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Section 7. Chemistry
Juraev Ilkhom Ikromovich, Lecturer of chemistry department of Navoiy State Mining Institute, External doctoral candidate of chemistry department of National University of Uzbekistan named after Mirzo Ulugbek, Tashkent, Vuzgorodok Е-mail: kimyo8585@mail.ru Smanova Zulaykho Asanaliyevna, Head of analytical chemistry subdepartment of chemistry department of National University of Uzbekistan, Named after Mirzo Ulugbek, Uzbekistan E-mail: Smanova.chem@mail.ru, Rakhimov Samariddin Bakhtierovich, External doctoral candidate of chemistry department of National University of Uzbekistan Named after Mirzo Ulugbek, Uzbekistan, Tashkent, Vuzgorodok
STRUCTURE AND PROPERTIES OF PYRIDILAZO-CONTAINING DERIVATIVES
Abstract: The structure and composition of the azo coupling compounds synthesized at the Department of Analytical Chemistry of the National University of Uzbekistan named after Mirzo Ulugbek have been studied. Pyridilazo-containing derivatives were studied by IR and electron spectroscopy, and analytical active and functionally active groups were identified. The optimum conditions for the complexing of copper ions (II) with synthesized reagents are determined. A photometric method for determining copper (II) in various water samples has been developed.
Keywords: copper, complex formation, structure, 4-(6-CH3-2-pyridilazo)-m-phenilendiamine.
One of the most formidable challenges to the reagents, metals and changes occurring at their com-
researchers of organic reagents synthesis is finding a plexing is necessary to resolve this problem. common principle for choosing analytical reagents Revelation of aforementioned properties should
with high selective ability and sensitiveness. Elaborate help in outlining of the main direction of synthesis study of three-dimensional and electronic structure of and physico-chemical researches aiming at obtaining
valuable analytical reagents. In the study of new synthesized reagents, complexing is studied primarily on copper ions as they have properties peculiar to them. Studied reagents were synthesized at analytical chemistry subdepartment of chemistry department of National University of Uzbekistan named after Mirzo Ulugbek.
The aim of this study is to synthesize new pyridi-lazo-containing organic reagents 4-(6-CH3-2- pyri-dilazo)-5-CH3-resorcinol (6-CH3-PAO); 4-(6-CH3-2- pyridilazo)-m-aminophenol (6-CH3-PAPh); 4-(6-CH3-2-pyridilazo)-m-phenylenediamine (6-CH3-PAPhDA); 4-(6-methyl-2-pyridilazo)-5-diethylaminophenol (PADEAPh) and finding analytical reagents with better selective properties to determine copper ions. Variation of azo coupling compound was achieved by adding analytical-active components to the structure of reagent. It was assumed that n-electronic structure of the reagents and the successive replacement of the ligand center -OH in azo coupling compound by -NH2 will radically change both the nature of the interaction and the electronic characteristics of the excited configurations and the delocalization of mobile n-electrons inside the reagent molecule and their complexes with a copper ion. As a result, synthesized azo reagents based on 6-CH3-aminopicoline are more selective and have higher analytical selectivity.
It was shown by the carried out studies that the sequential introduction of the -NH2 group (transition of resorcinol through m-aminophenol to m-phenylenediamine) ensures high selectivity of some synthesized reagents (6-CH3-PAPh, 6-CH3-PAPhDa) to copper and sets the task a comparative discussion of the electronic characteristics of the compounds formed, depending on the structure of the ligands. The synthesis was carried out through a series of successive steps, described in the literature [1]. The yield of reagents was 70-75%. After air drying, 6-CH3-PAO and 6-CH3-PAPh have become dark-brown powders and 6-CH3-PAPhDA - resinous substance. Purified by repeated reprecipitation from
absolute alcohol, 6-CH3-PAPhDA was analyzed for carbon, hydrogen and nitrogen content, while the calculated values correspond to experimental values [2]. All synthesized reagents are readily soluble in alcohol, acetone, dimethylformamide and poorly soluble in water and diethyl ether. The individuality of all azo compounds was proved by thin layer chromatography in the butanol-hydrochloric acid-water system (100:15:27) [3].
