The perbromic acid or bromic acid is an inorganic tetraoxo compound of formula HBrO 4. Its structure is presented in figure 1 (EMBL-EBI, 2007). It is an oxacid bromine acid, where it has a 7+ oxidation state.
It is unstable and cannot be formed by displacement of chlorine from perchloric acid as perbromic acid is prepared; it can only be done by protonation of the perbromate ion.
Perbromic acid is a strong acid and powerful oxidizing agent. It is the least stable of the halogen oxacids (VII). It decomposes rapidly to bromic acid and oxygen releasing toxic brown bromine fumes.
Its conjugate base is the perbromate ion which, unlike perchlorates, is not accessible by electrolysis. It is formed by reacting bromates with ozone or when perbromic acid reacts with bases (Ropp, 2013). A new synthesis of perbromates has been developed, which consists of the oxidation of bromate with fluorine in alkaline solution.
BrO 3 - + F 2 + H 2 O → BrO 4 - + HF
It was discovered by the decay of a radioactive selenate sample (SeO 4 -). The compound is also produced by exposing bromate crystals to γ radiation (AJ Downs, 1973)
Perbromic acid is a strong monobasic acid. Their aqueous solutions are stable up to approximately 6 M (55% HBrO4) but decompose at higher concentrations (Appelman, 1969).
Physical and chemical properties
Perbromic acid exists only in solution. It is a colorless liquid without a characteristic aroma (National Center for Biotechnology Information, 2017).
The compound has a molecular weight of 144.908 g / mol. Given its instability, its properties were calculated by computational methods, obtaining a melting and boiling point of 204.77 ° C and 512.23 ° C respectively.
Its solubility in water, also obtained through computational calculations, is in the order of 1 x 10 6 mg per liter at 25 ° C (Royal Society of Chemistry, 2015). Perbromic acid is a strong acid, having only one proton for each heptavalent bromine atom. In aqueous solution, the hydronium ion and BrO 4 - are completely dissociated.
Solutions with concentrations greater than 6M (55% w / v) are unstable in air, an autocatalytic decomposition of the compound occurs, which is complete at concentrations of 80%. This decomposition reaction is also catalyzed by metals such as Ce 4+ and Ag + (Egon Wiberg, 2001).
Reactivity and hazards
Perbromic acid is an unstable compound, however it has strong acid properties when isolated. It is extremely dangerous in case of contact with the skin (it is corrosive and irritant), in contact with the eyes (irritant) and in case of ingestion. Also very dangerous in case of inhalation.
Severe overexposure can cause lung damage, suffocation, loss of consciousness, or death. Prolonged exposure can cause skin burns and ulcerations. Inhalation overexposure may cause respiratory irritation.
Inflammation of the eye is characterized by redness, watering, and itching. Inflammation of the skin is characterized by itching, peeling, redness, and occasionally blistering.
The substance is toxic to the kidneys, lungs and mucous membranes. Repeated or prolonged exposure to the substance can damage these organs.
In case of contact with the eyes, check if contact lenses are being used 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.
You can also neutralize the acid with dilute sodium hydroxide or with a weak base such as baking soda. 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 taking into account 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
The main use of perbromic acid is as a reducing agent in the laboratory. Dilute solutions of perbromic acid are slow oxidizing agents despite their great potential REDOX (+1.76 volts) however it is a better oxidant than perchloric acid.
Perbromic acid can slowly oxidize bromide and iodide ions. In solutions of 12 molar concentration, it can rapidly oxidize the chloride ion and explode in the presence of nitric acid. Solutions of 3 molar concentration of perbromic acid can easily oxidize stainless steel.
At a temperature of 100 ° C, 6 molar solutions of perbromic acid can oxidize manganese ion (Mn 2+) to permanganate (MnO 4 -). Reduction of the compound to bromine can be accomplished with tin chloride (SnO 2).
The other use of perbromic acid is the synthesis of perbromate salts such as sodium perbromate or potassium perbromate.
The latter is a fairly stable compound that resists temperatures of 274 ° C. At higher temperatures it is reduced to potassium bromate, unlike perchlorate which at high temperatures produces oxygen and potassium chloride.
References
- J. Downs, CJ (1973). The Chemistry of Chlorine, Bromine, Iodine and Astatine. Oxford: Pergamon press LTD.
- Appelman, EH (1969). Perbromic acid and perbromates: Synthesis and some properties. Inorganic Chemistry 8 (2) ·, 223–227. Recovered from researchgate.net.
- Egon Wiberg, NW (2001). Inorganic Chemistry. New York: Academic Press.
- EMBL-EBI. (2007, October 28). perbromic acid. Recovered from ebi.ac.uk.
- National Center for Biotechnology Information. (2017, April 30). PubChem Compound Database; CID = 192513. Recovered from pubchem.ncbi.nlm.nih.gov.
- Ropp, RC (2013). Encyclopedia of the Alkaline Earth Compounds. Oxford: Elsevier.
- Royal Society of Chemistry. (2015). Perbromic acid. Recovered from chemspider.com.