CC BY
13
UDC 544.18
V. A Babkin, А. V. Ignatov, D. S. Andreev, A. V. Chulkova, K. Yu. Prochukhan, G. E. Zaikov
ISOMERS OF PENTENE:
THEORETICAL ESTIMATION OF ACID STRENGTH
Keywords: quantum chemical calculation, MNDO method, pentene-1, cis-pentene-2, trans-pentene-2, 2-methylbutene-1, 3-
methylbutene-1, 2-methylbutene-2, acid strength.
This article presents the quantum-chemical calculations of the pentene isomers - pentene-1, cis-pentene-2, trans-pentene-2, 2-methylbutene-1, 3-methylbutene-1 and 2-methylbutene-2 performed by the MNDO method with the optimization of geometry in all parameters by the standard gradient method. Optimized geometric and electronic structure of these compounds has been obtained. It has been established that all researched molecules ofpentenes have equal acid strength (pKa = 35-36) and relate to the class of very weak acids (pKa>14).
Ключевые слова: квантово-химический расчет, метод MNDO, пентен-1, цис-пентен-2, транс-пентен-2, 2-метилбутен-1, 3-
метилбутен-1, 2-метилбутен-2, кислотная сила.
В статье представлены квантово-химические расчеты изомеров пентена - пентена-1, цис-пентена-2, транс-пентена-2, 2-метилбутена-1, 3-метилбутена-1 и 2-метилбутена-2, выполненные методом MNDO с оптимизацией геометрии по всем параметрам стандартным градиентным методом. Получена оптимизированная геометрическая и электронная структура этих соединений. Установлено, что все исследованные молекулы пентенов обладают равной кислотной силой (рКа = 35-36) и относятся к классу очень слабых кислот (рКа> 14).
Introduction
It is known [1] that pentane consists of all 6 isomers, including cis - and trans-isomers:
1. penten-1 (a-Amylin) CH2=CH-CH2-CH2-CH3
2. Cis-penten-2 (CIS-p-Amylin) CH3-CH=CH-CH2-CH3
3. Trans-penten-2 (TRANS-P-Amylin) CH3-CH=CH-CH2-CH3
4. 2-methylbutan-1 (y-isoamylene) CH2=C(CH3)-CH2-CH3
5. 3-methylbutan-1 (a-isoamylene) CH2=CH-CH(CH3)-CH3
6. 2-methylbutan-2 (P-isoamylene) CH3-CH=C(CH3)-CH3
1-penten, for example, is most often formed as a byproduct of catalytic or thermal cracking of hydrocarbons or as a by-product of ethylene or propylene by thermal cracking of hydrocarbon fractions. 1-penten extremely stable in the form of a component mixture. Therefore, it is mixed with other hydrocarbons by alkylation with isobutane and used to produce gasoline. The process of obtaining 1-pentene, alkene with the double bond at the end of the linear chain involves the extraction from crude oil using the method of Fischer-Tropsch synthesis [1].
Pentens are identified of IR spectra and their derivatives: 1-penten and 2-penten form 3,5-(NO2)2C6H3COOAg and I2 dinitrobenzoate, melting point 76,2-77, of 124.5-125,30 °C respectively, 2-methyl-2-butene with NOCl gives nitrosochlorides, melting point 74-75 °C. Technical penten (mixture of all isomers with adding of isopentane) are used for the synthesis of maleic acid and butadiene; polymers of pentanol - lubricating oil, components of printing inks; 1-penten and 2-penten -source raw material for obtaining andhexyl amyl alcohols, and aldehydes; 3-methyl-1-butene is an intermediate in organic synthesis, are used to increase the octane number of fuels, in the
production of plastics; 2-methyl-2-butene and 2-methyl-
1-butene is used in the synthesis of isoprene, tert-amyl alcohol, andhexyl alcohols, esters [2-3].
However, despite the fact that pentene is well learned with the experimental physico-chemical methods, to date, the systematization of data on the quantum chemical calculations above isomers of electronic pentene on the nanoscale is not performed.
In this regard, the aim of this work is to present the data of quantum-chemical calculations of the molecules of all six isomers of pentene - penten-1, cis-penten-2, trans-penten-2, 2-methylbutan-1, 3-methylbutan-1 and
2-methylbutan-2, performed by the MNDO method with geometry optimization of all parameters by standard gradient method built into PC GAMES S [4], in the approximation of isolated molecules in the gas phase and theoretical evaluation of their acid strength according to the method, used repeatedly in works [910]. For a visual representation of the model molecules we used the program MacMolPlt [5].
The Results of Calculations
The total energy (E0, kJ/mol), electronic energy (Eel, kJ/mol), the maximum charge on hydrogen atom (qmaxH+), a universal indicator of acidity (pKa) of isomers of pentane are shown in table 1, which shows that they have the same acid strength (pKa = 35-36) [6-8].
Thus, we first presented a systematic data of quantum-chemical calculations of the molecules of the isomers of pentene - penten-1, cis-penten-2, trans-penten-2, 2-methylbutan-1, 3-methylbutan-1 and 2-methylbutan-2, executed by the MNDO method. Their acid strength was theoretically evaluated as pKa = 3536. It is established that the studied isomers of pentanol have the same acid strength and belong to the class of very weak H-acids (pKa>14).
