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

Title of the article: Расчет распределения зарядов на углеродных атомах алкоксильной части сложных эфиров одноатомных спиртов квантово-химическими методами

Year: 2024, Issue: 4, Pages: 70-78

Branch of knowledge: 2.6.10. Organic matter technology

Index UDK: 544.43:547-31

DOI: 10.26730/1999-4125-2024-4-70-78

Abstract: For methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, tert-butyl acetate, pentyl acetate, neopentyl acetate, hexyl acetate, 2-hexyl acetate, 3-hexyl acetate, as well as cyclohexyl acetate for cyclohexanol 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 on all types of alkoxy group’s carbon atoms of esters. Orbital occupation analysis was performed by natural valence orbitals (NBO) using Malliken schemes (MPA) and natural scheme (NPA). It was shown that for calculation according to the NPA scheme, a good correlation is observed for the charge changes and chemical shift on the α-carbon atom of the alkoxy group of the primary alcohol esters having normal structure with an increase in the length of the hydrocarbon skeleton in the range of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate and hexyl acetate. In the row of isopropyl acetate, sec-butyl acetate, 2-hexyl acetate, 3-hexyl acetate, cyclohexyl acetate, both the values of charges calculated according to the NPA scheme and the values of chemical shifts on the α-carbon atoms of the alkoxy group practically do not depend on the value and structure of the alcohol hydrocarbon radical, and the values of charges calculated according to the MPA scheme are reduced. As hydrogen atoms are replaced at the α-carbon atom in the series methanol, ethanol, 2-propanol, tert-butyl alcohol with methyl radicals, the value of chemical shift increases and charges calculated according to the NPA scheme. In changing of charges values calculated according to the MPA scheme, there is no obvious dependence. It was concluded that the experimental values of chemical shifts and the results of charges calculation on carbon atoms of alkoxy group of saturated monohydric alcohols obtained according to the NPA scheme are good matched.

Key words: esters alkoxy group quantum chemical calculation charges chemical shift conformation «chair» «boat»

Receiving date: 01.05.2024

Approval date: 25.07.2024

Publication date: 26.09.2024

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