- Physical and chemical properties
- Reactivity and hazards
- Handling and storage
- Synthesis
- Applications
- References
The hydrogen bromide, a compound of formula HBr chemical is a diatomic molecule with a covalent bond. The compound is classified as a hydrogen halide, being a colorless gas that, when dissolved in water, forms hydrobromic acid, saturating itself at 68.85% w / p at room temperature.
Aqueous solutions at 47.6% w / w form a constant boiling azeotropic mixture boiling at 124.3 degrees centigrade. Less concentrated, boiling solutions release H2O until the composition of the constant-boiling azeotropic mixture is reached.
Figure 1: Structure of hydrogen bromide.
Physical and chemical properties
Hydrogen Bromide is a colorless gas at room temperature with a sour, irritating odor. The compound is stable, but gradually darkens when exposed to air or light as illustrated in Figure 2 (National Center for Biotechnology Information, SF).
Figure 2: appearance of hydrogen bromide.
It has a molecular weight of 80.91 g / mol and a density of 3.307 g / L, which makes it heavier than air. The gas condenses producing a colorless liquid with a boiling point of -66.73 degrees Celsius.
As it continues to cool, the liquid solidifies, obtaining white crystals, whose melting point is -86.82 degrees Celsius with a density of 2.603 g / ml (Egon Wiberg, 2001). The appearance of these crystals is illustrated in Figure 3.
Figure 3: appearance of hydrogen bromide.
The bond distance between bromine and hydrogen is 1.414 angstroms and their dissociation energy is 362.5 kJ / mol.
Hydrogen bromide is more soluble in water than hydrogen chloride, 221 g can be dissolved in 100 ml of water at 0 degrees Celsius, which is equivalent to a volume of 612 liters of this gas for each liter of water. It is also soluble in alcohol and other organic solvents.
In aqueous solution (hydrobromic acid) the acidic properties of HBr are dominant, (as is the case of HF and HCl) and, in the bond between hydrogen and halogen, it is weaker in the case of hydrogen bromide than in hydrogen chloride.
Therefore, if chlorine is passed through hydrogen bromide, the formation of brown vapors characteristic of molecular bromine is observed. The reaction that explains it is the following:
2HBr + Cl2 → 2HCl + Br2
This is indicative that hydrogen bromide is a stronger reducing agent than hydrogen chloride and that hydrogen chloride is a better oxidizing agent.
Hydrogen bromide is a strong anhydrous acid (without water). Reacts quickly and exothermically with bases of all kinds (including amines and amides).
Reacts exothermically with carbonates (including limestone and limestone-containing building materials) and hydrogen carbonates to generate carbon dioxide.
Reacts with sulfides, carbides, borides, and phosphides to generate flammable or toxic gases.
Reacts with many metals (including aluminum, zinc, calcium, magnesium, iron, tin, and all alkali metals) to generate flammable hydrogen gas.
Respond violently with:
- acetic anhydride
- 2-aminoethanol
- ammonium hydroxide
- calcium phosphide
- chlorosulfonic acid
- 1,1-difluoroethylene
- ethylenediamine
- ethyleneimine
- fuming sulfuric acid
- perchloric acid
- b-propriolactone
- propylene's OXID
- silver perchlorate
- Uranium (IV) phosphide
- vinyl acetate
- calcium carbide
- rubidium carbide
- cesium acetylide
- rubidium acetylide
- magnesium boride
- mercury (II) sulfate
- calcium phosphide
- calcium carbide (Chemical Datasheet, 2016).
Reactivity and hazards
Hydrogen bromide is classified as a corrosive and irritant compound. It is extremely dangerous in case of contact with the skin (irritant and corrosive) and the eyes (irritant) and in cases of ingestion and inhalation (lung irritant).
The compound is stored in pressurized liquefied gas containers. Prolonged exposure to fire or intense heat can result in the violent rupture of the pressurized container, which can be released releasing irritating toxic fumes.
