Phosphorus tribromide (PBr3) is a compound consisting of one phosphorus atom and three bromine atoms. It is used as a reagent in various chemical reactions, particularly in the synthesis of organic compounds.
| IUPAC Name | Phosphorus Tribromide |
| Molecular Formula | PBr3 |
| CAS Number | 7789-60-8 |
| Synonyms | Phosphorus(III) bromide, Bromophosphorous bromide, Tribromophosphine |
| InChI | InChI=1S/Br3P/c1-4(2)3 |
Phosphorus Tribromide Properties
Phosphorus Tribromide Formula
The formula of phosphorus(III) bromide is PBr3. It consists of one phosphorus atom and three bromine atoms. This compound is formed when phosphorus reacts with bromine. The formula accurately represents the composition of the compound.
Phosphorus Tribromide Molar Mass
The molar mass of phosphorus(III) bromide can be calculated by adding the atomic masses of its constituent elements. Phosphorus has an atomic mass of approximately 31.0 grams per mole, while bromine has an atomic mass of around 79.9 grams per mole. Adding three times the atomic mass of bromine to the atomic mass of phosphorus gives us the molar mass of phosphorus(III) bromide, which is approximately 270.7 grams per mole.
Phosphorus Tribromide Boiling Point
phosphorus(III) bromide has a boiling point of around 173 degrees Celsius. This means that at temperatures above this point, the compound will undergo a phase change from a liquid to a gas. The boiling point is an important characteristic that helps determine the conditions under which the compound can be used or purified.
Phosphorus Tribromide Melting Point
The melting point of phosphorus(III) bromide is approximately -41 degrees Celsius. This temperature signifies the point at which the compound transitions from a solid to a liquid state. Knowing the melting point is crucial for handling and manipulating the compound in various chemical processes.
Phosphorus Tribromide Density g/mL
The density of phosphorus(III) bromide is about 2.85 grams per milliliter (g/mL). Density measures the mass of a substance per unit volume. With its relatively high density, phosphorus(III) bromide is denser than many other common liquids, indicating that it is relatively heavy for its volume.
Phosphorus Tribromide Molecular Weight
The molecular weight of phosphorus(III) bromide is approximately 270.7 grams per mole. This value is calculated by summing up the atomic masses of all the atoms in the compound, based on the molecular formula PBr3. The molecular weight is useful in various calculations, including determining the amount of substance present in a given mass.
Phosphorus Tribromide Structure
phosphorus(III) bromide has a pyramidal molecular structure. It consists of a central phosphorus atom bonded to three bromine atoms. The arrangement gives the molecule a trigonal pyramidal shape, with the phosphorus atom at the apex and the bromine atoms at the base. This structure is important for understanding the compound’s reactivity and behavior in chemical reactions.
Phosphorus Tribromide Solubility
phosphorus(III) bromide is sparingly soluble in water. It reacts with water to produce hydrobromic acid and phosphorous acid. However, it is soluble in organic solvents such as benzene and carbon tetrachloride. Solubility determines the extent to which a compound can dissolve in a particular solvent, which has implications for its applications and handling in various processes.
| Appearance | Colorless liquid |
| Specific Gravity | 2.85 g/mL |
| Color | Colorless |
| Odor | Pungent |
| Molar Mass | 270.7 g/mol |
| Density | 2.85 g/mL |
| Melting Point | -41 °C |
| Boiling Point | 173 °C |
| Flash Point | Not available |
| Water Solubility | Reacts |
| Solubility | Soluble in organic solvents such as benzene and carbon tetrachloride |
| Vapor Pressure | Not available |
| Vapor Density | Not available |
| pKa | Not available |
| pH | Not available |
Phosphorus Tribromide Safety and Hazards
phosphorus(III) bromide poses certain safety hazards and should be handled with caution. It is corrosive and can cause severe burns upon contact with the skin, eyes, or respiratory system. Direct inhalation or ingestion of this compound can result in respiratory and gastrointestinal irritation. It reacts violently with water, releasing toxic fumes and generating heat. Proper ventilation and personal protective equipment, such as gloves and goggles, should be used when working with phosphorus(III) bromide. Additionally, it should be stored away from incompatible substances to prevent potential reactions. Overall, strict adherence to safety protocols and knowledge of the hazards associated with this compound are essential for safe handling.
| Hazard Symbols | Corrosive |
| Safety Description | Handle with caution. Avoid contact with skin, eyes, and respiratory system. Use proper ventilation and personal protective equipment. Store away from incompatible substances. |
| UN IDs | UN1805 |
| HS Code | 2812.90.90 |
| Hazard Class | 8 (Corrosive) |
| Packing Group | II |
| Toxicity | Toxic by inhalation and ingestion. Can cause severe burns and irritation. |
Phosphorus Tribromide Synthesis Methods
In one common method of synthesizing phosphorus(III) bromide, the reaction vessel combines elemental phosphorus and bromine directly, typically under controlled conditions. The reaction proceeds with the transfer of bromine atoms to the phosphorus atoms, resulting in the formation of phosphorus(III) bromide.
