Boron: Properties, Applications & Lab Uses

Boron is a metalloid element with exceptional chemical versatility, underpinning applications that range from semiconductor doping and high-strength materials to cutting-edge pharmaceutical and catalytic research.

Atomic Number

5

Atomic Weight

10.81 g/mol

CAS Number

7440-42-8

Melting Point

2076 °C (amorphous form varies)

Natural Isotopes

¹⁰B (19.9%) and ¹¹B (80.1%)

Appearance

Dark brown to black powder (amorphous) or black lustrous solid (crystalline)

Chemical Properties and Structure

Boron (symbol B, atomic number 5) is the only metalloid in Group 13 of the periodic table. It exists in two principal allotropic forms: amorphous boron, a dark brown powder, and crystalline boron, a very hard black solid. Crystalline boron is notable for its icosahedral B₁₂ cluster units, which confer exceptional hardness and thermal stability.

Boron has a relatively high melting point (~2076 °C) and is a poor electrical conductor at room temperature, though its conductivity increases significantly at elevated temperatures, a property typical of semiconductors. Its two stable naturally occurring isotopes, ¹⁰B and ¹¹B, are of considerable scientific interest: ¹⁰B has a very high neutron-capture cross-section, making it invaluable in nuclear applications and boron neutron capture therapy (BNCT).

Boron is electron-deficient, forming only three covalent bonds in many of its compounds, which results in a vacant p-orbital. This Lewis acid character makes boron compounds highly reactive toward Lewis bases and underpins a wide array of coordination chemistry applications.

Key Laboratory and Industrial Applications

Boron and its compounds serve a remarkably broad range of purposes in both research and industry:

• Semiconductor Doping: Elemental boron is a p-type dopant widely used in the semiconductor industry to modify the electrical properties of silicon and other materials.
• High-Performance Materials: Boron carbide (B₄C) and boron nitride (BN) are synthesized from elemental boron for use in cutting tools, armor plating, and advanced ceramics due to their exceptional hardness and thermal stability.
• Organic and Medicinal Chemistry: Boronic acids and boronate esters—derived from boron sources—are essential building blocks in Suzuki–Miyaura cross-coupling reactions, a cornerstone of modern pharmaceutical synthesis. Boron-containing compounds also feature prominently in proteasome inhibitor drugs.
• Boron Neutron Capture Therapy (BNCT): The high neutron-capture cross-section of ¹⁰B is exploited in experimental cancer treatment strategies, where boron-labeled compounds are selectively delivered to tumor cells.
• Analytical Chemistry: Boron is used as a reference standard and in the preparation of borate buffers widely employed in gel electrophoresis and chromatography.

Safety, Handling and Storage

When working with elemental boron in the laboratory, adherence to standard chemical safety practices is essential:

• Inhalation Risk: Fine boron powder can be a respiratory irritant. Always work in a well-ventilated area or fume hood and use appropriate respiratory protection (N95 or better) when handling powdered forms.
• Skin and Eye Contact: Boron dust may cause mechanical irritation to skin and eyes. Wear nitrile gloves, safety goggles and a lab coat at all times.
• Fire and Reactivity: Amorphous boron powder is combustible and can ignite under certain conditions. Keep away from open flames and strong oxidizing agents. Store in a cool, dry location away from incompatible materials.
• Disposal: Dispose of boron waste in accordance with local regulations for inorganic chemical waste. Do not pour down the drain without confirming local discharge limits.

Always consult the Safety Data Sheet (SDS) provided with your Aladdin Scientific product before use.

Selecting the Right Boron Reagent for Your Research

Choosing the correct form and purity of boron is critical for reproducible, high-quality research outcomes. Key considerations include:

• Purity Grade: For semiconductor, electronic, or high-sensitivity analytical applications, select high-purity (≥99.9%) elemental boron to minimize trace-metal interference. For synthetic chemistry, standard reagent-grade boron is typically sufficient.
• Physical Form: Amorphous boron powder offers higher surface reactivity and is preferred for chemical synthesis and pyrotechnic applications. Crystalline boron is preferred where structural or electronic precision is required.
• Particle Size: Finer particle sizes increase surface area and reaction rates but require more stringent handling precautions due to increased inhalation risk.
• Isotopic Purity: For BNCT research or neutron-related physics experiments, isotopically enriched ¹⁰B or ¹¹B materials may be required. Standard natural-abundance boron contains approximately 19.9% ¹⁰B and 80.1% ¹¹B.

Aladdin Scientific's Boron (SKU: B105884) offers a reliable, quality-assured source for research and development applications. Contact our technical team for custom purity or particle-size requirements.

Frequently asked questions

What is the difference between amorphous and crystalline boron?

Amorphous boron is a dark brown powder with a disordered atomic structure and higher surface reactivity, making it preferred for chemical synthesis and pyrotechnic applications. Crystalline boron is a very hard, black, lustrous solid with an ordered icosahedral lattice structure, offering superior thermal stability and hardness. The two forms differ in density, hardness and electrical properties.

Why is the ¹⁰B isotope important in medical research?

¹⁰B has an exceptionally high neutron-capture cross-section, meaning it readily absorbs thermal neutrons and undergoes a fission reaction that releases high-energy alpha particles and lithium ions. In boron neutron capture therapy (BNCT), boron-labeled compounds are selectively delivered to tumor cells; irradiation with neutrons then causes localized cell destruction with minimal damage to surrounding healthy tissue.

Can elemental boron be used directly in Suzuki–Miyaura cross-coupling reactions?

Elemental boron itself is not typically used directly as the boron source in Suzuki–Miyaura reactions; these reactions require boronic acids or boronate esters as coupling partners. However, elemental boron serves as a precursor in the synthesis of various organoboron reagents and boron-containing compounds that feed into such transformations.

How should elemental boron powder be stored to maintain its quality?

Elemental boron powder should be stored in a tightly sealed container in a cool, dry, well-ventilated area, away from moisture, open flames and strong oxidizing agents. Prolonged exposure to moisture or air can lead to surface oxidation, which may affect reactivity. Always follow the storage instructions provided in the product SDS.

References

1. Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements, 2nd ed.; Butterworth-Heinemann: Oxford, 1997; Chapter 6.
2. Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed.; Pearson: Harlow, 2018; Chapter 13.
3. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95 (7), 2457–2483. doi:10.1021/cr00039a007
4. Barth, R. F.; Coderre, J. A.; Vicente, M. G. H.; Blue, T. E. Boron Neutron Capture Therapy of Cancer: Current Status and Future Prospects. Clin. Cancer Res. 2005, 11 (11), 3987–4002. doi:10.1158/1078-0432.CCR-05-0035

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.