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The carbon–fluorine bond of the smaller molecules is formed in three principal ways: Fluorine replaces a halogen or hydrogen, or adds across a multiple bond. The direct reaction of hydrocarbons with fluorine gas can be dangerously reactive, so the temperature may need to be lowered even to −150 °C (−240 °F). [115] "
Hydrogen and fluorine combine to yield hydrogen fluoride, in which discrete molecules form clusters by hydrogen bonding, resembling water more than hydrogen chloride. [ 126 ] [ 127 ] [ 128 ] It boils at a much higher temperature than heavier hydrogen halides and unlike them is miscible with water. [ 129 ]
The electrowinning of aluminium relies on the electrolysis of aluminium fluoride in molten cryolite. Several kilograms of HF are consumed per ton of Al produced. Other metal fluorides are produced using HF, including uranium tetrafluoride. [14] HF is the precursor to elemental fluorine, F 2, by electrolysis of a solution of HF and potassium ...
Aluminium fluoride is an important additive for the production of aluminium by electrolysis. [4] Together with cryolite, it lowers the melting point to below 1000 °C and increases the conductivity of the solution. It is into this molten salt that aluminium oxide is dissolved and then electrolyzed to give bulk Al metal. [12]
This is in part a result of the strength of the hydrogen–fluorine bond, but also of other factors such as the tendency of HF, H 2 O, and F − anions to form clusters. [19] At high concentrations, HF molecules undergo homoassociation to form polyatomic ions (such as bifluoride, HF − 2) and protons, thus greatly increasing the acidity. [20]
Hydrogen atoms in the ammonium ion form hydrogen bonds with the fluorine atoms, and in the resulting structure, N-H-F are roughly colinear. [6] [7] As a result of these hydrogen bonds, this crystal structure varies from those of other bifluoride salts, such as potassium bifluoride and rubidium bifluoride. [5]
Hypofluorous acid, chemical formula H O F, is the only known oxyacid of fluorine and the only known oxoacid in which the main atom gains electrons from oxygen to create a negative oxidation state. The oxidation state of the oxygen in this acid (and in the hypofluorite ion OF − and in its salts called hypofluorites) is 0, while its valence is 2.
The reaction of F 2 with organic compounds is, however, highly exothermic and can lead to non-selective fluorinations and C–C cleavage, as well as explosions. [6] Only a few selective radical fluorination methods have been reported. [7] [8] The use of fluorine for radical fluorination is mainly limited to perfluorination reactions. [5]