Journalartikel

Autorenliste: Wilming, FM; Marazzi, B; Debes, PP; Becker, J; Schreiner, PR

Jahr der Veröffentlichung: 2023

Seiten: 1024-1035

Zeitschrift: The Journal of Organic Chemistry

Bandnummer: 88

Heftnummer: 2

ISSN: 0022-3263

eISSN: 1520-6904

DOI Link: https://doi.org/10.1021/acs.joc.2c02444

Verlag: American Chemical Society

Abstract: 
We report the synthesis of 14 2,2 '-disubstituted 9,9 '-bifluorenylidenes as molecular balances for the quantification of London dispersion interactions between various dispersion energy donors. For all balances, we measured delta G(Z/E) at 333 K using 1H NMR in seven organic solvents. For various alkyl and aryl substituents, we generally observe a preference for the folded Z-isomer due to attractive London dispersion interactions. The cyclohexyl-substituted system shows the largest Z-preference in this study with delta G(Z/E) = -0.6 +/- 0.05 kcal mol(-1) in all solvents, owing to the rotational freedom of cyclohexyl groups paired with their large polarizability that maximizes London dispersion interactions. On the other hand, rigid and sterically more demanding substituents like tert-butyl unexpectedly favor the unfolded E-isomer. This is a result of the close relative position in which the functional groups are positioned in this molecular balance. This close proximity is the reason for the increase of Pauli repulsion in the Z-isomers with large rigid substituents (tert-butyl, adamantyl, and diamantyl) which leads to an equilibrium shift toward the unfolded E-form. While we were able to reproduce most of our experimental trends qualitatively using contemporary computational chemistry methods, quantitative accuracy of the employed methods still needs further improvement.

Harvard-Zitierstil: Wilming, F., Marazzi, B., Debes, P., Becker, J. and Schreiner, P. (2023) Probing the Size Limit of Dispersion Energy Donors with a Bifluorenylidene Balance: Magic Cyclohexyl, The Journal of Organic Chemistry, 88(2), pp. 1024-1035. https://doi.org/10.1021/acs.joc.2c02444

APA-Zitierstil: Wilming, F., Marazzi, B., Debes, P., Becker, J., & Schreiner, P. (2023). Probing the Size Limit of Dispersion Energy Donors with a Bifluorenylidene Balance: Magic Cyclohexyl. The Journal of Organic Chemistry. 88(2), 1024-1035. https://doi.org/10.1021/acs.joc.2c02444