Effect of substituents on the 13C-NMR chemical shifts of 3-methylene-4-substituted-1, 4-pentadienes - Part I
| Autor: | Valentić Nataša V., Vitnik Željko J., Kozhushkov Sergei I., de Majere Armin, Ušćumlić Gordana S., Juranić Ivan O. |
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| Jazyk: | angličtina |
| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Journal of the Serbian Chemical Society, Vol 68, Iss 2, Pp 67-76 (2003) |
| Druh dokumentu: | article |
| ISSN: | 0352-5139 1820-7421 05660998 |
| DOI: | 10.2298/JSC0302067V |
| Popis: | The principles of linear free energy relationships were applied to the 13C substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the substituent parameters of Swain and Lupton provide a mutually consistent picture of the electronic effects in these compounds. The pattern of the electronic effects can be fully rationalized by a model based on the direct transmission of substituent effects through-space (direct through-space field effects), and via conjugative interactions (resonance effects), or by substituent-induced polarization of the ¶-system in the unsaturated chain (¶-polarization effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis conformation of 3-methylene-4-substituted-1,4-pentadienes as the one with minimal heat of formation. |
| Databáze: | Directory of Open Access Journals |
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