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Computational Study of protonation of ozone © Quyen Quy Ngo, Alexander Yakovlevich Samuilov, Yakov Dmitruevich Samuilov, Fanis Faritovich Valiullin, Eugenii Ivanovich Grigoriev and Alexander Alexsandrovich Petukhov Department of Technology of synthetic rubber. Kazan National Research Technological University. Karl Marx, 68. Kazan, 420015. Tatarstan Republic. Russia. Тел.: (843) 231-42-14. E-mail: [email protected] Keywords: ozone, quantum chemistry, B3LYP, protonation, DFT Abstract The process of protonation of ozone in the singlet and triplet states was studied by quantum-chemical method B3LYP / 6-311 ++ G (df, p). It was studied the geometric structure of the products of protonation. The thermodynamic parameters of protonation reaction of ozone in the singlet and triplet electronic configuration was described. It was shown that the process of protonation of ozone in all cases is exothermic and proceeds with a decreasing of free energy and with decrease of entropy. Introduction Ozone is widely used in different industries, medicine and life [1, 2].We have conducted laboratory studies on cleaning of heavy sewage of petrochemical plants, are currently being fired by recycling. When this was done the technical and economic assessment of energy costs on the disposal. Was shown the economic feasibility of the use of technological methods of separation of aromatic hydrocarbons contained in the effluent from the subsequent use of ozonation technology for final cleaning directed recycled water. In the course of research of ozonation was experimentally found anomalous change in pH from 6.7 to 18 by passing the ozone-oxygen mixture through distilled water [3, 4]. In discussing of the observed phenomena, it was hypothesized that the pH of distilled water is increased not only due to the formation of negative ions in the interaction of ozone with water, but also due to ash from the reactor of protonated ozone [4]. The concentration of hydroxide ion is increased, and the pH of the medium increases. The existence of protonated ozone previously been proven by computational methods and confirmed experimentally by several researchers [5, 6]. However, for the calculation were used outdated methods. This is not allowed reliably reason about thermodynamic stability of protonated ozone. The purpose of this issue is the thermodynamic estimation of protonation reaction of ozone. Experimental part Quantum chemical calculations were carried out using the program Gaussian09 [5]. Optimization of geometrical parameters of molecular structures was carried out using a threeparameter exchange-correlation functional B3LYP and the basis set 6-311 ++ G (d, p). To confirm that the structures are minima on the potential energy surface, and to determine the zeropoint energy at the same theoretical level were calculated vibrational frequencies. Application of the method B3LYP is suitable for studies of most organic reactions [6, 7]. Standard enthalpies of formation and the Gibbs free energy in the gas phase (T = 298.15 K, p = 1 atm) are derived from the zero-point energy, as well as the corresponding-thermal corrections to the electron energy. Results and discussions Early studies [8] have shown that ozone can have singlet and triplet electronic structure. We have made calculations of the geometric characteristics of the protonated forms of ozone with singlet and triplet electronic structure. Protonated ozone with singlet electron configuration has 4 minimum on the potential energy surface. Fig. 1 shows the ball-rod structure of protonated ozone with singlet electron configuration corresponding to the minima on the potential energy surface. Ia Ib Ic Id Fig. 1. Ball-rod structures of protonated ozone with singlet electron configuration, obtained by B3LYP / 6-311 ++ G (df, p) As can be seen from Fig. 1, all forms of protonated ozone singlet electron configuration are flat. In the first two cases, in the proton is trans- (structure 1a) and cis- (structure 1b) position with O-O bond of ozone. Oxygen-oxygen bonds in ozone are unequal. Calculated dipole moment of ozone is 0.69 D; dipole moment of the structure Ia is 11.84D, structure Ib 12.08D, structure Ic 9.89 D, the structure Id 1.39D. The third and fourth minima are structures of protonated ozone in which the proton is coordinated to the second oxygen atom of ozone (structure Ib) and all three atoms of oxygen, respectively (structure Id). Table. 