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Ammonium iodide is the inorganic compound with the formula NH 4 I. A white solid. It is an ionic compound, although impure samples appear yellow. This salt consists of ammonium cation and an iodide anion. [1] It can be prepared by the action of hydroiodic acid on ammonia. It is easily soluble in water, from which it crystallizes in cubes.
The iodide is regenerated, meaning the reaction runs with the iodide/hypoiodite as a catalyst in the presence of excess of the original strong oxidizing agent. Ammonium hypoiodites are capable of oxidizing benzylic methyl groups, [2] initiating oxidative dearomatization, [3] and oxidative decarboxylation of β-ketolactones. [4]
The enthalpy of formation Δ f H 0 of tetra-n-butylammonium iodide is −499 kJ/mol, which is lower than that for the bromide or chloride (−540, −564 kJ/mol). [2] At lower temperatures with water tetra-n-butylammonium iodide forms a clathrate hydrate. [2] The tetra-n-butylammonium cation is large and hydrophobic.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
This clock reaction uses sodium, potassium or ammonium persulfate to oxidize iodide ions to iodine. Sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color. Iodine is generated: 2 I − + S 2 O 2− 8 → I 2 + 2 SO 2− 4. And is then removed:
Ammonium bicarbonate – [NH 4]HCO 3 [35] Ammonium bisulfate – [NH 4]HSO 4 [36] Ammonium bromide – NH 4 Br [37] Ammonium chromate – [NH 4] 2 CrO 4 [38] Ammonium cerium(IV) nitrate – [NH 4] 2 [Ce(NO 3) 6] Ammonium cerium(IV) sulfate – [NH 4] 4 [Ce(SO 4) 4] Ammonium chloride – [NH 4]Cl [39] Ammonium chlorate – [NH 4]ClO 3 [40 ...
The following exergonic equilibrium gives rise to the triiodide ion: . I 2 + I − ⇌ I − 3. In this reaction, iodide is viewed as a Lewis base, and the iodine is a Lewis acid.The process is analogous to the reaction of S 8 with sodium sulfide (which forms polysulfides) except that the higher polyiodides have branched structures.
Ammonium triiodide [1] [2] (NH 4 I 3) is the salt of the ammonium cation with the triiodide anion. Sometimes the name ammonium triiodide is mistakenly used to refer to a different compound, nitrogen triiodide (NI 3 ), or more precisely, the slightly more stable ammine , NI 3 · NH 3 .