He Hydrogen bromide , A chemical compound of the formula HBr, is a diatomic molecule with a covalent bond. The compound is classified as a hydrogen halide, a colorless gas being, when dissolved in water, forms hydrobromic acid saturating at 68.85% w / w at room temperature.
Aqueous solutions at 47.6% w / w form a constant boiling azeotropic mixture boiling at 124.3 degrees centigrade. The 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 of hydrogen bromide
Hydrogen bromide is a colorless gas at room temperature with a sour, irritating odor. The compound is stable, but dims little by little when exposed to air or light as illustrated in Figure 2 (National Center for Biotechnology Information, S.F.).
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 is condensed to produce a colorless liquid with a boiling point of -66.73 degrees Celsius.
Upon further cooling, the liquid solidifies to white crystals, which melting point is -86.82 degrees centigrade 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 angstrom and its dissociation energy is 362.5 kJ / mol.
Hydrogen bromide is more soluble in water than hydrogen chloride, and 221 g in 100 ml of water at 0 degrees Celsius can be dissolved, which is equivalent to a volume of 612 liters of this gas per 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 hydrogen-halogen bond, 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).
It reacts exothermically with carbonates (including limestone and building materials containing limestone) and hydrogen carbonates to generate carbon dioxide.
Reactions with sulfides, carbides, borides and phosphides to generate toxic or flammable 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-propiolactone
- propylene's OXID
- Silver perchlorate
- Uranium phosphate (IV)
- Vinyl acetate
- Calcium carbide
- Rubidium carbide
- Cesium acetylide
- Rubidium acetylide
- Magnesium boride
- Mercury sulfate (II)
- 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 skin contact (irritant and corrosive) and eyes (irritant) and in cases of ingestion and inhalation (pulmonary irritant).
The compound is stored in pressurized liquefied gas containers. Prolonged exposure to fire or severe heat may result in the violent rupture of the pressurized container, which may be released by releasing toxic irritant vapors.
Prolonged exposure to low concentrations or short-term exposure to high concentrations may 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 produces toxic gases of hydrogen cyanide.
Inhalation causes severe irritation of the nose and upper respiratory tract, resulting in lung injury.
Ingestion causes burns to the mouth and stomach. Contact with eyes causes severe irritation and burns. Contact with skin causes irritation and burns.
If this chemical solution comes into contact with the eyes, they should be washed immediately with large amounts of water, occasionally raising 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 tissue is not frozen, flush eyes immediately and thoroughly with large amounts of water for at least 15 minutes, occasionally lifting lower and upper eyelids.
If irritation, pain, swelling or tearing persists get medical attention as soon as possible.
If this chemical in solution comes into contact with the skin and does not cause frostbite, immediately rinse skin contaminated with water.
If this chemical penetrates into clothing, immediately remove clothing and wash skin with water.
If frostbite occurs, seek medical attention immediately. Do not rub the affected areas or rinse with water. In order to prevent further tissue damage, do not attempt to remove frozen clothing from areas with frost.
If large quantities 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, in addition to seeking medical attention as soon as possible.
If this chemical solution has been swallowed, get medical attention immediately.
Handling and storage
Hydrogen bromide cylinders should be stored in a cool, well-ventilated place. Handling should be with adequate ventilation. It should be stored only when the temperature does not exceed 52 degrees centigrade.
The containers should be firmly secured in an upright position to prevent them from falling or being struck. In addition, install the protective cap of the valve, if fitted, firmly in place by hand, as well as storing full and empty containers separately (praxair inc., 2016).
When handling the product under pressure, pipelines and equipment suitably designed to withstand the pressures encountered should be used. Never work on a pressurized system and use a return flow prevention device in the pipeline. Gases can cause rapid asphyxia due to oxygen deficiency.
Storage and use with adequate ventilation is important. If a leak occurs, close the valve on the container and turn off the system in a safe and environmentally correct manner. Then repair the leak. Never place a receptacle where it may be part of an electrical circuit.
Proper leather safety gloves and shoes should be worn when handling cylinders. These must be protected and for this you should avoid dragging, rolling or sliding.
When moving the cylinder, always keep the removable valve cap in place. Never attempt to lift a cylinder by its cap, which is intended only to protect the valve.
When moving cylinders, even for short distances, use a cart (trolley, hand truck, etc.) designed to carry cylinders.
Never insert an object (for example, wrench, screwdriver, lever bar) into the openings of the lid, since h Doing so may damage the valve and cause leakage.
An adjustable wrench is used to remove the caps that are too tight or rusty. The valve should open slowly and if this is impossible, you should stop using and contact your supplier. Of course, the vessel valve should be closed after each use.
Said container must be kept closed even when it is empty. Never place localized flame or heat directly into any part of the vessel. High temperatures can damage the container and cause the pressure relief device to prematurely break, venting the contents of the container (praxair inc., 2016).
Synthesis
Gaseous hydrogen bromide can be manufactured in the laboratory by bromination of tetralin (1, 2, 3, 4-tetrahydronaphthalene). The disadvantage 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 Referring to Fig. Br 4 + 4 HBr
Hydrogen bromide gas can also be synthesized in the laboratory by the reaction of concentrated sulfuric acid with sodium bromide.
NaBr (s) + H 2 SW 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 SW 4 → Br 2 + SO 2 + 2 H 2 OR
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 [Pt] → 2 HBr
Small-scale anhydrous hydrogen bromide may also be produced by thermolysis of triphenylphosphonium bromide in xylene at reflux.
HBr can be obtained by the red phosphorus method. Firstly, the red phosphorus is added in the water reactor and then, slowly, the bromine under agitation and the reaction of hydrobromic acid and phosphorous acid, by sedimentation, filtration and the obtained distillation will be hydrobromic acid.
P 4 +6 Br 2 +12 H 2 O → 12 HBr + 4 H 3 PO 3
The hydrogen bromide prepared by the above methods can be 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, yielding 2,4,6-tribromophenol and thereby generating More HBr.
This process can also be carried out through copper chips or high temperature 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, 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 flame retardants.
The compound is also used to engrave polysilicon sheets for the manufacture of computer chips (Interscan Corporation, 2017).
Hydrogen bromide is a good solvent for some metal ores 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 HBr gas is used for recording and cleaning for the semiconductor raw material (SHOWA DENKO K.K, s.f.).
The compound is used as an analytical reagent in the determination of sulfur, selenium, bismuth, zinc and iron, for the removal 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-Hydrogen Bromide Monitoring Instrumentation. Retrieved from gasdetection.com.
- Chemical Datasheet. (2016). Retrieved from HYDROGEN BROMIDE, ANHYDROUS: cameochemicals.noaa.gov.
- Egon Wiberg, N.W. (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. (S.F.). 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 K.K. (S.f.). Hydrogen bromide. Retrieved from www.sdk.co.jp.