1 shows the thermodynamic parameters of protonation reaction of ozone with singlet electron configuration. Table. 1. Thermodynamic parameters of ozone protonation reaction with singlet electron configuration Structure ΔGr, kJ/mol ΔHr,kJ/mol ΔSr, J/(molK) Ia -89.7 -110.2 -68.9 Ib -95.0 -113.6 -62.5 Ic -77.4 -98.6 -71.0 Id -389.0 -419.4 -101.9 As can be seen from Table. 1, all the reactions are exothermic and have large negative entropy of the reaction. Most favorable, from the thermodynamic point of view, is formation of structure Id, in which the proton is coordinated by three oxygen atoms. All the above reactions proceed with a decrease of free energy. As has been shown previously [8] ozone could have triplet electronic structure, i.e. the biradical. Protonated ozone with triplet electron configuration also has 4 minimum on the potential energy surface. Fig. 2 shows the ball-rod structureы of protonated ozone with triplet electron configuration corresponding to the minima on the potential energy surface. IIа IIb IIc IId Fig. 2. Ball-rod structures of protonated ozone with triplet electron configuration, obtained by B3LYP / 6-311 ++ G (df, p) As can be seen from Fig. 2, the structure IIa is flat. In structures IIb-d the proton not lie in plane of oxygen atoms. Table. 2. The thermodynamic parameters of protonation reaction of ozone with the electron configuration of triplet Structure ΔGr, kJ/mol ΔHr, kJ/mol ΔSr, J/(molK) IIa -169.7 -188.1 -61.8 IIb -204.3 -71.6 -225.7 IIc -176.9 -201.7 -83.1 IId -420.5 -449.6 -97.8 As well as in the previous case, all reactions are exothermic and have large negative reaction entropy values. Most favorable, from the thermodynamic point of view, is formation of structures IId, in which the proton is coordinated by three oxygen atoms. All the above reactions proceed with decreasing free energy. The calculated dipole moment of structure IIa is 7.45D, structure IIb 5.48D, structure IIc 3.10D, structure IId 1.69D. Conclusions 1. The thermodynamic parameters of protonation reaction of ozone in the singlet and triplet electronic configuration described with the quantum-chemical method B3LYP / 6-311 ++ G (df, p). 2. Process of protonation of ozone is exothermic, occurs with decreasing of the free energy and entropy decrease. The most favorable in the reactions of the proton with singlet and triplet ozone is formation of an ion in which the proton is coordinated with all three oxygen atoms. References [1] Lunin V.I., Popovich M.N., Tkachenko S.N. Physical chemistry of ozone. M.: MSU. 1998. 481p. [2] Ngo Quyen Quy, Grigoriev E.I., Kianenko E.A., Zaynullina L.R., Petukhov А.А. The use of ozone for wastewater treatment technology in the production of styrene. Bulletin of Kazan Technological University. 2013. Vol.16. №7. P.247-249. [3] Ngo Quyen Quy, Kianenko E.A., Zaynullina L.R., Petukhov А.А., Grigoriev E.I. Changing the pH of the water during ozonation. Bulletin of Kazan Technological University. 2013. Vol.16. №10. P.232234. [4] Ngo Quyen Quy, Grigoriev E.I., Petukhov А.А. The interaction of ozone with distilled water. Bulletin of Kazan Technological University. 2014. Vol.17. №1. P.49-59. [5] Gaussian 09, Revision A.01, M.J. Frisch at all. Gaussian, Inc., Wallingford CT. 2009. [6] Shamsutdinov T.F., Chachkov D.V., Nikolaeva E.V., Shamov A.G., Khrapkovckiy G.M., Shamsutdinov T.F. Theoretical study of the mechanism of gas-phase elimination of nitrous acid from aliphatic C- and O-nitro compounds. Bulletin of Kazan Technological University. 2003. №2. P.27-33. [7] Gimadeev A.A., Chachkov D.V., Sagadeev E.V., Barabanov V.P., Gimadeev A.A. Empirical and empirical calculation of enthalpies of standard amino acids formation. Bulletin of Kazan Technological University. 2009. №3. P.7-10. [8] Kausch M., von Rague Schleyer P. Isomeric Structures of Protonated Ozone: A Theoretical Study. Journal of computational chemistry. 1980. Vol.1. №1. P.94-98.