Authors: S.V. Puchkov, Yu.V. Nepomnyashchikh

Title of the article: Charge distribution for alcohol atoms calculated by quantum chemical methods

Year: 2023, Issue: 3, Pages: 44-51

Branch of knowledge: 2.6.10. Organic matter technology

Index UDK: 544.43:547-316

DOI: 10.26730/1999-4125-2023-3-44-51

Abstract: For saturated monoatomic alcohols of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-2-propanol, 1-pentanol, 2,2-dimethyl-1-propanol, 1-hexanol, 2-hexanol, 3-hexanol, as well as cyclohexanol in conformations, "chair" and "boat" by the method of density functional theory (DFT) with hybrid functionality B3LYP in basis 6-311 + G (d, p), effective charges were calculated for all types of carbon atoms. Orbital occupation analysis was performed by natural valence orbitals (NBO) using Malliken schemes (MPA) and natural scheme (NPA). It was shown that when calculated according to the NPA scheme, there is a good correlation in charge changes and chemical shift on the α-carbon atom with an increase in the length of the hydrocarbon skeleton in the methanol, ethanol, 1-propanol row. Also, for secondary unbranched alcohols, with an increase in the length of the hydrocarbon skeleton of substituents at a α-carbon atom in the series 2-propanol, 2-hexanol, 3-hexanol, the charge and the value of chemical shift on the α-carbon atom increase. As hydrogen atoms are replaced at a α-carbon atom in the methanol, ethanol, 2-propanol, tert-butyl alcohol row for methyl radicals, the charge and the amount of chemical shift increases. A good correlation between charge values and chemical shift is observed for the "chair" and "boat" cyclohexanol conformation. Calculations according to the MPA scheme give a noticeably greater discrepancy between the calculated values of charges on carbon atoms of the listed alcohols and experimental values of chemical shifts.

Key words: alcohols quantum chemical calculation charges chemical shift conformation "chair" "boat"

Receiving date: 25.01.2023

Approval date: 15.06.2023

Publication date: 30.06.2023

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