Fluorine displacement, facile

With certain exceptions, primary fluorination of carbohydrate derivatives is very facile. Fluoride displacement of sulfonyloxy groups by potassium, or cesium, fluoride in 1,2-ethanediol and a variety of other solvents has frequently been used. Tetrabutylammonium (sometimes tetraethylammonium) fluoride in dipolar, aprotic solvents (mainly ace-... 

Alkoxylation in the benzene ring of quinazolines and quinazolinones is readily achieved in the presence of an ortho-nitro group, and even in the absence of a nitro group, displacement of fluorine is still quite facile. Examples of haloquinazolines to have been alkoxylated include 5-chloro-8-nitro-4(3//)-quinazolinone 187 <2005BMC5613>, 7-chloro-6-nitro-4(377)-quinazolinone 188 <1996JME267>, 4-arylamino-7-fluoro-6-nitroquinazolines 189... 

Diazotization in the presence of boron trifluoride enables diazonium tetrafluoroborates to be isolated from the reaction mixture and purified. Subsequent controlled decomposition produces the required fluoroaromatic. Although explosion hazards and the toxicity of the isolated salts are significant concerns with this process, known as the Balz-Schiemann process, 4,4 -di-fluorobenzophenone (BDF. 6) has been prepared by this route as a monomer for the production of the engineering plastic poly(ether ether ketone) , or PEEK , by condensation with 1,4-dihydroxybenzene in the presence of potassium carbonate. BDF 6 is superior to its chlorine analog because in aromatic systems the nucleophilic displacement of fluorine is more facile than that of chlorine, leading to a shorter polymerization time and a better quality product containing less degradation impurities. 

Fluoro4-nitropyridine-l-oxide undergoes facile displacement of the halogen under mild conditions. Alkoxides in general lead to replacement of fluorine at room temperature, and of both substituents at higher temperatures. ... 

A close analogue of the hydrocarbons are the fluorocarbons. The fluorine atoms are able to induce quadrupolar interactions leading to an isoenergetic double potential minimum displaced approximately 10° from the equatorial configuration. These minima are of considerable significance as they force the molecule to adopt a helical conformation and this structure is retained in the solid phase. Ultrasonic measurements combined with NMR studies of short chain fluorinated hydrocarbons confirm these theoretical predictions and indicate that facile exchange between trans minimum energy states occurs. 

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