Table 1 - Total energy (E0 , kJ/mol), electronic energy (Eei , kJ/mol), maximal charge on the hydrogen atom (qmaxH+), universal index of acidity (pKa) of the monomeres
№ Pentene Eo, kJ/mol Eel kJ/mol a H+ 4max рКа
1 pentene-1 [6] -75621 -292388 +0,05 35
2 cis-pentene-2 [6] -75395 -292449 +0,05 35
3 trans-pentene-2 [7] -75398 -294512 +0,05 35
4 2-methyl butene-1 [7] -75268 -298304 +0,04 36
5 3-methyl butene -1 [8] -76150 -299348 +0,05 35
6 2- methyl butene -2 [8] -75284 -297067 +0,05 35
References
1. https://ru.wikipedia.org/wiki/neHTeHbi
2. http://www.xumuk.ru/encyklopedia/2/3230.html
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4. M.W. Shmidt, K.K. Baldrosge, J.A. Elbert, M.S. Gordon, and anothers General Atomic and Molecular Electronic Structure Systems. J. Comput. Chem. №14. P. 1347-1363, 1993
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6. V.A. Babkin, A.V. Ignatov, D.S. Andreev, Yu.A. Prochukhan, K.Yu. Prochukhan, O.V. Stoyanov, G.E. Zaikov. Penten-1 and cis-pentene-2. Theoretical estimation of the acid force. "Vestnik" of Kazan Technological University. 2015, Vol. 18, №13, pp. 12-14.
7. V.A. Babkin, A.V. Ignatov, D.S. Andreev, O.V. Savchenko, K.Yu. Prochukhan, G.E. Zaikov. Isomers of trans-pentene-2 and 2-methylbutene-1. Theoretical estimation of the acid force. "Vestnik" of Kazan Technological University. 2015, Vol. 18, №14, pp. 27-29.
8. V.A. Babkin, A.V. Ignatov, D.S. Andreev, V.T. Fomichev, K.Yu. Prochukhan, G.E. Zaikov. Isomers of 3-Metylbutene-1 and 2-metylbutene-2.Theoretical Estimation of Acid Strength. "Vestnik" of Kazan Technological University. 2015, Vol. 18, №15, pp. 21-23.
9. Babkin V.A., Andreyev D.S., Zaikov G.Ye., Yarullin A.F. Kvantovo - khimicheskiy raschot nekotorykh molekul zhidkikh kristallov metodom MNDO i pervonachal'no. g.Kazan'. Vestnik Kazanskogo tekhnologicheskogo universiteta.2012g. , №8 , s . 103-114
10. V.A.Babkin, D.S.Andreyev, YU.A.Sangalov, Ye.S.Titova, S.S.Potapov. Kvantovo - khimicheskiy raschet izoolefinov i diyenov. Monografiya. g.Volgograd , Izd - vo VolGU , 2011g. 78 s.
© V. A. Babkin - Doctor of Chemistry, Full Professor, Head of Research Division, Sebryakovsky Branch of Volgograd State University of Architecture and Construction, Volvograd Region, Mikhailovka, Russia, Babkin_v.a@mail.ru, A. V. Ignatov - Bachelor of Engineering, Sebryakovsky Branch of Volgograd State University of Architecture and Construction, Volvograd Region, Mikhailovka, Russia, ignatovwork@yahoo.com, D. S. Andreev - Ph.D. Student, Sebryakovsky Branch of Volgograd State University of Architecture and Construction, Volvograd Region, Mikhailovka, Russia, power_words@mail.ru, A. V. Chulkova - Ph.D., Associate Professor, Head of Humanities Department, Sebryakovsky Branch of Volgograd State University of Architecture and Construction, Volvograd Region, Mikhailovka, Russia, 670218@rambler.ru, K. Yu. Prochukhan — Ph.D., Associate Professor of High-Molecular Compounds and Chemical Engineering Department, Bashkir State University, dissovet2@rambler.ru, G. E. Zaikov -Doctor of Chemistry, Full Professor of Plastics Technologies Department, Kazan National Research Technological University, Kazan, Russia.
© В. А. Бабкин - доктор химических наук, профессор, начальник отдела по научной работе, Себряковский филиал Волгоградского государственного архитектурно-строительного университета, Волгоградская область, Михайловка, Россия, Babkin_v.a@mail.ru, А. В. Игнатов - бакалавр, Себряковский филиал Волгоградского государственного архитектурно-строительного университета, Волгоградская область, Михайловка, Россия, ignatovwork@yahoo.com, Д. С. Андреев -аспирант, Себряковский филиал Волгоградского государственного архитектурно-строительного университета, Волгоградская область, Михайловка, Россия, А. В. Чулкова - кандидат педагогических наук, доцент, заведующий кафедры Гуманитарных и социально-экономических дисциплин, Себряковский филиал Волгоградского государственного архитектурно-строительного университета, Волгоградская область, Михайловка, Россия, 670218@rambler.ru, К. Ю. Прочухан - кандидат химических наук, доцент кафедры Высокомолекулярных соединений и химической технологии, Башкирский государственный университет, Уфа, Россия, dissovet2@rambler.ru, Г. Е. Заиков - доктор химических наук, профессор кафедры Технологии пластических масс, Казанский национальный исследовательский технологический университет, Казань, Россия.
