by Properties and Structure of Silicon tetrabromide
Silicon Tetrachloride, also known as silicon tetrabromide, is an inorganic compound with the chemical formula of SiCl4. It is a colorless crystalline solid that melts at -13.5°C and boils at 58°C. In the gaseous and liquid states, silicon tetrabromide is highly moisture-sensitive and hydrolyzes readily to form hydrogen chloride gas and polymeric silica according to the reaction:
SiCl4 + 2H2O → SiO2 + 4HCl
This hydrolysis reaction makes Silicon Tetrabromide dangerous to handle without appropriate safety precautions. The silicon-chlorine bond length in crystalline solid is 2.01Å while the silicon-chlorine-chlorine bond angle is 108.5°, resulting in a tetrahedral molecular structure around the central silicon atom.
Uses and Production of Silicon Tetrachloride
Silicon tetrabromide finds a variety of industrial uses mainly as an intermediate in the production of other silicon compounds, fibers and ceramics. It is used as a chlorinating agent in organic synthesis to introduce chlorine into organic compounds. Being colorless and inorganic, silicon tetrabromide is used as a chlorine transfer reagent and levelling agent in the production of silicone polymers, elastomers and sealants.
The majority of silicon tetrabromide is produced in a direct combination reaction between chunks of metallic silicon and chlorine gas at 1000-1200°C according to the reaction:
Si (s) + 2Cl2 (g) → SiCl4 (g)
This single step reaction produces anhydrous silicon tetrabromide in high yields without the need for complicated purification steps. An alternate production route involves the reaction of sand (silicon dioxide) with coke and chlorine gas at higher temperatures of around 1400°C. This carbothermic reduction produces contaminants like carbon and needs further processing for pure silicon tetrabromide.
Purification and Refinement of Silicon tetrabromide
Crude silicon tetrabromide obtained from production requires careful purification and refinement before being used in further chemical reactions and applications. Traces of impurities like moisture, carbon, metals need to be removed to obtain high purity compound.
Some common purification techniques include:
– Vacuum distillation: Repeated vacuum distillation exploits the difference in boiling points of silicon tetrabromide and impurities for purification.
– Combustion of carbon: Passing through a heated combustion tube burns any carbon impurities to carbon dioxide and monoxide.
– Scrubbing with alcohol: Bubbling through isopropyl alcohol scrubs off any hydrolyzable impurities like HCl.
– Drying through mol sieves: Drying agent like silica gel traps and removes trace moisture through physical adsorption.
– Fractional vacuum distillation: High vacuum distillation at sub-atmospheric pressures has a stripping effect to fractionally recover ultra-pure grade material.
Uses of Purified Silicon Tetrachloride
Purified silicon tetrabromide finds extensive usage in electronics, aerospace and material industries:
– CVD/ALD Precursor: It acts as an important precursor for chemical vapor deposition (CVD) and atomic layer deposition (ALD) of thin silicon, silicon nitride and silicon oxide layers on wafers in semiconductor industry.
– Silicone Production: Reaction with sodium or magnesium produces intermediates like dichlorosilane for large scale production of silicones, elastomers and sealants.
– Fibers and ceramics: Used for production of silica fibers and silicon nitride/carbide ceramics known for their high strength, heat resistance and other properties.
– Hydrofluoric Acid Manufacture: Anti-caking agent and reactant for production of anhydrous hydrofluoric acid used in stainless steel pickling.
– Chlorosilane Chemistry: Versatile building block and starting reagent for synthesized organosilicon compounds due to presence of reactive chlorine.
Safety Considerations with Silicon tetrabromide
Being strongly hydrolyzing and moisture sensitive, handling of liquid or gaseous silicon tetrabromide requires strict safety precautions:
– Use in well-ventilated enclosure and wear appropriate gloves, goggles and protective clothing.
– Inspect all lines and joints carefully for any moisture ingress that can cause hazardous HCl corrosion over time.
– In case of exposure, flush with water and seek immediate medical attention. HCl gas can cause damage to eyes, skin and respiratory tract.
– For storage, use moisture-proof containers and store in ventilated areas away from incompatible materials like oxidizers or bases that can undergo exothermic reactions.
In conclusion, silicon tetrachloride ide is a versatile industrial chemical intermediate used across many industries due to ready availability from relatively simple precursor reactions and transformations. However, its hydrolytic nature demands proper safety handling to realize its useful applications.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
About Author - Money Singh
Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc. LinkedIn Profile
