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
Enthalpies of combustion of 2,2-<i>trans</i>-4,6- (<b>1</b>) and 4,4,6,6-tetramethyl- (<b>2</b>) and 2,4,4,6,6- (<b>3</b>) and 2,2,4,4,6-pentamethyl-1,3-dioxanes (<b>4</b>) were determined to estimate their enthalpies of formation in the ga...
| প্রধান লেখক: | , , , |
|---|---|
| বিন্যাস: | প্রবন্ধ |
| ভাষা: | English |
| প্রকাশিত: |
MDPI AG
2020-06-01
|
| মালা: | Molecules |
| বিষয়গুলি: | |
| অনলাইন ব্যবহার করুন: | https://www.mdpi.com/1420-3049/25/12/2762 |
| _version_ | 1827715091042140160 |
|---|---|
| author | Kalevi Pihlaja Henri Kivelä Pirjo Vainiotalo William V. Steele |
| author_facet | Kalevi Pihlaja Henri Kivelä Pirjo Vainiotalo William V. Steele |
| author_sort | Kalevi Pihlaja |
| collection | DOAJ |
| description | Enthalpies of combustion of 2,2-<i>trans</i>-4,6- (<b>1</b>) and 4,4,6,6-tetramethyl- (<b>2</b>) and 2,4,4,6,6- (<b>3</b>) and 2,2,4,4,6-pentamethyl-1,3-dioxanes (<b>4</b>) 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 (Δ<i>H</i><sub>CT</sub> = 29.8 kJ mol<sup>–1</sup>) for <b>1</b> 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 <b>2</b> and <b>3</b> in turn give the values 21.0 and 21.6 kJ mol<sup>–1</sup> for the 4,6-diaxial Me,Me-interaction. Finally compound <b>4</b>, which retains the chair conformation to avoid pseudoaxial interactions in the twist forms gives the value 19.5 kJ mol<sup>–1</sup> for the 2,4-diaxial Me,Me-interaction indicating that its chair form appears to be somewhat deformed. |
| first_indexed | 2024-03-10T19:10:41Z |
| format | Article |
| id | doaj.art-f9b3839c801943f693d375d543c4281e |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T19:10:41Z |
| publishDate | 2020-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-f9b3839c801943f693d375d543c4281e2023-11-20T03:53:42ZengMDPI AGMolecules1420-30492020-06-012512276210.3390/molecules25122762Enthalpies 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 DifferenceKalevi Pihlaja0Henri Kivelä1Pirjo Vainiotalo2William V. Steele3Department of Chemistry, University of Turku, FI-20500 Turku, FinlandDepartment of Chemistry, University of Turku, FI-20500 Turku, FinlandDepartment of Chemistry, University of Joensuu, FI-80100 Joensuu, FinlandDepartment of Chemistry, University of Stirling, Stirling FK9 4LA, Scotland, UKEnthalpies of combustion of 2,2-<i>trans</i>-4,6- (<b>1</b>) and 4,4,6,6-tetramethyl- (<b>2</b>) and 2,4,4,6,6- (<b>3</b>) and 2,2,4,4,6-pentamethyl-1,3-dioxanes (<b>4</b>) 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 (Δ<i>H</i><sub>CT</sub> = 29.8 kJ mol<sup>–1</sup>) for <b>1</b> 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 <b>2</b> and <b>3</b> in turn give the values 21.0 and 21.6 kJ mol<sup>–1</sup> for the 4,6-diaxial Me,Me-interaction. Finally compound <b>4</b>, which retains the chair conformation to avoid pseudoaxial interactions in the twist forms gives the value 19.5 kJ mol<sup>–1</sup> for the 2,4-diaxial Me,Me-interaction indicating that its chair form appears to be somewhat deformed.https://www.mdpi.com/1420-3049/25/12/2762crowded 1,3-dioxanesenthalpies of combustionenthalpies of formationchair-2,5-twist energy differencesyn-axial Me,Me-interactions |
| spellingShingle | Kalevi Pihlaja Henri Kivelä Pirjo Vainiotalo William V. Steele 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 Molecules crowded 1,3-dioxanes enthalpies of combustion enthalpies of formation chair-2,5-twist energy difference syn-axial Me,Me-interactions |
| title | 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 |
| title_full | 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 |
| title_fullStr | 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 |
| title_full_unstemmed | 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 |
| title_short | 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 |
| title_sort | 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 |
| topic | crowded 1,3-dioxanes enthalpies of combustion enthalpies of formation chair-2,5-twist energy difference syn-axial Me,Me-interactions |
| url | https://www.mdpi.com/1420-3049/25/12/2762 |
| work_keys_str_mv | AT kalevipihlaja enthalpiesofcombustionandformationofseverelycrowdedmethylsubstituted13dioxanesthemagnitudesof24and46diaxialmemeinteractionsandthechair25twistenergydifference AT henrikivela enthalpiesofcombustionandformationofseverelycrowdedmethylsubstituted13dioxanesthemagnitudesof24and46diaxialmemeinteractionsandthechair25twistenergydifference AT pirjovainiotalo enthalpiesofcombustionandformationofseverelycrowdedmethylsubstituted13dioxanesthemagnitudesof24and46diaxialmemeinteractionsandthechair25twistenergydifference AT williamvsteele enthalpiesofcombustionandformationofseverelycrowdedmethylsubstituted13dioxanesthemagnitudesof24and46diaxialmemeinteractionsandthechair25twistenergydifference |