Hydrogen fluoride pyridine

Chemical identity:
– Hydrogen Fluoride 55%-75%
– Pyridine 25%-45%
State: Liquid
Color: Colorless to brown
Solubility in water: reacts violently
Boiling point/range°C: 50/lmm
Relative density: l.lg/cm3

Pyridine HF is a form of hydrogen fluoride used in pharmaceutical manufacturing and fluorine synthesis.

Stable under recommended transport or storage conditions and normal conditions. Avoid: Heat, fire and water; strong bases, alkali metals, strong oxidizing agents, metals and strong acids. Reacts violently with water. During combustion, may emit toxic carbon dioxide / carbon fumes.

Some of the problems with HF can be minimized by combination with an amine, thereby making the reagent much less volatile and safe to use in ordinary lab glassware. Such reagents are suitable for desilylation and displacement of alkyl and aryl halides. The electron density of the fluoride anion is somewhat reduced compared to HF itself. These reagents are more effective when less electrophilic substrates are activated for nucleophilic attack. Epoxides, activated by their ring strain, convert well to 1,2-fluoroalcohols. Olefins, activated with an oxidant like NBS, convert to 1,2-fluorobromides (Markovnikov addition of fluoride). Either of these products can be converted to fluoro-olefins, which can be subsequently converted to difluorides. The same combination of reagents can convert thio ketals to geminal difluorides. Alcohols and phenols, through their intermediate xanthates, are converted to trifluoromethyl ethers. 1

1 (Org. Process Res. Dev., 2008, 12, 308 and references therein).