Refereed journal article or data article (A1)

Enthalpies of Combustion and Formation of Severely Crowded Methyl-Substituted 1,3-dioxanes. The Magnitudes of 2,4-and 4,6-diaxial Me,Me-Interactions and the Chair-2,5-twist Energy Difference

List of Authors: Pihlaja K, Kivelä H, Vainiotalo P, Steele WV

Publisher: MDPI

Publication year: 2020

Journal: Molecules

Journal name in source: MOLECULES

Journal acronym: MOLECULES

Volume number: 25

Issue number: 12

Number of pages: 6

eISSN: 1420-3049


Self-archived copy’s web address:

Enthalpies of combustion of 2,2-trans-4,6- (1) and 4,4,6,6-tetramethyl- (2) and 2,4,4,6,6- (3) and 2,2,4,4,6-pentamethyl-1,3-dioxanes (4) were determined to estimate their enthalpies of formation in the gas phase. By comparing the latter with the corresponding enthalpies estimated based on the various bond-bond interactions allowed to determine the chair-2,5-twist energy difference (Delta H-CT= 29.8 kJ mol(-1)) for 1 since C-13 shift correlations indicate that it escapes to the 2,5-twist form where the 2-methyl groups are isoclinal and 4- and 6-methyl groups pseudoequatorial to avoid syn-axial interactions. Compounds 2 and 3 in turn give the values 21.0 and 21.6 kJ mol(-1)for the 4,6-diaxial Me,Me-interaction. Finally compound 4, which retains the chair conformation to avoid pseudoaxial interactions in the twist forms gives the value 19.5 kJ mol(-1)for the 2,4-diaxial Me,Me-interaction indicating that its chair form appears to be somewhat deformed.

Downloadable publication

This is an electronic reprint of the original article.
This reprint may differ from the original in pagination and typographic detail. Please cite the original version.

Last updated on 2022-07-04 at 18:40