Naslov
C-F Coupling for Stereostructure Determination for Trifluoromethyl Substituted Dibenzosemibullvalenes and Dibenzobarrelene
(C-F Coupling for Stereostructure Determination for Trifluoromethyl Substituted Dibenzosemibullvalenes and Dibenzobarrelenes)

Autori
Lončar, Linda ; Mintas, Mladen ; Vikić-Topić, Dražen

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
The tenth Dubrovnik Internationac Coure and Conferece on the Interfaces among Mathematics, Cemistry and Computer Sciences

Mjesto i datum
Dubrovnik, Hrvatska, 26.06.1995. - 01.07.1995

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
supstituirani dibenzosemibulvaleni i dibenzobarelena
(c-f couplings; dibenzosemibullvalenes; dibenzobarrelenes)

Sažetak
Fluorinated compounds are very interesting from the spectroscopical point of view due to strong and long ranfe interactions of fluorine with atoms In 13NMR spectra of aromatic molecules carbon-fluorine couplin even through ten bonds, while fluorine induced chemical shifts even through fourteen bonds, have been detected. In aliphatic compounds these effects are of much shorte range, e.g. in the case of C-F coupling very rarely through more than three bonds, but they might show relation to the molecular shape. We have prepared regiospecifically trifluoromethyl substituted dibenzobarrelenes (1) and dibenzosemibullvalenes (2), which are interesting due to their rigid geometry. The longest C-F coupling constant observed was through five bonds, amounting to 2, 57 Hz in molecule (1) with Rl=H, R2=CF3, R3=Ph and R4=CF3, and l.48 Hz in (2), with R1=CF3, R3=Ph and R4=H, in both molecules at ortho carbons of substituted phenyl ring. Few four-bond couplings were also observed although of lower similar magnitude to five-bond ones. This was explained by significant through-space contribution to five-bond coupling here. Three-bond C-F couplings, ranging from l, 23 Hz to 5, 6 Hz, showed to dihedral angles. In addition, three-bond C-F couplings reflect preferent orientation of trifluoromethyl group which was confirmed by X-ray structural analysis. The assignment of C-F multiplets was corroborated by HMQC spectra as wel. In general, the magnitude and the multiplicity of C-F coupling showed to be a good stereochemical probe in compounds investigated here.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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