Lithium iodide

DescriptionLithium iodide (chemical formula: LiI) is the compound of lithium and iodine. It can be used as an electrolyte in high-temperature batteries, long-life batteries which is required, e.g. by artificial pacemaker as well as in the electrolyte of dye-sensitized solar cells. In organic synthesis, it can be used for C-O bonds cleavage such as converting methyl esters to carboxylic acids. In addition, it can be used as a radio contrast agent for X-ray computed tomography imaging studies.

UsesLithium iodide can be used for the catalytic dehydrogenation of hydrocarbons. Oxidation of lithium iodide yields iodine which reacts with the hydrocarbon to form an organic iodide. The intermediate is dehydroiodinated to yield an olefin.For example, butane may be converted to butadiene.

UsesControls regioselectivity in palladium catalyzed allylic alkylation reactions.1

UsesIt is used as a absorbent in refrigeration process, as a catalyst, and in photography. It is also useful for organic synthesis, pessat iodination, cleavage of esters, ethers, epoxides, decarboethoxylation, carbonylation, and aldol condensation. It is used for manufacturing medicines and mineral waters. It is used in electochemicstry and redox reactions. Lithium iodide is also a catalyzed conjugate addition reaction of β-dicarbonyl compounds. It is also useful for tetrathioquinodimethane.

UsesControls regioselectivity in palladium-catalyzed allylic alkylation reactions.

PreparationThe laboratory preparation of lithium iodide is carried out in much the same way as the industrial preparation. Lithium iodide is prepared by the reaction of lithium hydroxide monohydrate or lithium carbonate with hydriodic acid, which may be prepared in situ by the reduction of iodine. The iodide is usually not isolated as the anhydrous material but is used as a solution or as the solid lithium iodide trihydrate. Hydriodic acid may be prepared by the reaction of hydrogen sulfide and iodine. The hydriodic acid solution must be kept under an inert atmosphere to prevent air oxidation to iodine. After combination of the acid with the lithium compounds, the solution may be evaporated to yield lithium iodide trihydrate, LiI· 3H20. The anhydrous material may be made by extremely careful dehydration of the trihydrate under vacuum and with slow heating. The lithium iodide or its trihydrate must be handled under an inert atmosphere to avoid oxidation of the iodide ion to iodine.

PreparationThe trihydrate salt is obtained by neutralization of lithium hydroxide or lithium carbonate solution with pure hydriodic acid followed by concentration of the solution for crystallization: LiOH + HI → LiI + H2O When heated in a vacuum, the trihydrate dehydrates to anhydrous salt.