CC BY
24
УДК 547.512:544.183.26
V. A. Babkin, D. S. Andreev, O. V. Savchenko, V. T. Fomichev, I. Y. Velikodniy, K. Yu. Prochuhan, A. A. Krutilin, G. E. Zaikov
COMPUTER QUANTUM-CHEMICAL MODELING OF THE MECHANISM OF PROTONATION
OF O-METHYLSTEROL METHOD MNDO
Keywords: mechanism protonizataion, method MNDO, o-methylstyrenee.
For the first time it is researched of classical quantum chemical method MNDO of modeling mechanism protonizataion of o-methylstyrenee - monomer of cationic polymerization. Reaction exothermic and carry without a barrier character. Prize energy in result of reaction - 548 kDg/mol.
Ключевые слова: механизм протонирования, метод MNDO, о-метилстирол.
Впервые исследован механизм протонирования о-метилстирола классическим квантово-химическим методом MNDO. Реакция экзотермична и имеет безбарьерный характер. Тепловой эффект реакции равен 548 кДж/моль.
Introduction
For the first time experimental data for the cationic polymerization of o-methylstyrene in the presence of H2SO4, AlBr3, BF3OEt2 in metilenhloride ethyl chloride and at temperatures from -10 to -126 C0 was presented in [1]. The results of other studies on the polymerization of the monomer up to the present time almost nonexistent. In this regard, still do not know the mechanisms of elementary acts (initiation, growth, breakage), nature of active sites are not clear issues the activity and selectivity of the catalysts and the role of solvent. Study of the mechanism of protonation of o-methylsterol is the first step in exploring the enormous complex of the above tasks. In this regard, the aim of the present work a quantum-chemical study of the mechanism of protonation of o-methylsterol classical semi-empirical method MNDO .
Methodological part
To study the mechanism of protonation has been selected classical quantum-chemical method MNDO-optimized geometry for all parameters, gradient descent method, built-in Firefly [2], which is partly based on the source code GAMESS (US) [3], due to the fact that this method specifically parameterized for the best audio energy characteristics of molecular systems [4]. The calculations were performed in the approximation of isolated molecules in the gas phase in the framework of the molecular model. The mechanism of protonation of o-methylsterol was performed by the method is described in detail in [5]. As a reaction coordinate was selected distances from the proton Hi to C2 (RHiC2) and from Hi to C3 (RHiC3). Original values RH1C2 and RH1C3 was taken to be equal to 0.31 nm.
Results of calculation
The original model of the attack of the proton of the molecule o-methylsterol (coordinate values (RHiC2) and (RHiC3) varied in increments of 0.01 nm) is shown in Fig.1. The final structure formed carbocation after the attack of the proton H1 of the a -carbon atom of o-methylsterol (C2) and breaking the double bond of o-methylsterol shown in Fig. 2. The final structure formed carbocation after the attack of the H1 proton of p -carbon atom of o-methylsterol (C3) and breaking the
double bond C2 = C3 shown in Fig. 3. The change of the charges on the atoms directly involved in the protonation reaction along the reaction path joining H proton
9
R = 3.1 A *■ R = 3.1 A
У V
Fig. 1 - Source model attack the proton of the molecule o-methylsterol (coordinate values (Rmra) and (Rmra) varied in increments of 0.01 nm) [6]
to the a -carbon atom of o-methylsterol shown in Fig.6.The behavior of the total energy of the studied molecular system along the reaction path joining H1 proton to the p-carbon atom of o-methylsterol shown in Fig. 7. Alloprining charges on the atoms directly involved in the interaction of a proton and metilstirol along the path reaction Proton H1 to the p-carbon atom-metilstirol shown in Fig. 8. total energy Behaviour protonation of-metilstirol shown in Fig. 5, which confirms that all the way the movement of protons (the initiating particle) H+s along the reaction coordinates RH1C2 and RH1C3 negative values for the total energy of the system H + ... C9H10 (E0) is increasing steadily until the formation of the carbocationand is barrier-free nature as if a-and p-carbon atoms of o-metilstirola. However, the ultimate structure of the a-Proton attacks the carbon atom at 79 kJ/mol of energy cheaper than the ultimate structure of the Proton attack p-carbon atom. Win energy in a reaction attack a-carbon atom is 548 kJ/mol, and if p-carbon atom is 469 kJ/mol.
In addition, analysis of the results of quantum chemical calculations and the changing lengths of linkages
and Valence angles along the reaction coordinates in both cases, the proton attack on a-and p-carbon atoms of o-metilstirol indicates that the mechanism of the cati-onic polymerization of protonation of cationic polymer-izationgoes to the classical scheme joining proton to double bond monomer.
Thus, we first studied the mechanism of protonation-methylstyrene quantum chemical method MNDO. It is shown that this mechanism is a conventional proton addition reaction to the double bond of the olefin. The reaction is exothermic and is barrier-free character.
