Benzenes, fluorinated hydrogen bonding

Benzylic carbon-hydrogen bonds in compounds such as methylpentafluoro-benzene, fluoromethylpentafluorobenzene, and difluoromethylpentafluoroben-zene are not capable of metalation by butyllithium Instead nucleophilic substitution of the para fluorines occurs m each example [55] (equation 13)... 

At 400°C and without a catalyst, chlorine reacts in its atomic form and causes a free-radical substitution. Of all the bonds to carbons of the benzene ring, the bond between carbon and nitrogen is the weakest (292 kJ, 70 kcal/mol) compared to carbon-hydrogen bond (415 kJ, 99 kcal/mol) and carbon-fluorine bond (443 kJ, 106 kcal/mol). Therefore, atomic chlorine cleaves the bond between carbon and nitrogen and replaces the nitro group. The product is l-chloro-3,4-difluorobenzene (compound Q) [36. ... 

Fluorinated benzenes, in general, have been shown to form intermolecular hydrogen bonds in the solid state. Among those fluorobenzenes, the X-ray crystal structure of 1,2,4,5-tetrafluorobenzene (24) exhibited the shortest intermolecular H F distance of... 

In quinoline and isoquinoline, the benzene ring is more receptive to fluorma-tion, its double bonds being saturated and the hydrogen atoms replaced in preference to those in the pyridine ring As with pyridine and its homologues, ring contraction takes place during fluorination with cesium tetrafluorocobaltate at... 

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