ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
In photoreactions of α,α,α-trifluorotoluene with olefins, the mode of reaction strongly depends on the charge transfer between the starting materials. Substitution of an F-atom is preferred if the electron transfer becomes exergonic, i.e. if ΔG 〈0 according to the Rehm-Weller equation. In all other systems of ΔG 〉 0, the olefins undergo cycloaddition onto the arene ring. In the transition area of ΔG ≍ 0 eV, both the electron transfer and the reaction mode can be controlled by varying the solvent polarity. For instance, 1 and 9 mainly form cycloaddition products in dioxane (ΔG = + 0.11 eV), whereas in solvents with ε 〉 3 (ΔG 〈 0), substitution is the only observed photoreaction. Moreover, in systems of endergonic electron-transfer processes, the degree and the direction of charge transfer influence both the regio- and the stereochemistry of the cycloaddition.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19860690226
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