The hypoiodous acid, also known as monoxoyodato (I) hydrogen or yodol, is an inorganic compound of formula HIO. It is an oxacid of iodine, with an oxygen atom, a hydrogen atom and an iodine atom with a 1+ oxidation state.
The compound is very unstable since it tends to undergo a dismutation reaction where it is reduced to molecular iodine and oxidized to iodine acid according to the reaction: 5HIO → 2I 2 + HIO 3 + 2H 2 O.
Figure 1: structure of hypoiodoid acid.
The compound is the weakest acid of the halogen oxacids with oxidation state 1+. The corresponding salts of this acid are known as hypoiodites.
These salts are more stable than acid and are formed in a similar manner to their chlorine and bromine counterparts, by reacting molecular iodine with alkali or alkaline earth metal hydroxides.
Hypo-iodine acid is produced by reacting molecular iodine with mercury (II) oxide (Egon Wiberg, 2001) according to the reaction:
2I 2 + 3HgO + H 2 O → 2HIO + HgI 2 2HgO
Traces of the compound are also obtained by reacting molecular iodine with potassium hydroxide to form, initially potassium iodide and potassium hypoiodite according to the reaction:
I 2 + 2KOH → KI + KIO
However, hypoiodine acid, being such a weak acid, makes hydrolyzing of potassium hypoiodite feasible unless there is excess potassium hydroxide (Holmyard, 1922).
KIO + H 2 O → HIO + KOH
It can also be obtained, like its chlorine and bromine counterparts, by reacting molecular iodine with water. However, given its low equilibrium constant, which is in the order of 10 -13, the quantities obtained are very small (RG Compton, 1972).
Physical and chemical properties
Hypoiodine acid only exists as an aqueous solution which is yellowish in color. The compound in solid state has not been able to isolate, so most of its properties are theoretically obtained through computational calculations (National Center for Biotechnology Information, 2017).
Hypoiodine acid has a molecular weight of 143.911 g / mol, a melting point of 219.81 ° C, a boiling point of 544.27 ° C, and a vapor pressure of 6.73 x 10 -14 millimeters of mercury.
The molecule is very soluble in water, being able to dissolve between 5.35 x 10 5 and 8.54 x 10 5 grams of compound per liter of this solvent (Royal Society of Chemistry, 2015).
HOI is a strong oxidant and can form explosive mixtures. It is also a reducing agent and can be oxidized to the iodine, iodic and periodic forms of the acid. In aqueous solutions, being a weak acid, it partially dissociates into the hypoiodite ion (OI -) and H +.
HOI reacts with bases to form salts called hypoiodites. For example, sodium hypoiodite (NaOI) is formed by reacting hypoiodine acid with sodium hydroxide.
HOI + NaOH → NaOI + H 2 O
Hypoiodine acid also easily reacts with a variety of organic molecules and biomolecules.
Reactivity and hazards
Hypoiodine acid is an unstable compound decomposing to elemental iodine. Iodine is a toxic compound that must be handled with care.
Hypoiodine acid is dangerous in case of contact with the skin (irritant), in contact with the eyes (irritant) and in cases of ingestion and inhalation.
In case of contact with the eyes, check if you are wearing contact lenses and remove them immediately. Eyes should be flushed with running water for at least 15 minutes, keeping the eyelids open. Cold water can be used. Eye ointment should not be used.
If the chemical comes into contact with clothing, remove it as quickly as possible, protecting your own hands and body. Place the victim under a safety shower.
If the chemical accumulates on the victim's exposed skin, such as hands, the contaminated skin is gently and carefully washed with running water and non-abrasive soap. Cold water can be used. If irritation persists, seek medical attention. Wash the contaminated clothing before using it again.
If the contact with the skin is severe, it should be washed with a disinfectant soap and cover the contaminated skin with an antibacterial cream.
In case of inhalation, the victim should be allowed to rest in a well-ventilated area. If inhalation is severe, the victim should be evacuated to a safe area as soon as possible. Loosen tight clothing such as a collar, belt, or tie.
If it is difficult for the victim to breathe, oxygen should be administered. If the victim is not breathing, mouth-to-mouth resuscitation is performed. Always keeping in mind that it can be dangerous for the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive.
In case of ingestion, do not induce vomiting. Loosen tight clothing such as shirt collars, belts, or ties. If the victim is not breathing, perform mouth-to-mouth resuscitation.
In all cases, immediate medical attention should be sought.
Applications
Hypoiodine acid is used as a powerful oxidizing agent and as a reducing agent in laboratory reactions. It is used to produce chemical compounds known as hypoiodites.
Spectrophotometric methods are also used to measure hypoiodine acid formation to monitor reactions where iodine is involved (TL Allen, 1955).
Halides are incorporated into aerosols, where they begin the catalytic destruction of ozone (O 3) over the oceans and affect the global troposphere. Two intriguing environmental issues undergoing ongoing investigation are: understanding how molecular halogens in the reactive gas phase are produced directly from inorganic halides exposed to O 3 and restricting the environmental factors that control this interfacial process.
In the work of (Elizabeth A. Pillar, 2013) the conversion of iodide to hypoiodine acid by the action of ozone was measured through mass spectroscopy measurements to determine a model of ozone depletion in the atmosphere.
References
- Egon Wiberg, NW (2001). Inorganic Chemistry. London: Academic press.
- Elizabeth A. Pillar, MI (2013). Conversion of Iodide to Hypoiodous Acid and Iodine in Aqueous Microdroplets Exposed to Ozone. Sci. Technol., 47 (19), 10971-10979.
- EMBL-EBI. (2008, January 5). hypoiodous acid. Retrieved from ChEBI: ebi.ac.uk.
- Holmyard, E. (1922). Inorganic chemistry. London: Edwar Arnol & co.
- National Center for Biotechnology Information.. (2017, April 22). PubChem Compound Database; CID = 123340. Retrieved from PubChem.
- G. Compton, CB (1972). Reactions of Non-Metallic Inorganic Compounds. Ansterdam: Elsevier Publishing Company.
- Royal Society of Chemistry. (2015). Iodol. Retrieved from chemspider.com.
- L. Allen, RM (1955). The Formation of Hypoiodous Acid and Hydrated Iodine Cation by the Hydrolysis of Iodine. J. Am. Chem. Soc., 77 (11), 2957-2960.