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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

The contribution of non-classical CHaxMIDLINE HORIZONTAL ELLIPSISOC hydrogen bonds to the anomeric effect in fluoro and oxa-methoxycyclohexanes

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Author(s):
Piscelli, Bruno A. [1] ; O'Hagan, David [2] ; Cormanich, Rodrigo A. [1]
Total Authors: 3
Affiliation:
[1] Univ Estadual Campinas, Inst Chem, Monteiro Lobato St, BR-13083862 Campinas, SP - Brazil
[2] Univ St Andrews, Sch Chem, St Andrews KY16 9ST, Fife - Scotland
Total Affiliations: 2
Document type: Journal article
Source: Physical Chemistry Chemical Physics; v. 23, n. 10, p. 5845-5851, MAR 14 2021.
Web of Science Citations: 0
Abstract

In this theory study we demonstrate the dominance of non-classical 1,3-diaxial CHaxMIDLINE HORIZONTAL ELLIPSISOC hydrogen bonds (NCHBs) dictating a `pseudo' anomeric effect in selectively fluorinated methoxycyclohexanes and also influencing the axial preference in the classical anomeric exhibitor 2-methoxytetrahydropyran, a phenomenon which is most often described as a consequence of hyperconjugation. Analogues of methoxycyclohexane where ring CH2's are replaced by CF2 can switch to an axial preference and theory methods (NBO, QTAIM, NCI) indicate the dominance of 1,3-CHaxMIDLINE HORIZONTAL ELLIPSISOMe interactions over hyperconjugation. For 2-methoxytetrahydropyran, it is revealed that the global contribution to the anomeric effect is from electrostatic interactions including NCHBs, not hyperconjugation, although hyperconjugation (n(O) -> sigma{*}(CO) or n(O) -> sigma{*}(CC)) remains the main contributor to the exo-anomeric phenomenon. When two and three ether oxygens are introduced into the ring, then both the NCHB interactions and hyperconjugative contributions become weaker, not stronger as might have been anticipated, and the equatorial anomers progressively dominate. (AU)

FAPESP's process: 18/03910-1 - Physicochemical studies of fluorinated organic compounds: experimental and theoretical approaches
Grantee:Rodrigo Antonio Cormanich
Support Opportunities: Research Grants - Young Investigators Grants
FAPESP's process: 19/03855-3 - Synthesis of fluorinated derivatives of thymol and carvacrol and study of their physico-chemical properties
Grantee:Bruno de Almeida Piscelli
Support Opportunities: Scholarships in Brazil - Scientific Initiation
FAPESP's process: 19/05028-7 - Physico-chemical studies of organofluorine compounds: experimental and theoretical approaches
Grantee:Rodrigo Antonio Cormanich
Support Opportunities: Research Grants - Visiting Researcher Grant - International