Liquid hydrogen fluoride electrolysis

An industrial method for manufacturing fluorine gas is the electrolysis of liquid hydrogen fluoride. 

Fluorine. The distinguished chemist Henri Moissan first prepared fluorine by the electrolysis of a solution of potassium fluoride in liquid hydrogen fluoride. Because of the extreme chemical activity of this element, the electrolytic cell employed had to be made of platinum. At the present time, fluorine is produced in the laboratory and commercially by the electrolysis of fused potassium hydrogen fluoride (KHF2) in the manner described in the section on electrolysis. 

Electrochemical fluorination 168,169> is a commercial process for perfluorina-tion of aliphatic compounds. The reaction is performed in liquid hydrogen fluoride -potassium fluoride at a nickel anode. The mechanism is not known free fluorine cannot be detected during electrolysis, so it seems probable that fluorination is a direct electrochemical reaction. Theoretically, hydrogen fluoride-potassium fluoride should be a very oxidation-resistant SSE, and it might well be that the mechanism is analogous to that proposed for anodic acetamidation of aliphatic compounds in acetonitrile-tetrabutylammonium hexafluorophosphate 44 K... 

This technique is useful for monomers which are difficult to polymerize by other techniques. Thus, chlorotrifluoroethylene can be polymerized anodically with good efficiency by electrolysis in liquid hydrogen fluoride - potassium fluoride or trifluoroacetic acid - trifluoroacetic anhydride - potassium trifluoroacetate 631 ... 

Platinum is attacked only slowly by fluorine. Copper and steel can be used as containers lor the gas they are attacked by it, but become coated with a thin layer of copper fluoride or iron fluoride which then protects them against further attack. Fluorine was first made in 1886 by the French chemist Henri Moissan (1852-1907), by the electrolysis of a solution of potassium fluoride, KF, m liquid hydrogen fluoride, HF. In recent years methods for its commercial production and transport (in steel tanks) have been developed, and it is now used in chemical industry in moderate quantities. 

The original method of preparing fluorine was the electrolysis of a solution of potassium fluoride, KF, in liquid hydrogen fluoride, HF, using as the material of the containing vessel an alloy of platinum and iridium. It has since been learned that copper can be used for. this purpose. The copper is attacked by the fluorine, forming, however, a surface layer of copper fluoride which protects the tube from further corrosion. 

Electrochemical fluorination manufacture of perfluoro- compounds with functional groups by electrolysis of the corresponding nonfluorinated compounds in liquid hydrogen fluoride... 

Fluorine (F2) is obtained by the electrolysis of liquid hydrogen fluoride (HF) containing potassium fluoride (KF). (a) Write the half-cell reactions and the overall reaction for the process, (b) What is the purpose of KF (c) Calculate the volume of F2 (in liters) eollected at 24.0°C and 1.2 atm after electrolyzing the solution for 15 h at a current of 502 A. 

If F2 were formed by the electrolysis of an aqueous fluoride solution, it would immediately oxidize water to oxygen. For this reason, fluorine is prepared by electrolyzing liquid hydrogen fluoride containing potassium fluoride to increase its conductivity, at about 70°C (Figure 21.17) ... 

Numerous perfluoroalkane sulfonyl fluorides, R/S02F, are prepared by the electrolysis of sulfonyl chlorides in liquid hydrogen fluoride. From these, the corresponding perfluoroalkanesulfonic acids are obtained by (1) reaction of the sulfonyl fluoride with a base to give a salt, (2) distillation of the acid from a mixture of the salt with concentrated sulfuric acid (29, 36,115). 

Electrolysis of Liquid Hydrogen Fluoride Containing an Organic Starting Material... 

Electrochemical methods of fluorination (electrofluorination) involve the electrolysis of a liquid hydrogen fluoride solution or a molten alkali metal fluoride-hydrogen fluoride mixture containing the appropriate nitrogen compounds. The electrolysis is usually carried out at a voltage of 5 to 7 V (which is too low to liberate elemental fluorine) and at temperatures between -15 to -h20°C for the HF solution or above 100°C for the fused salt. The elimination of NF3 at the anode is always accompanied by the formation of other products, the amount of which is dependent on the conditions of the electrolysis. Table 1 lists a number of substances that give NF3 in good yields and, therefore, were proposed for preparation of NF3 in the laboratory. 

Fluorine ip2) is obtained by the electrolysis of liquid hydrogen fluoride (HF) containing potassium fluoride (KF). (a) Write the half-cell reactions and the overall reaction for the process. 

The isolation of saturated and unsaturated acetic acid derivatives in the manganese(m) acetate oxidation of olefins has been reported earlier examples of this oxidation led solely to y-lactones. A one-step synthesis of aeo-di-carboxylic acid diesters has been reported, based on Kolbe electrolysis of oxalic and malonic half-esters in the presence of olefins, and is exemplified in Scheme 2. As part of a study of insect hormone activity, Kolbe electrolysis has been utilized in the preparation of aj9-unsaturated Cj4—Cj7 acid esters with a terminal quaternary alkyl group. The utility of liquid hydrogen fluoride in the Koch carbonylation of olefins has been descried, as has a general study of this reaction. ... 

It is a toxic colourless gas which is dangerously explosive in the gaseous, liquid and solid states [1]. It is produced dining electrolysis of nitrogenous compounds in hydrogen fluoride [2], Later work (perhaps with purer material ) did not show the explosive instability [3], The shock-sensitivity is confirmed [4],... 

All methods that have been used successfully for producing fluorine in quantity are electrochemical and make use of the system hydrogen fluoride-potassium fluoride in different forms of cells and at various temperatures. Cady1 has shown by a study of the freezing points and vapor pressures of this system that there are three regions where electrolysis to produce fluorine is practicable. In each of these regions, the system is liquid, and the vapor pressure of hydrogen fluoride is below atmospheric pressure. 

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