Everything about Iodide totally explained
An
iodide ion is an
iodine atom with a −1
charge . Compounds with iodine in formal
oxidation state −1 are called
iodides. This can include
ionic compounds such as
caesium iodide or
covalent compounds such as
carbon tetraiodide. This is the same naming scheme as is seen with
chlorides and
bromides. The chemical test for an iodide compound is to acidify the aqueous compound by adding some drops of
acid, to dispel any carbonate ions present, then adding
lead(II) nitrate, yielding a bright yellow
precipitate of
lead iodide. Most ionic iodides are soluble, with the exception of yellow
silver iodide and yellow
lead iodide. Aqueous solutions of iodide dissolve iodine better than pure water due to the formation of
complex ions:
» I
−(aq) + I
2(s) ⇌ I
3−(aq)
The colour of new
triiodide ions formed are brown.
Examples
Examples or common iodides include:
Iodide as an antioxidant
Iodide can function as an antioxidant as it's a
reducing species that can detoxify
reactive oxygen species such as
hydrogen peroxide. Over three billion years ago,
blue-green algae were the most primitive oxygenic
photosynthetic organisms and are the ancestors of multicellular
eukaryotic algae (1). Algae that contain the highest amount of iodine (1-3 % of dry weight) and peroxidase enzymes, were the first living cells to produce poisonous oxygen in the atmosphere . Therefore algal cells required a protective antioxidant action of their molecular components, in which iodides, through peroxidase enzymes, seem to have had this specific role
. In fact, iodides are greatly present and available in the sea, where algal phytoplankton, the basis of marine food-chain, acts as a biological accumulator of iodides, selenium, (and n-3 fatty acids) :
Antioxidant biochemical mechanism of iodides
» 2 I
− → I
2 + 2 e
− (electrons) = −0.54 Volt ;
2 I
− + Peroxidase + H
2O
2 + 2 Tyrosine → 2 Iodo-Tyrosine + H
2O + 2 e
− (antioxidants);
» 2 e
− + H
2O
2 + 2 H
+ (of intracellular water-solution) → 2 H
2O
Antioxidant biochemical mechanism of iodides, probably one of the most ancient mechanisms of defense from poisonous reactive oxygen species:
» 2 I
− + Peroxidase + H
2O
2 + Tyrosine, Histidine, Lipids, Carbons -> Iodo-Compounds + H
2O + 2 e
− (antioxidants)
Iodo-Compounds: Iodo-Tyrosine, Iodo-Histidine, Iodo-Lipids, Iodo-Carbons.
Clinical Use
Iodide (>6mg/day) can be used to treat patients with
hyperthyroidism due to its ability to block the release of
thyroid hormone (TH), known as the Wolff-Chaikoff Effect, from the
thyroid gland. In fact, prior to
1940, iodides were the predominant antithyroid agents. In large doses, iodides inhibit
proteolysis of
thyroglobulin. This permits TH to be synthesized and stored in
colloid, but not released into the bloodstream.
Of note, this treatment is seldom used today as a stand-alone therapy despite the rapid improvement of patients immediately following administration. The major disadvantage of iodide treatment lies in the fact that excessive stores of TH accumulate, slowing the onset of action of
thioamides (TH synthesis blockers). Additionally, the functionality of iodides fade after the initial treatment period. An "escape from block" is also a concern, as extra stored TH may spike following discontinuation of treatment.
Further Information
Get more info on 'Iodide'.
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