Relative Signs of Three-Bond Fluorine–Carbon and Four-Bond Fluorine–Hydrogen Couplings in 2-Substituted Fluorobenzenes
✍ Scribed by Ian D. Rae; Josephine A. Weigold; Dora G. de Kowalewski; Rodolfo R. Biekofsky; Rubén H. Contreras
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 332 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
In a series of 2-X-fluorobenzenes, the relative signs between 'J(CF) and the corresponding 4J(HF) couplings were determined. In most cases like signs were found. However, for the coupling pathway involving the X group, unlike signs were found for X = CN, NCS and NO,. For other electronegative substituents, 4J(H3F) couplings were found to have too small a magnitude to permit determination of their signs with respect to 'J(C3F). No adequate correlation between the algebraic values of 'J(C3F) couplings and the electronegativity of the substituent placed at ring position 2 was found. Some speculative arguments are advanced in order to rationalize the observed trend.