Halous acid

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A halous acid, also known as a halogenous acid, [1] is an oxyacid consisting of a halogen atom in the +3 oxidation state single-bonded to a hydroxyl group and double-bonded to an oxygen atom. Examples include chlorous acid, bromous acid, and iodous acid. The conjugate base is a halite.

Contents

Synthesis

One method is to add oxygen to the corresponding hypohalous acid. This can be done with another hypohalous acid—or even the same one.

HBrO + HClO → HBrO2 + HCl [2]
2  HBrO → HBrO2 + HBr [2]

The latter is a disproportionation reaction.

Another method of oxidizing hypobromous acid can be used:

HBrO + H2O - 2e− → HBrO2 + 2H+ [2]

The oxidized bromine-containing acid need not contain oxygen originally, as in this comproportionation reaction:

2 HBrO3 + HBr → 3 HBrO2 [2]

Bromous acid was originally prepared using another method of adding oxygen to hypobromous acid, where the free oxygen was freed from water when the free hydrogen was taken by NO3 (to form nitric acid) that was freed from silver nitrate when the silver was taken by elemental bromine to form silver bromide.

2 AgNO3 + HBrO + Br2 + H2O → HBrO2 + 2 AgBr [3]

Chlorous acid may be generated from salts of the conjugate base, chlorite, which is more stable than chlorous acid. [4]

Ba(ClO2)2 + H2SO4 → BaSO4 + 2 HClO2 [5]

Stability

Chlorous acid, bromous acid, and iodous acid are all unstable. Chlorous acid is the only isolatable halous acid, [6] and while it has stable salts, they tend to decompose rapidly, some even explosively, upon heating. [4] Neither bromous acid nor iodous acid has ever been isolated, and while a few salts of bromous acid have been isolated, the same is not true for iodous acid. [6]

One method of decomposition of halous acids is disproportionating to the corresponding hypohalous acid and halic acid:

2 HClO2 → HClO + HClO3
2 HBrO2 → HBrO3 + HOBr

In acidic solutions, chlorous acid tends to decompose via another disproportionation reaction:

5 HClO2 → 4 ClO2 + HCl + 2 H2O [5]

Related Research Articles

In chemistry, perxenates are salts of the yellow xenon-containing anion XeO4−
6. This anion has octahedral molecular geometry, as determined by Raman spectroscopy, having O–Xe–O bond angles varying between 87° and 93°. The Xe–O bond length was determined by X-ray crystallography to be 1.875 Å.

Chloric acid Chemical compound

Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pKa ≈ −2.7) and oxidizing agent.

Sodium thiosulfate Chemical compound

Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula Na2S2O3.xH2O. Typically it is available as the white or colorless pentahydrate, Na2S2O3·5H2O. The solid is an efflorescent (loses water readily) crystalline substance that dissolves well in water.

Hydrazoic acid Unstable and toxic chemical compound

Hydrazoic acid, also known as hydrogen azide or azoimide, is a compound with the chemical formula HN3. It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, and is therefore a pnictogen hydride. It was first isolated in 1890 by Theodor Curtius. The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.

Chlorous acid Chemical compound

Chlorous acid is an inorganic compound with the formula HClO2. It is a weak acid. Chlorine has oxidation state +3 in this acid. The pure substance is unstable, disproportionating to hypochlorous acid (Cl oxidation state +1) and chloric acid (Cl oxidation state +5):

Gold(III) chloride Chemical compound

Gold(III) chloride, traditionally called auric chloride, is a compound of gold and chlorine with the molecular formula Au2Cl6. The "III" in the name indicates the gold has an oxidation state of +3, which is typical for many gold compounds. Gold(III) chloride is hygroscopic and decomposes in visible light. This compound is a dimer of AuCl3. This compound has few uses, although it does catalyze a variety of organic reactions.

Perbromate Ion

In chemistry, the perbromate ion is the anion having the chemical formula BrO−
4. It is an oxyanion of bromine, the conjugate base of perbromic acid, in which bromine has the oxidation state +7. Unlike its chlorine and iodine analogs, it is difficult to synthesize. It has tetrahedral molecular geometry.

Beryllium nitride Chemical compound

Beryllium nitride, Be3N2, is a nitride of beryllium. It can be prepared from the elements at high temperature (1100–1500 °C), unlike Beryllium azide or BeN6, it decomposes in vacuum into beryllium and nitrogen. It is readily hydrolysed forming beryllium hydroxide and ammonia. It has two polymorphic forms cubic α-Be3N2 with a defect anti-fluorite structure, and hexagonal β-Be3N2. It reacts with silicon nitride, Si3N4 in a stream of ammonia at 1800–1900 °C to form BeSiN2.

Hypobromous acid Chemical compound

Hypobromous acid is a weak, unstable acid with chemical formula of HOBr. It is mainly produced and handled in an aqueous solution. It is generated both biologically and commercially as a disinfectant. Salts of hypobromite are rarely isolated as solids.

