Dyotrope Wasserstoffübertragung in Dihydrosesqui- und in Dihydro-syn-sesterbicyclo[2.2.2]octenen
| Autor: | Jens Wortmann, Kathrin Pohl, Dirk Frowein, Wolfram Grimme |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
chemistry.chemical_classification
Exothermic reaction Pericyclic reaction Double bond Hydrogen Organic Chemistry chemistry.chemical_element General Chemistry Photochemistry Kinetic energy chemistry.chemical_compound symbols.namesake Crystallography chemistry Intramolecular force symbols Physical and Theoretical Chemistry van der Waals force Benzene |
| Zdroj: | Liebigs Annalen. 1996:1905-1916 |
| ISSN: | 1099-0690 0947-3440 |
| DOI: | 10.1002/jlac.199619961127 |
| Popis: | Dyotropic Hydrogen Transfer in Dihydrosesqui- and in Dihydro-syn-sesterbicyclo[2.2.2]octenes The intramolecular dyotropic hydrogen transfer is studied in dihydrosesquibicyclo[2.2.2]octenes. In the parent system 4-d2 the process transfers two hydrogen atoms from the ethano to the etheno bridge; it is thermoneutral and reversible at 200°C, In 12a, b a 1,2-dihydrobenzene acts as the hydrogen donor; the reaction is highly exothermic and occurs already at room temperature. In 19-d4 the dyotropic hydrogen exchange from a 1,2-dihydrobenzene to benzene is again thermoneutral and occurs at 200°C. The kinetic parameters of these reactions, listed in Table 7, indicate a concerted pericyclic pathway. In the extended dihydro-syn-sesterbicyclo[2.2.2]octenes 6-d2 and 15a, b two hydrogen transfers occur in sequence, the central bridge serving as a relais. Here the dyotropic processes establish equilibria between structures with stacked and isolated double bonds, allowing an evaluation of the van der Waals interaction in the former. It is found that this interaction changes with the type of the stakked π-systems from repulsive in 6-d2 to slightly attractive in 16a (see Table 8). |
| Databáze: | OpenAIRE |
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