Water hydrogen fluoride

Hydrogen bonding aeeounts for the abnormally high boiling points of, e.g., water, hydrogen fluoride, ammonia, and many organie eompounds (see later) sueh as aleohols. 

Fluoroaromatics are now produced m 75-90% yields on an industrial scale by this method The nonorganic layer containing water, hydrogen fluoride, and sodium bifluoride is treated with sulfur trioxide, and anhydrous hydrogen fluoride is recycled by distillation [54 (equation 13)... 

Using the relationship from the preceding section that the effective electronegativity of carbon in a C—H bond increases with its s character (sp < sp < sp), the order of hydrocarbon acidity behaves much like the preceding methane, ammonia, water, hydrogen fluoride series. 

Like water, hydrogen fluoride, HF, and ammonia, NH3, have relatively high boiling points. Explain. 

Fig. 10. Infrared spectrum of a water-hydrogen fluoride mixture in the region of the HF stretching vibration. The straight lines indicate the first six hot band origins. From R. K. Thomas, Proc. Roy. Soc. London A344, 579 (1975). Reproduced by permission from the Royal Society...

In an earlier paper Bevan, Legon, Millen and Rogers 84) presented the microwave spectrum of the water-hydrogen fluoride complex. For the O... F distance they obtain d 2.68 0.01 A and for the dipole moment component along the symmetry axis 3.82 0.02 D. For v they gave, as a preliminary value, 198 cm-1 and for the out-of-plane and in-plane bridge vibrations 94 and 180cm-1, respectively. A full paper has been announced. 

At substantially higher temperatures (300°C-400°C), pyrolysis of satin in the air leads almost exclusively to propylene and methyl phosphonofluoiidic acid. Over platinized alumina, there are formed stoichiometric amounts of phosphoric acid, water, hydrogen fluoride, and carbon dioxide (Baier and Weller, 1967). 

A classification scheme for molecular polarity can be based on the electric potential surrounding the molecule. Traditionally, schemes for ranking molecular polarity are based on electronegativity differences, on molecular dipole moments, or on solubility. The root-mean-square (rms) value of the molecular electric potential can be used for this purpose. Table 1 shows a ranking of 24 small molecules according to their rms electric potential. Note that all of the amides are extremely polar by this criterion, more polar than formaldehyde or water. Hydrogen fluoride is less polar than acetone, acetaldehyde, water, or the amides. At the low end of the polarity scale, the amines are surprisingly nonpolar. As expected acetylene is more polar than ethylene, which is more polar than methane. 

Water - hydrogen fluoride (1/1) (weakly bound complex)... 

Salanne M, Simon C, Madden PA (2011) Optical basicity scales in protic solvents water, hydrogen fluoride, ammonia and their mixtures. Phys Chem Chem Phys 13 6305-6308... 

Ab Initio Calculations on Hydrogen Fluoride Dimer and the Mixed Water-Hydrogen Fluoride Dimer. 

Methane Ammonia Water Hydrogen Fluoride Neon... 

Water. Hydrogen fluoride, HF, a colorless, intensely corrosive gas, even for glass, is readily soluble in water to form a weak acid (distinction from the other hydrogen halides), ionized in 1-dM solution to about 10 %. A constant boiling mixture at 112 °C is about 22 M, but the more common concentrated aqueous solution ( 49 % HF) is about 29 M. Both the solution and its vapor act on the flesh with veiy little warning to produce bums that are painful and slow to heal. Unlike the other hydrogen halides, HF is not a reducing acid. 

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