Xenic acid is a noble gas compound formed by the dissolution of xenon trioxide in water. Its chemical formula is H2XeO4. It is a very powerful oxidizing agent, and its decomposition is dangerous as it liberates a large amount of gaseous products: xenon, oxygen, and ozone. However, this feature is also what makes xenic acid practically useful in syntheses: there is no chance of introducing impurities to the oxidation products, as all the byproducts can be trivially evaporated.

Phosphorus trioxide Chemical compound

Phosphorus trioxide is the chemical compound with the molecular formula P4O6. Although the molecular formula suggests the name tetraphosphorus hexoxide, the name phosphorus trioxide preceded the knowledge of the compound's molecular structure, and its usage continues today. This colorless solid is structurally related to adamantane. It is formally the anhydride of phosphorous acid, H3PO3, but cannot be obtained by the dehydration of the acid. A white solid that melts at room temperature, it is waxy, crystalline and highly toxic, with garlic odour.

Hypoiodous acid is the inorganic compound with the chemical formula HIO. It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:

Bromous acid Chemical compound

Bromous acid is the inorganic compound with the formula of HBrO2. It is an unstable compound, although salts of its conjugate base – bromites – have been isolated. In acidic solution, bromites decompose to bromine.

Disulfurous acid Chemical compound

Disulfurous acid or pyrosulfurous acid is an oxoacid of sulfur with the formula H2S2O5. The salts of disulfurous acid are called disulfites or metabisulfites. Disulfurous acid is, like sulfurous acid (H2SO3), a phantom acid, which does not exist in the free state. In contrast to disulfate (S
2O−
7), disulfite has two directly connected sulfur atoms. The oxidation state of the sulfur atom bonded to three oxygen atoms is +5 while that of the other is +3.

Polonium dioxide Chemical compound

Polonium dioxide (also known as polonium(IV) oxide) is a chemical compound with the formula PoO2. It is one of three oxides of polonium, the other two being polonium monoxide (PoO) and polonium trioxide (PoO3). It is a pale yellow crystalline solid at room temperature. Under lowered pressure (such as a vacuum), it decomposes into elemental polonium and oxygen at 500 °C. It is the most stable oxide of polonium and is an interchalcogen.

Dibromine monoxide Chemical compound

Dibromine monoxide is the chemical compound composed of bromine and oxygen with the formula Br2O. It is a dark brown solid which is stable below −40°C and is used in bromination reactions. It is similar to dichlorine monoxide, the monoxide of its halogen neighbor one period higher on the periodic table. The molecule is bent, with C2v molecular symmetry. The Br−O bond length is 1.85Å and the Br−O−Br bond angle is 112°, similar to dichlorine monoxide.

Metal peroxide

Metal peroxides are metal-containing compounds with ionically- or covalently-bonded peroxide (O2−
2) groups. This large family of compounds can be divided into ionic and covalent peroxide. The first class mostly contains the peroxides of the alkali and alkaline earth metals whereas the covalent peroxides are represented by such compounds as hydrogen peroxide and peroxymonosulfuric acid (H2SO5). In contrast to the purely ionic character of alkali metal peroxides, peroxides of transition metals have a more covalent character.

A hypohalous acid is an oxyacid consisting of a hydroxyl group single-bonded to any halogen. Examples include hypofluorous acid, hypochlorous acid, hypobromous acid, and hypoiodous acid. The conjugate base is a hypohalite. They can be formed by reacting the corresponding diatomic halogen molecule (F2, Cl2, Br2, I2) with water in the reaction:

Halite (oxyanion)

A halite, also known as a halogenite, is an oxyanion containing a halogen in a III oxidation state. It is the conjugate base of a halous acid. The known halites are chlorite, bromite, and iodite.

Polonium sulfide is an inorganic compound of polonium and sulfur with the chemical formula PoS. The compound is radioactive, forms black crystals.

References

  1. ↑ Holleman, A. F.; Wiberg, Egon; Wiberg, Nils (2001). Inorganic Chemistry. Web: Academic Press. p. 439. ISBN   9780123526519 . Retrieved 21 March 2019.
  2. 1 2 3 4 C., Ropp, R. (2013-01-01). Encyclopedia of the alkaline earth compounds. Elsevier. ISBN   9780444595508. OCLC   964753424.
  3. ↑ "Journal of the Society of Chemical Industry. v.25 1906". HathiTrust. Retrieved 2017-04-28.
  4. 1 2 Holleman, A. F.; Wiberg, Egon; Wiberg, Nils (2001). Inorganic Chemistry. Web: Academic Press. p. 445. ISBN   9780123526519 . Retrieved 21 March 2019.
  5. 1 2 Holleman, A. F.; Wiberg, Egon; Wiberg, Nils (2001). Inorganic Chemistry. Web: Academic Press. p. 444. ISBN   9780123526519 . Retrieved 21 March 2019.
  6. 1 2 Wiberg, Egon; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Elsevier. ISBN   0-12-352651-5.[ page needed ]
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