Prolonged exposure to low concentrations or short-term exposure to high concentrations can result in adverse health effects due to inhalation.
Thermal decomposition of anhydrous hydrogen bromide produces toxic bromine gases. It can become flammable if it reacts by releasing hydrogen. In contact with cyanide it produces toxic hydrogen cyanide gases.
Inhalation causes severe irritation of the nose and upper respiratory tract, which may cause lung injury.
Ingestion causes burns in the mouth and stomach. Contact with the eyes causes severe irritation and burns. Contact with the skin causes irritation and burns.
If this chemical in solution comes into contact with the eyes, they should be flushed immediately with large amounts of water, occasionally lifting the lower and upper eyelids.
Contact lenses should not be worn when working with this chemical. If eye tissue is frozen, seek immediate medical attention.
If the tissue is not frozen, immediately and thoroughly rinse the eyes with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper lids.
If irritation, pain, swelling or tearing persists get medical attention as soon as possible.
If this chemical in solution comes into contact with skin and does not cause frostbite, immediately rinse contaminated skin with water.
If this chemical gets on clothing, immediately remove clothing and wash skin with water.
If frostbite occurs, seek medical attention immediately. Do not rub affected areas or rinse with water. In order to prevent further damage to fabrics, no attempt should be made to remove frozen clothing from frosty areas.
If large amounts of this chemical are inhaled, the exposed person should be moved to fresh air immediately. If breathing has stopped, perform mouth-to-mouth resuscitation. The victim should be kept warm and at rest, and medical attention should be sought as soon as possible.
If this chemical in solution has been swallowed, get medical attention immediately.
Handling and storage
Hydrogen bromide cylinders should be stored in a cool, well-ventilated place. Its handling must be with adequate ventilation. It should only be stored when the temperature does not exceed 52 degrees Celsius.
Containers must be firmly secured in an upright position to prevent them from falling or being struck. Also, install the valve protective cap, if provided, firmly in place by hand, as well as store full and empty containers separately (praxair inc., 2016).
When handling product under pressure, properly designed plumbing and equipment should be used to withstand the pressures encountered. Never work on a pressurized system and use a backflow prevention device in the pipeline. Gases can cause rapid suffocation due to oxygen deficiency.
Store and use with adequate ventilation is important. If a leak occurs, close the container valve and shut down the system in a safe and environmentally sound manner. Then repair the leak. Never place a container where it can be part of an electrical circuit.
Leather safety gloves and suitable shoes should be worn when handling cylinders. These must be protected and for this they must be avoided, dragged, rolled or slid.
When moving the cylinder, the removable valve cover should always be kept in place. Never attempt to lift a cylinder by its cap, which is intended solely to protect the valve.
When moving cylinders, even for short distances, use a cart (cart, hand truck, etc.) designed to transport cylinders.
An object (eg spanner, screwdriver, pry bar) should never be inserted into the openings in the cover as doing so may damage the valve and cause a leak.
An adjustable strap wrench is used to remove caps that are too tight or rusted. The valve should open slowly and if this is impossible, stop using it and contact your supplier. Of course, the container valve must be closed after each use.
Said container must be kept closed even when empty. Flame or localized heat should never be applied directly to any part of the container. High temperatures can damage the container and cause the pressure relief device to fail prematurely, venting the contents of the container (praxair inc., 2016).
Synthesis
Gaseous hydrogen bromide can be manufactured in the laboratory by brominating tetralin (1,2,3,4-tetrahydronaphthalene). The downside is that half of the bromine is lost. The yield is approximately 94%, or what is the same, 47% of the bromine ends up as HBr.
C 10 H 12 + 4 Br 2 → C 10 H 8 Br 4 + 4 HBr
Hydrogen bromide gas can also be synthesized in the laboratory by reacting concentrated sulfuric acid with sodium bromide.
NaBr (s) + H 2 SO 4 → HBr (g) + NaHSO 4
The disadvantage of this method is that much of the product is lost by oxidation with excess sulfuric acid to form bromine and sulfur dioxide.
