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Rakhmatov Khudoyor Boboniyozovich, Associate professor of the chemistry faculty of Karshi engineering-economics institute The Republic of Uzbekistan, Qashqadaryo Region, Qarshi city Е-mail: [email protected] Kholliev Shamsiddin Khudoyberdievich, Assistant professor of the chemistry faculty of Karshi engineering-economics institute The Republic of Uzbekistan, Qashqadaryo Region, Qarshi city Е-mail: [email protected] Yuldashev Tashmirza, Head of the technological machines and equipment faculty of Karshi engineering-economics institute The Republic of Uzbekistan, Qashqadaryo Region, Qarshi city,
Farmonov Humoyun, Student of Karshi engineering-economics institute The Republic of Uzbekistan, Qashqadaryo Region, Qarshi city,
DETERMINATION OF THE NATURE OF ANODIC CURRENTS OF VINYLMORPHOLINE ANODIC OXIDATION IN NON-AQUEOUS MEDIUM
Abstract: the article demonstrates a possibility of determining the nature of anodic currents of vinylmorpholine electrolytic oxidation in non-aqueous medium. The nature of the current-potential curves of vinylmorpholine anodic oxidation taken at different temperatures of sample solution and microanode platinum disc rotation speed in all tested background electrolytes as well as solvents, was established as diffusion and by the method of log analysis its irreversible nature was established.
Keywords: palladium, vinylmorpholine, acetic acid, n-propanol, titer.
For optimization of the amperometric titration trol of the analyzed VM solution and compliances conditions of metal ions, including the other factors with some formalities. Therefore, a log analysis was that affect the shapes of the curves and the results conducted for the purpose of determination and iden-of the determination, it is also necessary to estab- tification of the reversibility and irreversibility of the lish the nature of the anodic currents of the anodic processes occurring in the solution and to establish oxidation of vinylmorpholine (from here on called the nature of the influence of the microelectrode disc VM) in mixed and non-aqueous solutions used. rotational speed and the temperature of the investi-
It is established that the nature of inherently mixed gated VM solution on the maximal current and other and kinetic currents requires strict thermostatic con- parameters of the anodic oxidation ofVM.
Log analysis of VM anodic voltameprograms
With the purpose of determining of the kinetics of the electrode processes of oxidation of VM on a microanode platinum disc in non-aqueous and mixed media, a log analysis ofVM voltamperograms obtained in a series of experiments was conducted. For each curve obtained, the value Y= lgI/Id-I was calculated for 10-15 equally spaced potential values in the area of VM wave. Then, according to the obtained values, a graph was plotted in the coordinates Y = X, where X is the value of the potential. In general, the graphs in all cases were almost rectilinear, but the tendency to tilt to the potential axis were always smaller than could be expected for a reversible process with the number of electrons participating in it, which indicates the irreversibility of the corresponding electrode process. "a" and "b" parameters were calculated on based on the experimental values ofy. and x. by using the least squares method according to the formulas:
a = Zx2Zy2 - Zx y / PZx ,2 - (Zx.)2; b = PZx y. - Zxt Zy/PZx2 - (Zx ) where P stands for the number of used values of x and y
The half-wave potentials (E^) and the product an were calculated, using the found values of the parameters "a" and "b", where a stands for the transfer coefficient, and n is the number of electrons participating in the process. Calculations were carried out according to the formulas:
E1/2 = -a/b; an = 0.0584
The number of electrons participating in the electrode reaction, determined from the slope of the straight line, is significantly lesser than the truth number-2, which was found by the coulometric method, it also indicates that the process is irreversible. On the other hand, in accordance with the logarithmic analysis of the voltammograms of the oxidation of VM on a microanode platinum disc in non-aqueous media and backgrounds, it can be concluded that in all background electrolytes (0.25M CH3COOK, 20M LiCLO4, 0.15M LiNO3) and the
investigated protolytic solutions (acetic acid and propanol) VM is completely irreversible.
