quaternized quinolizidine system is transformed from the trans to the cis form with inversion of the relative configuration of the corresponding C-7 or C-7. ... 

The Ni and Pt complexes can also be incorporated into polymer films of quaternized poly(vinylpyridine) (PVP) and deposited onto the transparent electrode (84). Photocurrents are enhanced to microamps (pA), an increase that may be attributed to either the effect of immobilization of the complexes near the electrode surface or an increase of the excited-state lifetimes in the polymer matrix. However, the effective concentrations of the complexes in this study were much greater than for the acetonitrile solutions in their earlier work. The polymer films are not stable to continuous photolysis, and voltammograms of the films are quite sensitive to anions used in the supporting electrolyte. The system can be stabilized by using a polymer blend of PVP and a copolymer containing quaternary ammonium ion and including [Fe(CN)6]4- in the electrolyte solution (85). Upon irradiation of the visible MLCT bands of [M(mnt)2]2 (M = Ni, Pt), photocurrents are produced. The mechanism (Scheme 4) is believed to involve photooxidation of the metal bis(dithiolene) triplet state by the Sn02 electrode, followed by [Fe(CN)6]4 reduction of the monoanion, with completion of the ET cycle as ferricyanide, Fe(CN)6 3, diffuses to the other electrode and is reduced. 

Uses. Tetramethylene sulfone has high solvent power for aromatics and has been used extensively by Olah and co-workers for Friedel-Crafts type nitrations and for studies of the mechanism of nitronium tetrafluoroborate nitration of alkyl-benzenes and halobenzenes in homogeneous solution. It is a superior solvent for quaternization of tertiary amines with alkyl halides, since it has a high dielectric constant and does not enter into side reactions observed with nitrobenzene and dimethylformamide. For example in the synthesis of the acridizinium salt (3), Bradsher and Parham effected quaternization of (1) with benzyl bromide in tetramethylene sulfone at room temperature in excellent yield. Several other salts analagous to (2) were obtained in good yield and in crystalline form with use of tetramethylene sulfone, whereas with other solvents the products were colored... 

Quaternary salts, isolation of, 10 Quaternization, by alkyl halides, 2-7 by aryl halides, 7-9 on carbon, 53 definition of, 2 by dimethyl sulfate, 9 electronic effects in, 11 in JV-heterocycles, 16, 38 by heterocyclyl halides, 7—9 isotope effect on, 55 mechanism of, 53-56 by methyl euyl-sulfonates, 9, 10 on oxygen, 52 rates of, 55 reagents for, 2-10 by self-condensation, 8 solvent effect on, 10, 55 solvents for, 10 steric effects on, 12, 13 substituents, influence on, 11, 19, 23 on sulfur, 51 Quinaldine, 4-amino-, 4 Quinazolines, 2-alkyl-, salt formation of, 6... 

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