QUANTUM-CHEMICAL STUDY OF FURFURAL MOLECULE

ABSTRACT

Quantum chemical calculations were performed to determine the spatial and electronic structure of the furfural molecule, atomic charges, distances between atoms.

АННОТАЦИЯ

Проведены квантово-химические расчеты для определения пространственного и электронного строения молекулы фурфурола, зарядов атомов, расстояний между атомами.

Keywords: furfural, molecule, quantum chemical calculation, charge

Ключевые слова: фурфурол, молекула, квантово-химический расчет, заряд.

In modern chemistry, there are different ways to study the spatial and electronic structure of a molecule of matter, and the interatomic and intermolecular interactions. In particular, the study of the results obtained by theoretical methods in comparison with the results obtained by experimental physicochemical research methods allows to draw clear conclusions. Because the full study of the properties of substances plays an important role in practice, production and industry. Modern quantum chemical calculation methods are widely used to obtain these necessary conclusions [1]. The GAUSSIAN program is the most popular tool among chemists to perform quantum chemical calculations. The main reasons for this are the breadth, speed, high efficiency and user-friendliness of the coverage of this program.

The program is based on the basic laws of quantum mechanics, allowing us to estimate many other properties of molecules derived from properties such as energies, molecular structures, and oscillation frequencies of molecular systems. Based on the results obtained, it helps to have theoretically accurate and reliable conclusions on the extraction of other compounds of the studied substance molecule.

In this paper, quantum chemical calculations are performed using modern Gaussian software. The program calculated the charge of the atoms in the furfural molecule and the lengths of the interatomic bonds.

One of the products of the reaction between furfural and furan is a compound with the molecular formula C5H4O2. Furfural is obtained industrially by the action of acids on plant residues containing pentosan polysaccharides. Furfural is similar in properties to benzaldehyde and undergoes all of its characteristic reactions. Therefore, furfural is an important raw material in organic synthesis. Furfural has fungicidal and bactericidal properties, many of which are widely used in agriculture. Table 1 below shows the physicochemical properties of furfural [2].

Table 1.

Physicochemical properties of furfural

As is known, the physicochemical properties and reactivity of molecules are associated with their electronic structure and energy features [3]. The rapid development of quantum-chemical calculations and the advent of powerful computer tools made it possible to determine many properties of complex organic substances. In connection with therefore, in quantum-chemical and molecular-dynamic studies, when obtaining information necessary to create certain regularities and mechanisms for the synthesis of organic compounds, these methods of physicochemical research are of particular importance [4]. Quantum chemistry makes it possible to explain experimental data on the reactivity of organic compounds and to predict possible reactions. The basis of modern quantum chemistry is the Schredinger equation, which is usually for stationary states is solved in the adiabatic.

Quantum chemical calculations to find the optimized geometry of the furfural molecule were performed in the Gaussian98 program with a density function DFT / B3LYP method with a 3-21G base set . Figure 1 below shows the conditional numbering of the atoms of the fufurаl molecule and a program optimized 2D planar view, and Table 2 shows the calculation results.

1 a                                                                       1 b

Figure 1. a - conditional numbers of atoms in the furfural molecule; b is the charge distribution in the atoms in the furfural molecule optimized using the application.

Table 2.

Geometric parameters and charges of atoms of a furfural molecule

It can be seen from this table that the atoms of furfural O1, C3, C4, O7 showed negative (q ≈ -0.493; -0.185; -0.251; -0.432 e) charges, respectively. However, it should be noted that the maximum negative charges are on the O1 and O2 atoms. All other atoms showed positive charges. It was calculated that the highest charges in the positive state were in the H3 and H5 atoms (q ≈ 0.220; 0.232 e). The highest value of the bond length between the atoms was shown in the bond between the atoms of the furan ring and the aldehyde group attached to it, C2-C6 atoms (d ≈ 1,447Å). The shortest bond lengths were found to be between the carbon-hydrogen bonds in the furan ring: d_C3-H3, d_C4-H4, and d_C5-H5 respectively (d ≈ 1,076; 1,076; 1,074 Å), respectively. The observed charge distribution and bond lengths are consistent with the classical notion that the furfural is easily attacked by electrophiles on the oxygen atom in the aldehyde group [5]. The electrophilic exchange in the furan ring occurs at the α-carbon atom.

Conclusion. The Gaussian98 program determined the necessary information about the furfural molecule. The electronic structure of the furfural molecule was determined, and the distribution of electronic charges and geometric quantities in the atoms were calculated with high accuracy. Through the electronic structure of the molecule, the reactivity of individual atoms was determined.

References:

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2. Пономарев А.А. Синтезы и реакции фурановых веществ.- Издательство Саратовского университета. 1960.
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4. Парманов А.Б., Нурмонов С.Э., Беата Колесинско, Хандамов Б.Н. Синтез виниловых эфиров карбоновых кислот  с  участием  2-хлор-4,6-диметокси-1,3,5-триазина  //  Молодежь-как  движущая  сила  развития  науки. Меж. конф. Чимкент, Казахстан-2019. 3-мая. С. 183-185. 
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