- Nuclear spin-spin coupling via nonbonded interactions. 8. The distance dependence of through-space fluorine-Fluorine coupling
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The 19F19F nuclear spin-spin coupling constants J(FF) for a set of eighteen compounds related structurally to 1,8-difluoronaphthalene were measured by 19F NMR spectroscopy. The FF distances d(FF) in these compounds were determined by ab initio 3-21G* molecular orbital calculations. Consistent with the lone-pair overlap theory of the origins of through-space 19F19F coupling, an exponential relationship is found between J(FF) and d(FF) (regression coefficient r2 = 0.991), and a linear relationship is found between J(FF) and the extent of the overlap interaction between the in- plane fluorine 2p lone-pair orbitals (regression coefficient r2 = 0.993). The magnitudes of these lone-pair interactions were estimated from molecular orbital energies obtained by ab initio 6-31G* calculations for a model consisting of a pair of HF molecules separated by various distances.
- Mallory, Frank B.,Mallory, Clelia W.,Butler, Kelly E.,Lewis, Mary Beth,Xia, Angell Qian,Luzik Jr., Eddie D.,Fredenburgh, Laura E.,Ramanjulu, Mercy M.,Van, Que N.,Francl, Michelle M.,Freed, Dana A.,Wray, Chandra C.,Hann, Christine,Nerz-Stormes, Maryellen,Carroll, Patrick J.,Chirlian, Lisa E.
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p. 4108 - 4116
(2007/10/03)
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- Synthesis and experimental study of through-space hydrogen-fluorine and carbon-fluorine spin-spin coupling in 4,5-substituted 1-acetyl-8-fluoronaphthalenes
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The synthesis and NMR study (1H, 13C, and 19F) of a complete series of 4,5-substituted 1-acetyl-8-fluoronaphthalenes are reported. This data revealed a 6J(H,F) and a 5J(C,F) through space coupling between the fluorine and the methyl on the acetyl group (1H and 13C). The magnitude of this coupling constant changes depending on the nature of the substituent at C-4, the internuclear distance, and the solvent.
- Jaime-Figueroa, Saul,Kurz, Lilia J.,Liu, Yanzhou,Cruz, Raymundo
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p. 1167 - 1178
(2007/10/03)
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- Fluorination with Xenon Difluoride. 23. Fluorination of Ortho Substituted Aromatic Molecules
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The fluorination of 9,10-dihydroxyanthracene and triptycene with xenon difluoride in the presence of hydrogen fluoride occured at α and β position with β attack predominating over α attack, while the reaction with acenaphthalene resulted in the formation of 2- and 4-fluorosubstituted products, regioselectivity being very little affected by the nature of the catalyst: hydrogen fluoride, boron trifluoride and pentafluorothiophenol.The fluorination of 1,2,3,4-tetrahydro-1,4-methanonaphthalene resulted in the formation of 6-fluoro-1,2,3,4-tetra-hydro-1,4-methanonaphthalene, 6,7-difluoro-1,2,3,4-tetrahydro-1,4-methanonaphthalene and rearranged product 1-(2,2-difluoroethyl)indan.
- Sket, Boris,Zupan, Marko
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p. 279 - 281
(2007/10/02)
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