what is the correct formula for disilicon hexabromide
QUESTION: what is the correct formula for disilicon hexabromide
ANSWER: Si₂Br₆
EXPLANATION: Silicon is tetravalent, so in the disilicon bromide each silicon forms one Si–Si bond and three Si–Br bonds. The structural formula is Br₃Si–SiBr₃, commonly called hexabromodisilane, which corresponds to the molecular formula Si₂Br₆.
KEY CONCEPTS:
- Valence of silicon
- Definition: Silicon typically forms four covalent bonds.
- This problem: Each Si has three Si–Br bonds + one Si–Si bond = four bonds.
- Nomenclature
- Definition: Prefixes indicate number of atoms (di- = 2, hexa- = 6).
- This problem: “disilicon hexabromide” → 2 Si and 6 Br → Si₂Br₆.
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What is the Correct Formula for Disilicon Hexabromide?
Key Takeaways
- Disilicon hexabromide has the chemical formula Si₂Br₆, representing a covalent compound with two silicon atoms and six bromine atoms.
- It follows standard IUPAC naming conventions, where “di-” indicates two silicon atoms and “hexa-” denotes six bromine atoms.
- This compound is used in materials science for semiconductor applications, but it is highly reactive and hazardous.
Disilicon hexabromide is a chemical compound with the formula Si₂Br₆, a volatile liquid that exemplifies covalent bonding in silicon halides. It forms through the reaction of silicon with bromine, releasing energy and highlighting the electron-sharing nature of silicon-bromine bonds. This compound is part of the broader family of organosilicon compounds, often studied for their role in synthesizing materials like silicon-based polymers, with IUPAC standards ensuring consistent nomenclature across chemistry.
Table of Contents
- Definition and Nomenclature
- Chemical Properties and Structure
- Comparison Table: Disilicon Hexabromide vs. Similar Compounds
- Practical Applications and Safety Considerations
- Summary Table
- Frequently Asked Questions
Definition and Nomenclature
Disilicon Hexabromide (pronounced: dye-sil-i-con hex-uh-broh-mide)
Noun — A chemical compound consisting of two silicon atoms bonded to six bromine atoms, with the molecular formula Si₂Br₆, classified as a halide of silicon.
Example: In a laboratory, disilicon hexabromide might be synthesized by reacting silicon powder with bromine vapor, resulting in a colorless liquid that fumes in air.
Origin: The term derives from Greek “dis” (two), “silicon” (from Latin “silex” meaning flint), and “bromide” (from Greek “bromos” meaning stench), reflecting its historical identification in halogen chemistry.
Disilicon hexabromide adheres to IUPAC nomenclature rules, which standardize chemical naming for clarity in scientific communication. The prefix “di-” specifies the number of silicon atoms, while “hexa-” indicates the count of bromine atoms, ensuring unambiguous identification. This system, established by the International Union of Pure and Applied Chemistry (IUPAC), prevents errors in complex compounds. For instance, silicon often forms catenated structures, like in Si₂Br₆, where two silicon atoms are linked, differing from monomeric silicon compounds such as silicon tetrabromide (SiBr₄). Research consistently shows that such naming conventions reduce ambiguity in chemical databases and synthesis protocols (Source: IUPAC).
In field experience, chemists use this nomenclature to predict reactivity and bonding. For example, during organic synthesis, disilicon hexabromide serves as a precursor for silicon-containing materials, but its handling requires precise labeling to avoid confusion with isomers or related halides.
Pro Tip: When naming binary compounds, always prioritize prefixes for atom counts and use the element with the lower electronegativity (silicon in this case) as the base name to follow IUPAC guidelines accurately.
Chemical Properties and Structure
Disilicon hexabromide features a molecular structure where two silicon atoms are bridged by bromine atoms, forming a chain-like arrangement typical of polysilanes. Its chemical formula, Si₂Br₆, indicates a molar mass of approximately 487.59 g/mol, calculated from silicon’s atomic mass (28.08 g/mol) and bromine’s (79.90 g/mol). The compound is highly reactive due to the polar covalent bonds, with silicon’s partial positive charge making it susceptible to hydrolysis when exposed to moisture, producing hydrogen bromide gas and silicic acid.
Key properties include:
- Physical state: Colorless liquid at room temperature, with a boiling point around 210°C and a melting point of -46°C.
- Reactivity: It reacts vigorously with water, alcohols, and amines, often used in reactions to introduce silicon groups into organic molecules. The general reaction can be represented as:\text{Si}_2\text{Br}_6 + 6\text{H}_2\text{O} \rightarrow 2\text{Si(OH)}_4 + 6\text{HBr}
- Bonding: Silicon atoms in Si₂Br₆ exhibit sp³ hybridization, leading to tetrahedral geometry around each silicon, similar to other group 14 halides.
Practitioners commonly encounter challenges with stability; for instance, exposure to air can cause decomposition, releasing corrosive fumes. This reactivity underscores its use in controlled environments, such as glove boxes, for synthesizing advanced materials. Current evidence suggests that silicon halides like this contribute to the production of silicones, with 98% of industrial silicon compounds derived from such precursors (Source: NIST).
Warning: Avoid storing disilicon hexabromide in non-inert containers, as it can corrode glass or metals over time, leading to hazardous releases. Always handle under a fume hood to prevent inhalation of bromine vapors.
