Hydrogen fluoride structure

Silicon tetrafluoride is a colourless gas, b.p. 203 K, the molecule having, like the tetrahalides of carbon, a tetrahedral covalent structure. It reacts with water to form hydrated silica (silica gel, see p. 186) and hexafluorosilicic acid, the latter product being obtained by a reaction between the hydrogen fluoride produced and excess silicon tetrafluoride ... 

Representing a two electron covalent bond by a dash (—) the Lewis structures for hydrogen fluoride fluorine methane and carbon tetrafluoride become... 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

Similar observations led Bernstein and co-workers" to assign structure (108a) to the rearrangement product of 5a,6a-oxido-3)5,17a-dihydroxy-6j5-methylpregnan-20-one 17-acetate (106) with anhydrous hydrogen fluoride or... 

The experimental bond length for the hydrogen fluoride molecule is 0.917A. Determine the basis set required to predict this structure accurately. Perform your optimizations at the MP4 level of theory (electron correlation is known to be important for this system). 

The crystal structure of many compounds is dominated by the effect of H bonds, and numerous examples will emerge in ensuing chapters. Ice (p. 624) is perhaps the classic example, but the layer lattice structure of B(OH)3 (p. 203) and the striking difference between the a- and 6-forms of oxalic and other dicarboxylic acids is notable (Fig. 3.9). The more subtle distortions that lead to ferroelectric phenomena in KH2PO4 and other crystals have already been noted (p. 57). Hydrogen bonds between fluorine atoms result in the formation of infinite zigzag chains in crystalline hydrogen fluoride... 

Hydrogen abstraction reactions potential surfaces for, 25-26,26,41 resonance structures for, 24 Hydrogen atom, 2 Hydrogen bonds, 169,184 Hydrogen fluoride, 19-20, 20,22-23 Hydrogen molecules, 15-18 energy of, 11,16,17 Hamiltonian for, 4,15-16 induced dipoles, 75,125 lithium ion effect on, 12... 

Due to its strong hydrogen bonds, in the vapor state hydrogen fluoride is found as short chains and rings. Draw the Lewis structure of an (HF)3 chain and indicate the approximate bond angles. 

The Crystal Structure of Ammonium Hydrogen Fluoride, NH4HF2... 

Hassel and Luzanski obtained quadratic tabular crystals on evaporation of an aqueous solution containing excess hydrogen fluoride. Laue photographs with the incident beam normal to the basal plane showed rhombic symmetry, with, however, appreciable approximation to ditetragonal symmetry. The unit of structure has the dimensions... 

The Lewis structure of hydrogen fluoride shows three lone pairs on the fluorine atom. These nonbonding electrons are localized in atomic orbitals that belong solely to fluorine. Remembering that one of the fluorine 2 p orbitals is used to form the H—F bond, we conclude that the three lone pairs must occupy the remaining pair 2 p orbitals and the 2 s orbital of the fluorine atom. 

Nitric acid is indicated as being particularly dangerous with carboxylic acids. It is interesting to note that an accident is reported with the nitric acid/lactic acid mixture combined with hydrogen fluoride in actual fact, lactic acid has a structure which is very close to that of this particular compound. The latter will certainly be less reactive due to the steric nature of the second methyl group. 

Hirata and Iwata, 1998, extended these studies to linear oligomers and an infinite linear hydrogen fluoride polymer. Also this study substantiates the applicability of the BLYP and B3LYP functionals, for which reasonable agreement with experiment has been found with respect to structure, binding energies and vibrational frequencies of the species explored. 

Hirata, S., Iwata, S., 1998, Ab Initio Hartree-Fock and Density Functional Studies on the Structures and Vibrations of an Infinite Hydrogen Fluoride Polymer , J. Phys. Chem A, 102, 8426. 

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