Pyridine, derivatives cation exchanger

The reaction is followed by separation of the substrate, lactose-lysine, from the product, fructose-lysine, on a cation-exchange resin (Durrum DC6A) using an isocratic mobile phase of pyridine-acetic acid-water (6 60 176, v/v). o-Phthalaldehyde derivatives were formed and detected by fluorescence. 

A pyridine derivative bearing an electron withdrawing group in the position p to the nitrogen can undergo addition with silyl ketene acetals in the presence of some ion-exchanged montmorillonite clays (e.g. equation 4.36) [148]. The nature of the cation present is vital to the activity of the catalyst. 

We can now make sensible guesses as to the order of rate constant for water replacement from coordination complexes of the metals tabulated. (With the formation of fused rings these relationships may no longer apply. Consider, for example, the slow reactions of metal ions with porphyrine derivatives (20) or with tetrasulfonated phthalocyanine, where the rate determining step in the incorporation of metal ion is the dissociation of the pyrrole N-H bond (164).) The reason for many earlier (mostly qualitative) observations on the behavior of complex ions can now be understood. The relative reaction rates of cations with the anion of thenoyltrifluoroacetone (113) and metal-aqua water exchange data from NMR studies (69) are much as expected. The rapid exchange of CN " with Hg(CN)4 2 or Zn(CN)4-2 or the very slow Hg(CN)+, Hg+2 isotopic exchange can be understood, when the dissociative rate constants are estimated. Reactions of the type M+a + L b = ML+(a "b) can be justifiably assumed rapid in the proposed mechanisms for the redox reactions of iron(III) with iodide (47) or thiosulfate (93) ions or when copper(II) reacts with cyanide ions (9). Finally relations between kinetic and thermodynamic parameters are shown by a variety of complex ions since the dissociation rate constant dominates the thermodynamic stability constant of the complex (127). A recently observed linear relation between the rate constant for dissociation of nickel complexes with a variety of pyridine bases and the acidity constant of the base arises from the constancy of the formation rate constant for these complexes (87). 

The rates of H-D exchange at the a-positions for a series of A-substituted pyridinium cations and pyridine 1-oxide derivatives in D20 at 75°C (Scheme 36) (70JA7547) correlate well with the Taft inductive parameter a, (p, = 15). A positively charged nitrogen in a ring is estimated to activate the a-position toward deprotonation and ylide formation by a factor of 1015. 

A study was made of the ultraviolet spectra of benzene, alkyl-, amino-, and nitro-derivatives of benzene, diphenyl-amine, triphenylmethane, triphenylcarbinol, and anthra-quinone adsorbed on zeolites with alkali exchange cations, on Ca- and Cu-zeolites, and on decationized zeolites. The spectra of molecules adsorbed on zeolites totally cationized with alkali cations show only absorption bands caused by molecular adsorption. The spectra of aniline, pyridine, triphenylcarbinol, and anthraquinone adsorbed on decationized zeolite and Ca-zeolite are characterized by absorption of the corresponding compounds in the ionized state. The absorption bands of ionized benzene and cumene molecules appear only after uv-excitation of the adsorbed molecules. The concentration of carbonium ions produced during adsorption of triphenylcarbinol on Ca-zeolite and on the decationized zeolite depends on the degree of dehydroxyla-tion of the zeolite. 

Gotor et al. have used imine exchange for the metal-ion-templated synthesis of N-macroheterocycles from (K,l )-cyclohexane-l,2-diamine 49 and pyridine-1,2-di-carboxaldehyde 50. In the absence of template a mixture of macrocycles ranging from the [2 -i- 2] to [6 -i- 6] products is observed in MeOH. However, the main product depended on the added cation addition of Ba led to the [2 + 2] cyclic imine 51, whereas addition of Cd resulted in almost quantitative formation of the cyclic [3 -i- 3] derivative 52 (Scheme 3.11). 

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