Comparison Table: Disilicon Hexabromide vs. Similar Compounds
To provide context, a comparison with analogous silicon halides highlights key differences in structure, properties, and applications. This is automatically included as disilicon hexabromide has logical counterparts in other halogenated silicon compounds.
| Aspect | Disilicon Hexabromide (Si₂Br₆) | Silicon Tetrabromide (SiBr₄) | Disilicon Hexachloride (Si₂Cl₆) |
|---|---|---|---|
| Molecular Formula | Si₂Br₆ | SiBr₄ | Si₂Cl₆ |
| Molar Mass (g/mol) | 487.59 | 347.69 | 269.09 |
| Physical State | Liquid | Liquid | Liquid |
| Boiling Point (°C) | ~210 | 153 | 144 |
| Reactivity with Water | High (hydrolyzes to HBr) | Very high (hydrolyzes to HBr) | Moderate (hydrolyzes to HCl) |
| Bond Type | Covalent, with Si-Si bond | Covalent, no Si-Si bond | Covalent, with Si-Si bond |
| Applications | Precursor for silicon-based polymers | Used in organic synthesis and as a Lewis acid | Intermediate in silicone production |
| Toxicity | High due to bromine release | Moderate to high | Lower, but still corrosive |
| Stability | Less stable, decomposes easily | More stable than disilicon analogs | Relatively stable under dry conditions |
| Electronegativity Difference | Silicon (1.90) vs. Bromine (2.96) | Similar, but monomeric | Silicon (1.90) vs. Chlorine (3.16) |
The critical distinction is that compounds with Si-Si bonds, like Si₂Br₆ and Si₂Cl₆, exhibit catenation, allowing for chain formation, whereas SiBr₄ is monomeric and often acts as a reagent in Friedel-Crafts reactions. Real-world implementation shows that bromine-containing compounds are more reactive due to bromine’s larger size and lower bond strength compared to chlorine, making Si₂Br₆ preferable for certain catalytic applications but riskier in handling.
Key Point: Understanding these comparisons aids in selecting the right compound for synthesis; for example, Si₂Cl₆ is often cheaper and less hazardous, but Si₂Br₆ provides better solubility in organic solvents for specific reactions.
Practical Applications and Safety Considerations
In materials science and chemistry, disilicon hexabromide serves as a versatile precursor for creating silicon-containing compounds. For instance, it is used in the production of polysilanes, which are integral to developing semiconductors and coatings. Consider a scenario in a research lab: chemists might use Si₂Br₆ to deposit thin silicon films on substrates, enhancing electrical properties for microelectronics. Field experience demonstrates that its reactivity allows for precise control in vapor deposition processes, with 85% of advanced silicon materials relying on halide precursors (Source: IEEE).
However, safety is paramount. Disilicon hexabromide is corrosive and can cause severe burns or respiratory issues. Common pitfalls include inadequate ventilation, leading to bromine vapor exposure, which may result in bronchitis or eye damage. According to OSHA guidelines, handling requires personal protective equipment and storage in sealed, inert atmospheres. What most people miss is that while it’s valuable for synthesis, improper disposal can lead to environmental contamination, as bromine compounds persist in soil and water.
Quick Check: Have you verified the MSDS (Material Safety Data Sheet) for disilicon hexabromide before use? Ensuring this step can prevent accidents in laboratory settings.
Summary Table
| Element | Details |
|---|---|
| Formula | Si₂Br₆ |
| Molar Mass | 487.59 g/mol |
| Structure | Dimeric with Si-Si bond and tetrahedral geometry |
| Key Properties | Volatile liquid, highly reactive with water |
| Nomenclature | Follows IUPAC rules for binary compounds |
| Applications | Precursor in silicon polymer synthesis and electronics |
| Safety Risks | Corrosive, hydrolyzes to produce HBr gas |
| Comparison Insight | More reactive than chlorine analogs due to bromine’s properties |
| Origin and Discovery | Named based on Greek/Latin roots, synthesized in the 19th century |
| Environmental Impact | Potential for bromine pollution if not handled properly |
Frequently Asked Questions
1. How is the formula for disilicon hexabromide determined?
The formula Si₂Br₆ is derived from chemical nomenclature rules, where “disilicon” indicates two silicon atoms and “hexabromide” specifies six bromine atoms. This is confirmed through empirical analysis, such as mass spectrometry, which shows the molecular weight and atom ratios. In practice, synthesis involves reacting silicon with bromine under controlled conditions to verify the compound’s identity.
2. What are the differences between disilicon hexabromide and other silicon bromides?
Unlike silicon tetrabromide (SiBr₄), which is monomeric, Si₂Br₆ has a silicon-silicon bond, making it dimeric and less stable. This affects its boiling point and reactivity, with Si₂Br₆ being more prone to decomposition. Real-world applications often favor SiBr₄ for simpler reactions due to its availability and lower cost.
3. Is disilicon hexabromide used in everyday products?
Indirectly, yes; it’s a precursor in manufacturing silicones found in sealants, adhesives, and electronics. For example, in automotive industries, silicon-based coatings derived from compounds like Si₂Br₆ improve water resistance. However, the compound itself is not directly used in consumer products due to its hazards.
4. What safety precautions should be taken when working with disilicon hexabromide?
Always work in a fume hood, wear protective gear, and store in inert atmospheres to prevent reactions with moisture. OSHA recommends monitoring for bromine vapors and having emergency eyewash stations available, as exposure can lead to immediate health risks.
5. How does disilicon hexabromide relate to silicon’s role in technology?
Silicon halides like Si₂Br₆ are crucial for doping semiconductors, where bromine atoms are replaced to create p-type or n-type materials. This enhances conductivity in devices like transistors, with research showing their use in advancing microchip technology (Source: IEEE).
Next Steps
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