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https://doi.org/10.29013/AJT-20-3.4-46-51
Nazarov Shomurod Komilovich, intern applicant chemistry department of Bukhara Engineering Technological Institute
Olimov Bobur Bahodir, coal trainee intern applicant chemistry department of Bukhara Engineering Technological Institute Akhmedov Vohid Nizomovich, Ph.D., Associate Professor, Department of Chemistry, Bukhara Engineering Technological Institute E-mail: [email protected]
ELECTRONIC STRUCTURE AND QUANTUM-CHEMICAL CALCULATIONS OF VINYL ESTERS OF PHENOLS
Abstract. To date, methods of quantum-chemical calculations have been increasingly developed. As a result, it is possible to estimate the geometry of molecules, calculate the stability of intermediate products and transition states. In the experimental method of calculating such results for most reactions, along with a multi-stage process, there are difficulties associated with the appearance of intermediate stages and the presence of intermediate reaction products in an extremely small time.
Keywords: semi-empirical methods, RM3 and AMI, 3D-structure, hydroquinone, resorcinol, mono-vinyl ethers.
As is known, physical-chemical properties and Using methods of quantum chemistry it is pos-reactivity of molecules are related to their electronic sible to obtain data on electronic density, distribu-structure and energy features [1]. tion of electronic density, the potential fields of
The rapid development of quantum-chemical reaction and various spectroscopic calculations. calculation methods and the emergence of power- Currently, quantum chemistry techniques are the ful computer tools allowed to determine many prop- cheapest, simplest, and most versatile methods of erties of complex organic substances. Therefore, in studying the electron structure of molecules. How-quantum-chemical and molecular-dynamic research, ever, it is not possible completely abandoning tradi-in obtaining information necessary for creating cer- tional experimental methods of studying substanc-tain patterns and mechanisms of synthesis of organic es. Since traditional methods take into account all compounds, these methods ofphysical-chemical re- external factors. Due to the complex nature of the search are of particular importance [2]. substances, it is necessary to take into account the
Quantum chemistry makes it possible to explain influence of temperature, the nature of the solvent, experimental data on the reaction activity of organic catalysts, etc. [4; 5].
compounds and predict possible reactions. The basis The activity of the molecule in all reactions de-of modern quantum chemistry is the Schrodinger pends largely on its electronic structure and energy equation, which is usually solved for stationary states properties. With the development of quantum-in the adiabatic process [3]. chemical methods of computational, chemists have
the opportunity to plan experimental works and perform targeted synthesis of products.
Based on this, the electronic structure of the vinyl ethers of phenols used in the research was studied, as well as quantum-chemical calculations were carried out. The results obtained for the spatial geometry and the electron structure of phenol molecules using semi-empirical RM3 and AMI methods were summarized and illustrated by resorcinol, hydroquinone and their vinyl ethers (Fig. 1-2).
Figure 1. 3D-structure of the resorcinol molecule
Figure 2. 3D structure of the hydroquinone molecule
The distribution of charges in atoms in the molecules studied shows that the oxygen atom in the hydroxyl group of the initial material molecules has a high negative charge value. Consequently, the vi-nylation reaction under the reaction conditions studied in hydroxyphenols takes place by their hydroxyl group (Fig. 3-6).
0.1 DO
Figure 3. Charge distribution in atoms in resorcinol molecule
0.195
0.060 0.120
0.109 /
-0.101
0.156 0.101
M20 CCBD
0.195
Figure 4. Charge distribution in atoms in the hydroquinone molecule
Figure 5. Electron density distribution in resorcinol molecule
This fact indicates that the hydroxyl group in the initial material composition, due to the high electron-negative oxygen of the hydroxyl group, the electron cloud distribution is relatively dense and is the reaction center where the electrophilic reagent can be attached, due to the vinylation reaction occur in these centers. For a more detailed description of the substances and their use as a database, quantum-chemical calculations of synthesized vinyl compounds were also performed (Fig. 7-9).
The quantum chemical calculations of the substances selected for the vinylation process were studied, and the results were presented in Table 1. The electronic structure and energy properties of the selected molecules (total energy, formation energy, heat of formation, electron energy, core energy, dipole moment, and oxygen atom charge) allow analyzing the molecules of aromatic phenol and pre-determining their reaction center.
Figure 7. Distribution of electron densities in resorcinol monovinyl ester molecule
Figure 6. Electron density distribution in the hydroquinone molecule
Figure 8. Distribution of electron densities in resorcinol ether divinyl molecule
Figure 9. Distribution of electron densities in the hydroquinone monovinyl ester molecule
Table 1.- Quantum chemical calculations of the compounds used
Compounds Total energy, kcal/mole Formation energy, kcal/ mole Formation heat, kcal/ mole Electron energy, eV Core energy, kcal/ mole Dipole moment (D) Oxygen atom charge
Initial substances
Vinylacetylene -12291.9 -825.7 66.266 -36325.86 24033.95 0.1485 -
Hydroquinone -32067.66 -1523.33 -66.255 -129407.22 97339.56 0.00299 -0.456
Resorcinol -32068.86 -1524.52 -67.456 -129756.3 97687.44 1.119 -0.456
Synthesized vinyl compounds
Resorcinol mo-novinyl ether -44371.06 -2360.52 -11.48 -227953.15 183582.08 0.9639 -0.364
Resorcinol divinyl ester -56673.17 -3196.41 44.591 -341301.17 284628 1.159 -0.27
Hydroquinone monovinyl ether -44370 -2359.45 -10.42 -226372.85 182002.84 0.124 -0.358
Conclusion
Carrying out quantum-chemical calculations of initial chemicals, carrying out mathematical modeling of obtained results is important in planning chemical reactions, especially in determining technological parameters of reactions and development of technologies.
In this article, quantum-chemical calculations of used initial materials and formed compounds were carried out: the spatial 3D-structure of the molecule, the distribution of charges and electron density in
the atoms of the molecule, the total energy of the molecule, the energy of formation, the heat of formation, the energy of the electron, the energy of the nucleus, the dipole moment and the important charge of the oxygen atom were determined. Based on the analysis of the results, the scientific hypothesis is that the vinyl process is caused by oxygen of the hydroxyl group, which was confirmed by the results of experiments and based on spectral analysis. The results obtained are presented in the form of an iconogram, a diagram and a table.
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