2 HBr + H 2 SO 4 → Br 2 + SO 2 + 2 H 2 O
Hydrogen bromide can be prepared in the laboratory by the reaction between purified hydrogen gas and bromine. This is catalyzed by platinum asbestos and is carried out in a quartz tube at 250 ° C.
Br 2 + H 2 → 2 HBr
Anhydrous hydrogen bromide can also be produced on a small scale by thermolysis of triphenylphosphonium bromide in xylene under reflux.
HBr can be obtained by the red phosphorous method. First, the red phosphorus is added in the water reactor and later, slowly, the bromine under stirring and the reaction of hydrobromic acid and phosphorous acid, by sedimentation, filtration and the distillation obtained will be hydrobromic acid.
P 4 +6 Br 2 +12 H 2 O → 12 HBr + 4 H 3 PO 3
Hydrogen bromide prepared by the above methods can become contaminated with Br 2, which can be removed by passing the gas through a solution of phenol in tetrachloromethane or other suitable solvent at room temperature, producing 2, 4, 6-tribromophenol and thereby generating plus HBr.
This process can also be carried out through high temperature copper chips or copper gauze (Hydrogen: hydrogen bromide, 1993-2016).
Applications
HBr is used in the manufacture of organic bromides, such as methyl bromide, bromoethane, etc., and inorganic ones, such as sodium bromide, potassium bromide, lithium bromide, and calcium bromide, etc.
It is also used in photographic and pharmaceutical applications or for the synthesis of sedatives and anesthetics. In addition, it is applied in industrial drying, textile finishing, coating agents, surface treatment agents and fireproofing.
The compound is also used to etch polysilicon sheets, for the manufacture of computer chips (Interscan Corporation, 2017).
Hydrogen bromide is a good solvent for some metallic minerals, used in the refinement of high-purity metals.
In the petroleum industry, it is used as a separation of alkoxy and phenoxy compounds, and a catalyst for the oxidation of cyclic hydrocarbons and chain hydrocarbons to ketones, acid or peroxide. It is also used in synthetic dyes and spices.
A high quality gas from HBr is used for etching and cleaning for semiconductor raw material (SHOWA DENKO KK, nd).
The compound is used as an analytical reagent in the determination of sulfur, selenium, bismuth, zinc and iron, for the separation of tin from arsenic and antimony. It is an alkylation catalyst and reducing agent used in organic synthesis.
Hydrogen bromide can be used for the production of hydrobromic acid. Hydrobromic acid is a very strong mineral acid, stronger than hydrochloric acid.
HBr is highly reactive and corrosive to most metals. Acid is a common reagent in organic chemistry, used for oxidation and catalysis. It is also effective in the extraction of certain metallic minerals (Hydrogen bromide, 2016).
References
- Interscan Corporation. (2017). Hydrogen Bromide-and Hydrogen Bromide Monitoring Instrumentation. Retrieved from gasdetection.com.
- Chemical Datasheet. (2016). Retrieved from HYDROGEN BROMIDE, ANHYDROUS: cameochemicals.noaa.gov.
- Egon Wiberg, NW (2001). Inorganic Chemistry. Academic press.
- Hydrogen bromide. (2016). Retrieved from ChemicalBook.
- Hydrogen: hydrogen bromide. (1993-2016). Retrieved from WebElements.
- Material Safety Data Sheet Hydrogen bromide. (2005, October 9). Retrieved from sciencelab.com.
- National Center for Biotechnology Information. (SF). PubChem Compound Database; CID = 260. Retrieved from pubchem.ncbi.nlm.nih.gov.
- praxair inc. (2016, October 17). Hydrogen bromide, anhydrous Safety Data Sheet P-4605. Retrieved from praxair.com.
- SHOWA DENKO KK (nd). hydrogen bromide. Retrieved from www.sdk.co.jp.