Model 2-picoline

Despite the authors assertion that alkylated heteroaromatic compounds provide a better model for fuel-bound nitrogen than do the unsubstituted heterocycles, their pyrolytic study remains the most comprehensive look at substituted heteroaromatic chemistry, even several years later/ Kinetic studies are more common in the literature Frerichs et al. examined the reaction of the picolines with oxygen atom, while Yeung and Elrod studied reactions of HO with pyridine and its methyl- and ethyl-substituted derivatives.Both groups noted that the presence of nitrogen did not demonstrably affect the species chemistry generally, reactivity is comparable to toluene. 

A series of [V3 (/x -0)(/c -02CR)6L3]Cl04 complexes (R = Me, Et, 4-anisole L = pyridine, 4-picoline, lutidine) has been prepared as models for V-containing impurities in crude oils [49]. These complexes feature octahedral geometry around each... 

The polarographic experimental and calculated curves of complex formation with the following ligands N, Ai -bis(2-pyridyl methyl)- ,2-diaminoethane [118], picolinic acid [119], Ai-(2-hydroxyethyl)ethylenedi-amine [120], 1-hydroxyethylenediphospho-nic acid [121], and Ai-(2-hydroxyethyl)imi-nodiacetic acid [122] was used for modeling the Cd(II)-Kgand systems. The stoichiometry and stability constants of formed complexes were evaluated. The same method was used for determinations of stability constants of Cd(II) complexes with monoaza-12-crown-4 ether in aqueous solution in the presence of an excess of sodium ions [123]. 

Metal-catalysed hydrolysis of / -nitrophenyl picolinate at pH 7.5 was in the order Cu(II) > Ni(II) > Zn(II) > Co(II) > La(III). The probable mechanism is via attack by external HO- on the metal-ion complex (80).80 High catalytic activity in the hydrolysis at pH 7 of p-nitrophenyl picolinate, but not / -nitrophenyl acetate, was displayed by the metal complexes M(2-aminopyridine)2(OAc)2 (M = Zn, Ni), showing that they were good models for hydrolytic metalloenzymes.81... 

Gargas et al. (1994) employed a three compartment model describing the urinary excretion of chromium (Aitio et al. 1988) to estimate the bioavailability of chromium(III) from chromium(in) picolinate in volunteers ingesting capsules containing 400 pg. The model contained 3 compartments, a fast-exchange compartment receiving 40% of absorbed chromium with a half-life of 7 hours, a medium-exchange... 

Using these models for estimating bioavailability, distribution, and excretion, Steams et al. (1995a) predicted that chromium(III) may accumulate in the body of humans ingesting large doses of chromium picolinate dietary supplements. 

Broadhurst CL, Schmidt WF, Reeves JB, et al. 1997. Characterization and structure by NMR and FTIR spectroscopy, and molecular modeling of chromium(IH) picolinate and nicotinate complexes utilized for nutritional supplementation. J Inorg Biochem 66 119-130. 

Results. The experimental 15N isotope effect at N1 for the decarboxylation of OMP in ODCase (Scheme 1) was measured by Cleland et al. to be 1.0068.66 Comparison of this normal isotope effect with IEs measured for the model compounds picolinic acid (17) and A-methyl picolinic acid (18) led Cleland and coworkers to conclude that the normal IE observed for OMP decarboxylation is indicative of the lack of a bond order change at Nl. This conclusion was based on the following reasoning. The IE for the decarboxylation of picolinic acid (17) is 0.9955 this inverse value is due to the change in bond order incurred when the proton shifts from the carboxylate group to the N in order to effect decarboxylation (equation 2) the N is ternary in the reactant, but becomes quaternary in the intermediate, which results in the inverse IE. The decarboxylation of A-methyl picolinic acid (18) involves no such bond order change (equation 3), and the observed normal IE of 1.0053 reflects this. 

The values for the rate constant 0 are nearly the same for the mixed complexes when L = picolinate, sulfosalicylate and 8-oxyquinoline-5-sulfonate indicating and hence it appears that they fit Model 1 (i.e.) Diebler-Eigen mechanism involving a dissociative pathway. This is true in the case of lighter lanthanides. In the case of heavier lanthanides,... 

It was evident, from the separations of PGM, that their experimental CETP values were much larger compared to that for an organic analyte at identical distribution ratios. These results indicated that factors other than mass transfer and diffusion were responsible for the additional bandwidths in the case of the metal ions. The most likely factor is the slow kinetics of back-extraction of the metal ions as the forward extraction reactions are usually rapid. To test this hypothesis, 3-picoline was used as the model compound for the determination of the CPC bandwidth due to mass transfer and diffusion (CETP if), and the CETP value due to slow chemical kinetics (CETP k) was derived by expressing the experimental CETP (CETPobs) as a sum of CETP if and CETP k ... 

Table 7 lists 15 molecules [316,320,323-334] studied by a combination GED + LC NMR, which really means GED + IR + LC NMR because the conversion to an r structure always requires a knowledge of the force field. In the majority of cases, rotational constants were also used and, finally, for perfluorocyclopropene (No. 5) and y-picoline (No. 15) the highest integration of all methods was achieved GED + IR +MW + ab initio + LC NMR. Therefore, these two molecules serve as an example of the self-consistent molecular model shown in Fig. 4. 

A similar reaction, the rearrangement of m-phenylenediamine was patented by Bayer (Figure 1) [6]. In this patent, a much higher conversion and a better selectivity than obtainable with aniline was reported. Two reaction mechanisms were proposed for the aniline rearrangement reaction [3,7]. In this contribution, we will discuss this interesting reaction and report on some studies on process variables and on the reaction mechanism. As a model compound, we used m-phenylenediamine because of the higher conversion and relatively milder reaction conditions required for its conversion into 2-amino-6-methylpyridine (a-amino-a -picoline). 

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