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Potassium iodide
Product Manager
Sandra Forbes
Potassium iodide is an ionic compound which is made of the following ions: K+ I−. It crystallises in the sodium chloride structure. It is produced industrially by treating KOH with iodine.
It is a white salt, which is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It absorbs water less readily than sodium iodide, making it easier to work with.
Aged and impure samples are yellow because of the slow oxidation of the salt to potassium carbonate and elemental iodine.
4 KI + 2 CO2 + O2 → 2 K2CO3 + 2 I2
Inorganic chemistry
Since the iodide ion is a mild reducing agent, I− is easily oxidised to iodine (I2) by powerful oxidising agents such as chlorine:
2 KI(aq) + Cl2(aq) → 2 KCl(aq) + I2(aq)
This reaction is employed in the isolation of iodine from natural sources. Air will oxidize iodide, as evidenced by the observation of a purple extract when aged samples of KI are rinsed with dichloromethane. As formed under acidic conditions, hydriodic acid (HI) is a stronger reducing agent.
Like other iodide salts, KI forms triiodide (I3−) when combined with elemental iodine.
KI(aq) + I2(s) → KI3(aq)
Unlike I2, I3− salts can be highly water-soluble. Through this reaction, iodine is used in redox titrations. Aqueous KI3 (Lugol's iodine) solution is used as a disinfectant and as an etchant for gold surfaces.
Potassium iodide and silver nitrate are used to make silver(I) iodide, which is used for high speed photographic film and for cloud seeding:
KI(aq) + 9 AgNO3(aq) → AgI(s) + KNO3(aq)
Organic chemistry
KI serves as a source of iodide in organic synthesis. A useful application is in the preparation of aryl iodides from arenediazonium salts.
KI, acting as a source of iodide, may also act as a nucleophilic catalyst for the alkylation of alkyl chlorides, bromides, or mesylates.
Recent Literature
The combination of triflic anhydride and potassium iodide served as an efficient promoter for the deoxygenation of sulfoxides, yielding the corresponding sulfides in excellent quantities when conducted in acetonitrile at room temperature. This reagent system exhibits chemoselectivity and demonstrates tolerance towards a variety of functional groups, including alkenes, ketones, esters, aldehydes, acids, and oximes.
K. Bahrami, M. M. Khodaei, A. Karimi, Synthesis, 2008, 2543-2546.
Quoted from:
https://www.organic-chemistry.org/chemicals/reductions/potassiumiodide.shtm
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Categories: Technical articles