Circumambulatory Rearrangements of 5-Halo-1,2,3,4,5-pentaphenylcyclopentadienes

Autor:	Igor E. Mikhailov, Vladimir I. Minkin, Galina A. Dushenko
Rok vydání:	2020
Předmět:	010405 organic chemistry Chemistry Organic Chemistry Nuclear magnetic resonance spectroscopy Ring (chemistry) 01 natural sciences Transition state 0104 chemical sciences Crystallography Intramolecular force Halogen Molecule Halo Enantiomer
Zdroj:	Russian Journal of Organic Chemistry. 56:1744-1752
ISSN:	1608-3393 1070-4280
Popis:	DFT quantum chemical calculations at the CAM-B3LYP/Def2TZVP level of theory showed that intramolecular migrations of halogens in 5-halo-1,2,3,4,5-pentaphenylcyclopentadienes (C5Ph5Hlg, Hlg = F, Cl, Br, I) involve chiral conformation of their molecules with a propeller arrangement of phenyl groups via 1,5-sigmatropic shifts around the five-membered ring through asymmetric transition states with energy barriers ΔE≠ZPE of 42.5 (F), 26.2 (Cl), 20.2 (Br), and 15.2 kcal/mol (I). The results were consistent with the data of dynamic NMR spectroscopy. The P and M enantiomers are readily interconvertible (ΔE≠ZPE = 1.7–3.7 kcal/mol) by way of synchronous flips of the phenyl groups. The calculated barriers to alternative 1,3-halogen shifts in C5Ph5Hlg are considerably higher than those for 1,5-shifts: ΔE≠ZPE = 60.7 (F), 38.6 (Cl), 32.0 (Br), and 27.9 kcal/mol (I).
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::944eed748b97ab0fa8d18d7249df983e https://doi.org/10.1134/s1070428020100127 Zobrazit plný text záznamu Plný text ve formátu PDF Plný text ve formátu HTML
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