STUDY OF CHARGE DISTRIBUTION IN THE MOLECULES OF STARTING MATERIALS AND PRODUCTS IN THE TELOMERIZATION REACTION OF ETHYLENE

Аннотация

At the current stage of development in modern organic chemistry, the synthesis of low-molecular-weight aliphatic alcohols— particularly isopropyl and isoamyl alcohols—and the in-depth investigation of their molecular structures are of great significance. The synthesis of such compounds via telomerization reactions is considered technologically efficient, environmentally safe, and economically viable. In this study, the charge distribution in the molecules of isopropyl (C3) and isoamyl (C5) alcohols synthesized through the telomerization reaction involving ethylene and methanol was calculated using the Density Functional Theory (DFT) method. Keywords: ethylene, methanol, isopropyl alcohol, isoamyl alcohol, charge distribution, telogen, monomer, acetone. The study of charge distribution serves as a key tool in understanding the electrostatic nature of a molecule, the reactivity of functional groups, the degree of chemical stability, the potential for hydrogen bond formation, and the interaction with the surrounding environment. Therefore, the results of this research not only provide a theoretical assessment of molecular properties but also enable their modeling for practical applications. Telomerization is a process similar to radical polymerization, but it involves the formation of oligomers with limited chain length, terminating in the presence of a telogen (e.g., an alcohol). This process can be represented by the following general reaction: nCH₂=CH₂ + CH₃OH → CH₃–(CH₂CH₂)ₙ–OH Here, methanol acts as the telogen, while ethylene serves as the monomer. The process occurs in three main stages: Initiation: A radical species is generated. Propagation: Ethylene molecules successively add to the radical center. Termination: The chain terminates by reacting with the telogen. When n = 2, isopropyl alcohol is formed; when n = 4, isoamyl alcohol is produced. These products differ in both their physicochemical properties and their molecular electrostatic configurations. 90 CURRENT APPROACHES AND NEW RESEARCH IN MODERN SCIENCES International scientific-online conference Determining how charges are distributed throughout the molecule is one of the most crucial steps in chemical compound modeling. Partial atomic charges help: Identify regions of electron density, Determine nucleophilic and electrophilic centers, Calculate the dipole moment and degree of polarity, Predict the possible pathways of chemical reactions. Charge distribution represents the internal electrostatic map of a molecule. This very map determines how the molecule will react, where a bond is likely to break or form, and which region will exhibit stronger interaction with other reagents. The molecular structures of isopropyl and isoamyl alcohols were optimized using Density Functional Theory (DFT) with the B3LYP/6-31G(d) functional and basis set. All calculations were performed using the Gaussian 16 software package. The results were analyzed through Mulliken, Natural Bond Orbital (NBO), and Electrostatic Surface Potential (ESP) methods. The distribution of electronic charges across atoms within the molecules plays a crucial role in determining their chemical reactivity, physicochemical properties, and the formation of intramolecular forces (such as hydrogen bonds and dipole–dipole interactions). Quantum chemical calculations based on DFT allow for the precise visualization of atomic-level charge distribution. Below, the electron charges at the atomic level were analyzed for the molecules of ethylene, methanol, acetone, isopropyl alcohol, and isoamyl alcohol. The ethylene molecule (CH₂=CH₂) consists of two carbon atoms and four hydrogen atoms. The charges are symmetrically distributed due to the molecular symmetry. The calculation results are as follows: Atom Type Charge (e) C1 sp² C –0.174 C2 sp² C –0.174 H1–H4 1s H +0.087 91 CURRENT APPROACHES AND NEW RESEARCH IN MODERN SCIENCES International scientific-online conference Figure 1. Charge Distribution on the Atoms of the Ethylene Molecule The carbon atoms carry a slight negative charge, with electron density concentrated around the π-bond (the carbon–carbon double bond). The hydrogen atoms, on the other hand, are positively charged, making the molecule relatively unreactive toward electrophilic centers. In the methanol (CH₃OH) molecule, the oxygen atom is highly electronegative, and the electron density accumulates around this atom in the form of a negative charge: Atom Type Charge (e) C sp³ C –0.035 O sp³ O –0.682 H1 O–H +0.410 H2–H4 C–H +0.102 The oxygen atom carries a significantly negative charge and acts as a hydrogen bond acceptor. The hydroxyl hydrogen is positively charged, indicating its role as a donor in hydrogen bonding. Figure 2. Charge Distribution on the Atoms of the Methanol Molecule In the acetone (CH₃–CO–CH₃) molecule, the oxygen atom of the carbonyl group possesses the highest electron density. 92 CURRENT APPROACHES AND NEW RESEARCH IN MODERN SCIENCES International scientific-online c