Daniela Ivón Fernández Ayala. Sexto Semestre. QFB. Ataque Nucleofílico. likes · 28 talking about this. Personal Blog. A partir de nuestros resultados, se encontró que un ataque electrofílico permite un ataque nucleofílico, entonces es necesario un segundo ataque mediante.
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This suggests the loss of an ethyl group C 2 H 5 from the original complex. The local HSAB principle has been widely used in studies on multiple reaction sites and in strong and weak atqque interactions . The nucleophilic attack at the pyridine nitrogen atom of 1 occurs via an s-cis,s-cis -conformer. It is possible to suggest that the Na atoms are substituted by Hydrogens to form 3-carboxyhydroxyp-sulfophenylp-sulfophenylazopyrazole protonated tartrazinesee Figure 3a.
This fact and its water soluble nature have caused nucpeofilico tartrazine is considered as a persistent contaminant in industrial effluents . On the other hand, Shahir et al analyzed the interaction of tartrazine with some cationic conventional and gemini surfactants . A38, Results and Discussion In order to observe systematically how the pyridine nitrogen atom acquires electrophilic nucleoilico and analyze the proposals made by Gibson et al.
The spectra were recorded from to nm. From last results is possible to suggest that an electrophilic attack to tartrazine may cause the cleavage of the azo bond. It is well known that the Fukui function ataqque determining the pin point distribution of the active sites on a molecule.
However, the accepted theories of the quantum chemistry provide advantages to analyze the reactivity of molecules. The total energy calculated was In this model, the solvent is treated as an unstructured continuum characterized only by its dielectric constant which is A variety of schemes to evaluate atomic charges has been reported.
However, to our knowledge, a determination of the global and local reactivity descriptors of tartrazine is still missing.
Accepted June 04, Cancer15 Allergy17 B ; 49 A, The condensed form of the Fukui function for an atom k in a molecule can be expressed as: Glutathione and related enzymes: O aduto formado pode ser separado do excesso do reagente por CCF, e quantificado por fluorimetria. These ACs have been used in large amounts as dyes because they may be obtained from relatively inexpensive methods. Furthermore, the electrophilic behavior of the pyridine nitrogen atom of 5 arises in the s-cis,s-cis- conformation and not in the s-trans,s-trans -geometry.
Acta, Local reactivity was evaluated through the Fukui function. Methods72 Even while 7 is stable for extended periods at room temperature, the ligand was easily deprotonated at the imine methyl group with loss of methane [7, 25].
Received April 8 thAccepted June 17 th Furthermore, evidence of participation of air moisture in the degradation process was observed. All the fully optimized geometries were characterized by vibrational frequency calculations, which showed only real frequencies.
The local HSAB principle and the DFT local descriptors suggest that nucleophilic attack at the pyridine nitrogen atom of 2,6-bis imino pyridines 1 depends fundamentally on stereoelectronic rather than on steric factors. A subsequent electrophilic or free radical attack will be necessary to cause the cleavage of the azo bond, see Figure 4b.
P OEt 3 was purified as described before. The results suggested that the solvation modifies the values of the chemical reactivity descriptors. The influence of the solvent was taken into account with the PCM model.
Halogenación de alquenos – Wikipedia, la enciclopedia libre
In this study we reveal, using the local HSAB principle and DFT local descriptors, that nucleophilic attack at the pyridine nitrogen atom of 1 depends fundamentally on stereoelectronic factors for a description of stereolectronic effects see Juaristi and Cuevas .
Last result suggests nucleofiico the azo bond on PT is the most reactive zone of the molecule. The energy values of the ionic states of tartrazine, cation and anion, were calculated by using the geometry of the neutral system.
Moreover, the bond distances were very similar to those reported in the literature . The energy difference between the gas phase and the structure in aqueous phase is Stewart Computational Chemistry, Colorado Springs.
In order to afford novel [N,N,N] ligands, Gibson et al. Within the framework of the Density Functional Theory, it is possible to define global reactivity parameters which give information about the general behavior of a molecule. All manipulations of air sensitive compounds were carried out as described in literature, 30 using serum caps, atasue tubes and glass syringes.
Halogenación de alquenos
The asseveration is corroborated in Figure 7. Last results suggest that some methods focused to degrade tartrazine must be improved in order to be applied at industrial level. Services on Demand Journal.