To study the structure and composition of the azo compounds, the infrared spectra (IRS) of the reagents were recorded on the «Avatar system 360 FT-IR» spectrometer produced by Nikolet (USA) using the method of sample pressing with potassium bromide.
In the area of3000-3600 cm-1 of 6-CH3-PAO in IRS a very wide intensity related to the valence vibration of the associated -OH group is visible. Intensity in the area of 1100cm-1 is the deformation vibration of phenolic hydroxyl. The group of intensities in the area of 1500, 1600 cm-1 is the stretching vibration of -C=C-, -C=N-, -N=N-, in the molecule of reagent. Comparison of 6-CH3-PAPh IS and 6-CH3-PAO IS revealed that 6-CH3-PAPh spectrum in the area of 3000-3600cm-1 has two intensities of -OH and -NH2 primary groups. Changes of intensity form of 6-CH3-PAPh is attributed to -NH2 primary group. Other intensities in 1500, 1610 cm-1 are similar to intensities of 6-CH3-PAO reagent [4-6].
However, in 3000-3600 cm-1 area of 6-CH3-PAPhDA instead of one wide intensity zone, as in 6-CH3 -PAO spectrum, a split of intensity in 3200, 3330, 3380, 3490 cm-1 areas was found, attributed to symmetrical and asymmetric valence vibrations of the primary -NH2 group. Therewith, 1100 cm-1 area lacks intensity attributed to deformation vibrations of-OH group at 6-CH3-PAO and 6-CH3-PAPh reagents [6].
To determine the existing forms of synthesized azo reagents in aqueous solution, the light absorption spectra of the reagents were taken from the acidity of the medium: in 10%, 2 n, 0.1n H2SO4, pH=7 and 0.1 n NaOH on SF-46 from 210-600 nm. Analysis of the light absorption spectra of azo reagents shows
the bathochromic shift of the light absorption maxima attributed to different dissociation of the reagents depending on the acidity of the medium. In neutral and weak-alkaline media, the reagents are in a more reactive ionic state. Consequently, 6-CH3-PAO and 6-CH3-PAPh reagents interact with many metal ions to form brightly colored complex compounds. Apparently, the replacement of one -OH group by -NH2 group (transition from 6-CH3-PAO to 6-CH3-PAPh) is almost unseen in qualitative terms. Yet, the replacement of both hydroxyl groups by -NH2 sharply increases the selectivity and reduces the number of interacting ions (transition from 6-CH3-PAPh to 6-CH3-PAPhDA). Due to its selective properties 6-CH3-PAPhDA reagent was used in the analysis of copper and cobalt in standard samples of steels, soils, donor blood and polymeric metal complexes, the results of which were published in [7-9].
The electronic structure of this azo reagent confirms that 6-CH3-PAPhDA interacts only with cobalt, palladium and copper ions. The use of this reagent made it possible to apply the developed methods for photometric determination of copper [10].
Determination of copper content in industrial sample
Developed photometric method for determining copper with 6-CH3-PAPhDA reagent turned out to
References
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Method of determination: a certain amount of sample solution, 2.0 ml of a 0.1% of 6-CH3-PAPhDA reagent solution, 10 ml ofuniversal buffer solution were placed in a measuring cone with a capacity of 25 ml, adding masking agents (F- 1:800, CH3COO- 1:200) and the volume was brought to the mark with distilled water. Optical density was measured on «KOK-2» photoelectric colorimeter at l=1 cm relative to the blank test solution.
The obtained test results of M-138-2 sample, containing Cu 89.820% and their mathematical processing showed that the relative standard deviation does not exceed 0.0148; the relative error is 0.84%, and developed photometric method for determining copper (II), is characterized by high accuracy, selectivity and low boundaries of the concentrations determined.
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