4796-33-2Relevant academic research and scientific papers
19F and 13C NMR Study of Some Norborn-7-yl Fluoride Derivatives
Adcock, William,Angus, Donald I.,Lowe, David A.
, p. 675 - 680 (2007/10/03)
A series of norborn-7-yl fluorides were synthesized and their 19F and 13C NMR spectra were recorded. The 19F chemical shift trends and the one-bond carbon-fluorine coupling constants (1JCF) were examined and are discussed in the light of computed geometries for 7-norbornyl fluoride (4), 7-anti-norbornenyl fluoride (7), 7-syn-norbornenyl fluoride (9), 7-fluoronorbornadiene (3) and their hydrogen analogues. Most importantly, the introduction of a double bond into the norbornyl skeletal framework anti to the carbon-fluorine bond is shown clearly to induce a large downfield fluorine shift. By contrast, where the double bond is syn disposed the corresponding effect is very small. The origin of the large anti effect has been ascribed to neutral homohyperconjugation (π → σ*CF). This electron delocalization mechanism appears also to impinge significantly on the 1JCF coupling trends with significant ramifications on the proportionality between the s character of the C-F bond and the corresponding 1JCF, coupling.