Another method involves the reaction between phosphorus trichloride (PCl3) and hydrogen bromide (HBr). In this approach, phosphorus trichloride is first reacted with hydrogen bromide gas, producing phosphorus(III) bromide and hydrogen chloride gas as byproducts. This method offers an alternative route to obtain phosphorus(III) bromide.
In the “red phosphorus method,” one combines red phosphorus with bromine or hydrobromic acid and carries out the reaction under controlled conditions. The red phosphorus serves as a source of phosphorus, reacting with the bromine or hydrobromic acid to yield phosphorus(III) bromide.
These synthesis methods provide pathways for the production of phosphorus(III) bromide, each with its own advantages and considerations. The choice of method depends on factors such as the availability of reagents, desired yield, and specific reaction conditions. It is important to conduct these syntheses in a well-equipped laboratory, adhering to safety protocols and handling procedures for the involved chemicals.
Phosphorus Tribromide Uses
phosphorus(III) bromide finds various applications due to its reactivity and unique properties. Here are some of its uses:
- Organic synthesis: Chemists widely employ phosphorus(III) bromide as a reagent in organic synthesis to convert alcohols into alkyl bromides, a key step in synthesizing numerous organic compounds.
- Pharmaceutical Industry: The production of pharmaceuticals heavily depends on phosphorus(III) bromide to synthesize various drug intermediates and active pharmaceutical ingredients (APIs).
- Flame retardants: Manufacturers utilize phosphorus(III) bromide in the production of flame retardants, enhancing the fire resistance properties of certain polymers for use in industries like electronics and textiles.
- Chemical manufacturing: phosphorus(III) bromide serves as a valuable intermediate in producing other chemicals, including phosphorus compounds such as phosphoric acid derivatives, phosphonates, and phosphates.
- Herbicides and Pesticides: The synthesis of specific active ingredients used in herbicides and pesticides utilizes phosphorus(III) bromide to effectively control weeds, pests, and diseases in agriculture.
- Laboratory research: In laboratory settings, researchers commonly use phosphorus(III) bromide as a reagent in various experiments and reactions, particularly those involving bromination and manipulating organic compounds.
- Chemical analysis: phosphorus(III) bromide finds application in chemical analysis techniques, allowing for the determination of the presence of specific functional groups in organic compounds through bromine substitution reactions.
These diverse uses highlight the importance of phosphorus(III) bromide in organic synthesis, pharmaceuticals, flame retardants, chemical manufacturing, agriculture, laboratory research, and chemical analysis. Its reactivity and versatility make it a valuable compound in various industries and scientific disciplines.
Questions:
Q: Why is AlBr3 called aluminum bromide while PBr3 is phosphorus tribromide?
A: The naming convention for compounds involving metals typically uses the metal’s elemental name followed by the nonmetal’s name, while in the case of PBr3, phosphorus is specified to indicate the presence of a central phosphorus atom.
Q: What word or two-word phrase best describes the shape of phosphorus tribromide?
A: The shape of phosphorus(III) bromide is best described as trigonal pyramidal.
Q: How many valence electrons are in the phosphorus tribromide molecule, PBr3?
A: Phosphorus(III) bromide (PBr3) has 26 valence electrons.
Q: Is phosphorus tribromide ionic or covalent?
A: Phosphorus(III) bromide (PBr3) is a covalent compound.
Q: What is the chemical formula for phosphorus tribromide?
A: The chemical formula for phosphorus(III) bromide is PBr3.
Q: Lewis structure for phosphorus tribromide, PBr3?
A: The Lewis structure for PBr3 shows phosphorus as the central atom with three bonded bromine atoms around it, each connected by a single bond.
Q: Is PBr3 an inversion?
A: No, phosphorus(III) bromide (PBr3) does not exhibit inversion.
Q: Is PBr3 an electrophile?
A: Yes, PBr3 can act as an electrophile in certain reactions, where it accepts electrons.
Q: What is the molecular geometry of PBr3?
A: The molecular geometry of PBr3 is trigonal pyramidal.
Q: Is PBr3 polar or nonpolar?
A: PBr3 is a polar molecule due to the uneven distribution of electron density caused by the presence of polar P-Br bonds.
Q: How many moles of PBr3 contain 3.68 × 10^25 bromine atoms?
A: To determine the number of moles, we need the molar mass of PBr3, then divide the given number of bromine atoms by Avogadro’s number.
Q: What is the correct name for PBr3?
A: The correct name for PBr3 is phosphorus(III) bromide.
Q: Is PBr3 polar?
A: Yes, PBr3 is a polar molecule due to the presence of polar bonds and an uneven distribution of electron density.