VM electrolytic oxidation at different rotation speed of microanode platinum disc and temperatures of investigated solution
Electrode processes of VM oxidation in nonaqueous protolytic media, which are not followed with the formation of new phase, are extremely poorly researched. The study of those processes would make possible the fuller understanding of the laws of electrochemical kinetics. To determine the nature of anodic current of VM oxidation it was necessary to study the dependence of the maximal current on the number of rotations of the microanode disc. The research that was conducted at 25°C and various rotation speeds of the electrode (380, 725, 1085 and 1400 rpm) showed that the magnitude of the maximal current of VM oxidation is proportional to the number of rotations of the microelectrode disc. As the condition of anodic currents of the depolarizer in all the background electrolytes of the protolytic solvents is the same, the table gives the results of the effect of temperature on the magnitude of the maximal current of VM oxidation only for acetic acid media on various backgrounds. The experiments showed that when researching the dependence on the root of the square of the speed of rotation of the microanode disc of the maximal current of VM oxidation in protolytic media, all four experimental points corresponding to different electrode velocities fit very well on the line passing through the origin, which again confirms the diffusion nature of maximal current of VM oxidation on a microanode platinum disc. The detected limitation of the maximal current of the electro oxidation of the reagent by the mass transfer rate was observed for all background electrolytes studied and protolytic solvents.
The fact that was discovered by the aforementioned research makes it possible to consider that diffusion-convection equation for rotating electrode disc is usable for VM anodic oxidation speed [1-3]. The data obtained during experiment allows for the
conclusion that the rate of anodic oxidation of the re- at different background electrolytes distinct in acid-searched depolarizer in non-aqueous protolytic media base properties is limited by diffusion to the electrode.
Table 1. - Dependence of the maximal current of VM oxidation on microanode platinum disc in acetic acid media and various background electrolytes on the temperature of the researched solution
Solvent type Type and amount of background, mol/l Temperature coefficient of maximal current Temperature of researched solution, oC Maximal current value, yA
210-4M 410-4M
Acetic acid 0.25 KCH3COO 3.32 24.0 4.05 8.07
0.25 KCH3COO 3.43 30.0 4.85 9.71
0.25 KCH3COO 40.0 6.55 13.12
0.20 LiClO, 4.15 24.0 7.80 15.58
0.20 LiClO, 3.66 30.0 9.77 19.52
0.20 LiClO4 40.0 13.41 26.82
0.15 LiNO3 4.18 24.0 4.27 8.56
0.15 LiNO3 3.24 30.0 5.45 10.78
0.15 LiNO3 40.0 7.15 14.34
aqueous protolytic media used, and above 40 °C the agar-agar gel of the connecting bridge was dissolved.
By applying our research, we can conclude that the proportional relationship between the magnitude of the maximal current and the concentration of the researched VM-reagent for all the studied non-aqueous protolytic solvents and their mixtures with some inert solvents, as well as background electrolytes, is well fulfilled in the concentration range 2 -10-3 - 4 -10-5 mol/l.
It has been discovered that the polarization curves of VM oxidation, taken at different temperatures of the solution and number of turns of microanode platinum disc in all the studied background electrolytes and solvents, has diffusive nature, and its irreversible character is revealed by the method of logarithmic analysis. On the basis of polarization curves, it was established that if the process of electric oxidation of the researched depolarizer on the microanode platinum disc in the non-aqueous media is non-reversible, the electrode process is accompanied by the recoil of two electrons, followed by the transformation into simpler substances, the nature of which has not yet been identified.
Established linear relationship between the concentration of the reagent in the researched solution and the limiting current in the range of its oxidation potentials allows us to recommend the use ofVM as analytical titrants for ions of various metals in nonaqueous amperometric titrations.
The confirmation of diffusive nature of anodic currents of VM oxidation was likewise given by the determined average value of the temperature coefficient of the maximal current of oxidation at rotation speed of microelectrode disc equal to 1085 rpm in the temperature range 24-40 °C, which equals 3.0-5.6% per degree.
The temperature coefficient values of maximal anodic current of VM were calculated by using the following equations and technique [4-6]:
K = [(id )-(Id ) ]-100/(t 2 -11 )-(ld K,%
Where (Id )h - maximal current at t2; (Id ) -maximal current at t1.
Experiments were not carried out in a wider temperature range, since below 24 °C the background electrolytes that were used in research were partly deposited due to their limited solubility in the non-
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