R= 1.49 A
Hlë
Fig. 2 - The final structure of the carbocation formed after Hi a - carbon atom of o-methylstyrene (C2)
R= 1.48 A
НП4
Fig. 3 - The final structure of the carbocation formed after proton attack Hi p - carbon atom of o-methylstyrene (C3)
Eo, wojib
12 4686
1,1
Fig. 4 - The potential energy surface of proton interactions with o-methylstyrene
ÛE, кДж/моль
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Номер ступени
Fig. 5 - Change in the total energy along the path of the proton addition reaction H1 to the carbon atom of the a-methylstyrene
ûq Номер ступени 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
0 2
0 - -о- I-0- -о- -JJ-
■а- —о -о
-о —0- ■ О- -> -О
-Н{1) -о-са{2) —□—Ср(3)
Fig. 6 - Changes in charges by some atoms along the path of the proton addition reaction H1 to the carbon atom of the a-methylstyrene
ÛE, к 0 Дк/ мол ь
-50
250
350
N
ч
С ч
123456789 10 11 12 13 14 15 16 17 18 19 20 21 Номер ступени
Fig. 7 - Change in the total energy along the path of the proton addition reaction H1 to the p-carbon atom of a-methylstyrene
ûq Номер ступени 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
. <У
03 Xf
02 -о"
- с* jy \
0 - -о-
-0,1 -
0,3
-Н(1) —0—са<2) —с^Ср(З)
Fig. 8 - Changes in charges by some atoms along the path of the proton addition reaction Hi to the p-carbon atom of a-methylstyrene
Bibliography
1. Kennedi, George. The cationic polymerization of olefins / J. Kennedy. - M., 1978. - 431 p.
2. Alex A. Granovsky, Firefly version 8, wwwhttp://classic.chem.msu.su/gran/firefly/index.html
3. Shmidt, M.W. J. Comput. Chem. / M. W. Shmidt, M. S. Gordon [and another]. - 1993. - 14. - P. 1347-1363.
methyl-1 in the presence of aluminum chloride aqua complex. "Bulletin" Kazan Technological University. 2015., T.18, №1, s.28-31.
4. Tsirelson VG Quantum Chemistry. Molecules molecular systems and solids.Publishing house "Bean", Moscow, 2010, 496 p.
6. Bode, B. M. J. Mol. Graphics Mod / B. M. Bode, M. S. Gordon. - 1998 -6. - P.133-138.
5. D S Andreev, VA Babkin, Zaikov GE Quantum-chemical study of the mechanism of initiation of an isoolefin 2-
© V. A. Babkin - Doctor of Chemical Sciences, professor, academician of Russian Academy of Natural History, academician of international academy "Contenant", E-mail: [email protected]; D. S. Andreev - graduate student of Volgograd State Technical University. E-mail: [email protected]; O. V. Savchenko - Candidate of Physico-mathematical Sciences, professor of department "Mathematical and Natural Sciences" of Volgograd State Technical University, Sebryakov's Branch. E-mail: [email protected]; V. T. Fomichev — Doctor of Engineering Sciences, professor of department "Applied Chemistry" of Volgograd State Architecture Building University. E-Mail: [email protected]; I. Y. Velikodniy - Magistrant of Engineering of Volgograd State Technical University, Sebryakovsky Branch; K. Yu. Prochukhan — Candidate of Chemical Sciences, professor of HMC department of Bashkir State University, e-mail: [email protected]; A. A. Krutilin — Candidate of Engineering Sciences, professor of department "Construction materials and building technologies" of Volgograd State Technical University, Sebryakov's Branch. E-mail: [email protected]; G. E. Zaikov - Doctor of Chemical Sciences, professor, academician of international academyof Science (Munich, Germany), Honored scientist of Russian Federation. Institute of Biochemical Physics, Moscow. E-mail: [email protected].
© В. А. Бабкин - д.х.н., профессор, академик РАЕ. Себряковский филиал Волгоградского государственного технического университета, [email protected]; Д. С. Андреев - преподаватель Волгоградского государственного технического университета, [email protected], О. В. Савченко - к. ф.- м. н, доцент, кафедра «Математических и естественно - научных дисциплин» Себряковский филиал Волгоградского государственного технического университета. [email protected]; В. Т. Фоми-чев - д.т.н., профессор, зав. каф. «Прикладной и общей химии» ИА и С ВолгГТУ; И. Ю. Великодный - магистрант, группа МС-21д Себряковский филиал Волгоградского государственного технического университета; К. Ю. Прочухан - к.х.н., доцент, кафедра «Высокомолекулярных соединений» Башкирский государственный университет. [email protected]; А. А. Крутилин - к.т.н., доцент каф. ОТД Себряковский филиал Волгоградского государственного технического университета [email protected]; Г. Е. Заиков - д.х.н., профессор каф ТПМ КНИТУ, академик международной академии творчества (Москва-Сан - Диего Россия-США). [email protected].
