• June 21, 2019

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.

Author: Zolosar Kigazilkree
Country: Laos
Language: English (Spanish)
Genre: Politics
Published (Last): 23 February 2007
Pages: 466
PDF File Size: 8.8 Mb
ePub File Size: 8.60 Mb
ISBN: 537-9-56638-345-9
Downloads: 57084
Price: Free* [*Free Regsitration Required]
Uploader: Tushura

All samples analysed for 8 months were EPR silent, suggesting the presence of only Ru II after the degradation process. Figure 4 depicts a summary of our results through the schematization of possible pathways of the different attacks. Degassed solutions of the degradation product were transferred into quartz cells using teflon tubes. Allergy, 38 3 The condensed form of the Fukui function for an atom k in a molecule can be expressed as: Note that the azo bond is the most labile portion of an azo colourant according to available experimental reports which are coincident with the results obtained in the present work [].

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].

The nucleophilic attack at the pyridine nitrogen atom of 1 occurs via an s-cis,s-cis -conformer.

Nitric oxide as an activation agent for nucleophilic attack in trans-[Ru(NO)(NH3)4{P(OEt)3}](PF6)3

Barranca del Muerto No. It is well known that the Fukui function allows determining the pin point distribution of the active sites on a molecule. Gaussian atauqe, Revision A. A variety of schemes to evaluate atomic charges has been reported. Global reactivity descriptors such as ionization energy, molecular hardness, electrophilicity, and total energies were calculated to evaluate the tartrazine reactivity in aqueous and gas conditions.

Health C18 How to cite this article.

Intolerance to food colours and other additives. Moreover, a recent study, which involves photocatalyst degradation of tartrazine in waste water using TiO 2 and UV light indicates that increasing the TiO 2 concentration does not increase the rate of tartrazine degradation. Cyclic voltammograms of the degradated complex after 8 months of storage were obtained in acid aqueous solution pH 1.


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. The energy values of the ionic states of tartrazine, cation and anion, were calculated by using the geometry of the neutral system. If we consider that the nucleophilic substitution on tartrazine is carried out in an aqueous system and at acid pH values.

Methodology A starting geometry was generated using the PM6 method atqaue implemented in Mopac [62]. Supplementary data are available free of charge at http: O aduto formado pode ser separado do excesso do reagente por CCF, e quantificado por fluorimetria. Physicochemical methods include adsorption [15], electrocoagulation [16, 17], photocatalysis [18, 19], chemical oxidation and reduction [20], electrochemical treatment [21], ion pair extraction [22] while biological methods involve aerobic microorganisms.

Moreover, the bond distances were very similar to those reported in the literature [26]. Last results suggest that some methods focused to degrade tartrazine must be improved in order to be applied at industrial level.


The results indicate that the solvation process modifies the reactivity descriptors values. Concluding remarks The nucleophilic N -alkylation on pyridine is an unprecedented reaction throughout the history of chemistry, as Gibson, Gam-barotta, and coworkers have pointed out. Tartrazine has been scarcely studied from a theoretical point of view [26, 27]. According to the local HSAB principle, the softness of nuclelfilico nucleophile should be within the same range or value as nucleogilico preferred site in order to react in the studied molecule, i.

The chelation of MeLi by the pyridine and bucleofilico nitrogen atoms does not modify the electrophilic behavior of the [ NNN ] ligand; the soft nucleorilico nitrogen atom continues to be the most reactive site in the molecule for the methyl anion nucleophilic attack. De maneira geral, a MDR pode ser classificada em duas categorias: Received April 8 thAccepted June 17 th The results suggested that the solvation modifies the values of the chemical reactivity descriptors. However, to our knowledge, a determination of the global and local reactivity descriptors of tartrazine is still missing.


It was possible to observe that an electrophilic attack directly cleaves the azo nucleofliico, while nucleophilic or free radical attacks require additional attacks to cleave the same bond.

The electronic density of the phosphorus and carbon atoms nuclrofilico the phosphite ligand is also expected to decrease in the nitrosyl complex. Results and Discussion In order to observe systematically how the pyridine nitrogen atom acquires electrophilic character and nucleofiico the proposals made by Gibson et al.

The more reactive sites were 18C, 24Na and 24Na for an electrophilic, nucleophilic and free radical attacks, respectively. Motivated by the unprecedented nucleophilic attack at the pyridine nitrogen atom atxque bis imino pyridines, observed by Gambarotta et al. In order to mucleofilico the reactivity at atomic resolution, the Fukui Function was evaluated through equations How to cite this article.

If tartrazine is subject to an electrophilic attack, then a cleavage of the azo bond is expected, Figure 4a. The arbitrariness in the way of choosing the charges has been one of the principal criticisms of the condensed Fukui function approximation [44]. Accepted June 04, On the other hand, Shahir et al analyzed the interaction of tartrazine with some cationic conventional and gemini surfactants [27].

It establishes that although the softest atom in molecule A is in general the most reactive site, there may atwque other less soft sites, which may become the most reactive sites, regulated by the softness of the reacting molecule B [8, 9]. All manipulations of air sensitive compounds were carried out as described in literature, 30 using serum caps, teflon tubes and glass syringes. They reported a vibrational Jucleofilico characterization of this dye at different pH values [26].