Boron trifluoride
[CAS# 7637-07-2]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Metal halides and halides >> Metal fluorides and salts
• Name: Boron trifluoride
• Synonyms: trifluoroborane
• Molecular Formula: BF₃
• Molecular Weight: 67.80
• CAS Registry Number: 7637-07-2
• EC Number: 231-569-5
• SMILES: B(F)(F)F

Properties

• Density: 1.0$+/-$0.1 g/cm³ Calc.^*, 3.076 g/mL (Expl.)
• Melting point: -127 $degree$C (Expl.)
• Boiling point: -100.0 $degree$C 760 mmHg (Calc.)^*, -100 $degree$C (Expl.)
• Flash point: 4 $degree$C (Expl.)
• Solubility: 105-107 g/100g (Expl.)
• Index of refraction: 1.138 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS04;GHS05;GHS06 Danger
• Risk Statements: H314-H330
• Safety Statements: P260-P264-P271-P280-P284-P301+P330+P331-P302+P361+P354-P304+P340-P305+P354+P338-P316-P320-P321-P363-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1A	H314
Acute toxicity	Acute Tox.	2	H330
Gases under pressure (compressed)	Press. Gas (Comp.)		H280
Serious eye damage	Eye Dam.	1	H318
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - single exposure	STOT SE	3	H335
Gases under pressure (liquid)	Press. Gas (Liq.)		H280
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H312
Skin corrosion	Skin Corr.	1B	H314
Specific target organ toxicity - single exposure	STOT SE	2	H371
Flammable liquids	Flam. Liq.	3	H226
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Acute toxicity	Acute Tox.	2	H300
Acute toxicity	Acute Tox.	4	H332

• Transport Information: UN 1008

Discovery and Applications

Boron trifluoride is a colorless, toxic, and corrosive gas with the chemical formula BF₃. It consists of a boron atom covalently bonded to three fluorine atoms in a trigonal planar geometry, giving the molecule a strong electron-deficient character. Boron trifluoride was first prepared in the early 19th century by the reaction of boron compounds with hydrofluoric acid and has since been widely used as a Lewis acid catalyst in chemical synthesis and industrial processes.

The molecular structure of BF₃ features sp² hybridization of the central boron atom, resulting in a planar triangular configuration with bond angles of approximately 120°. The electron deficiency at boron allows the molecule to readily accept electron pairs, making it a strong Lewis acid. Its volatility and reactivity require careful handling, as it reacts with water to form boric acid and hydrogen fluoride, which are highly corrosive.

Boron trifluoride is extensively used as a catalyst in organic chemistry, particularly in reactions requiring electron pair acceptance. It catalyzes Friedel–Crafts alkylation and acylation reactions, polymerization of olefins, and isomerization of hydrocarbons. In these processes, BF₃ forms adducts with nucleophiles, facilitating the generation of carbocations or activating reactants for further chemical transformations.

In addition to its catalytic role, BF₃ is used in the production of organoboron compounds, which serve as intermediates in pharmaceuticals, agrochemicals, and specialty materials. Its ability to form stable complexes with diols, amines, and ethers allows for controlled synthesis of boron-containing molecules with applications in chemical research and industrial manufacturing.

Boron trifluoride is also employed in analytical chemistry as a complexing agent and in the preparation of boron-doped materials. In the semiconductor industry, it is used to introduce boron into silicon wafers, enabling controlled p-type doping for electronic devices. Its reactivity with moisture and nucleophiles requires handling under dry, inert conditions, often using specialized gas delivery systems or complexed forms, such as BF₃·etherate, which provides safer and easier handling.

Overall, boron trifluoride is a highly reactive, electron-deficient gas with significant utility as a Lewis acid catalyst, reagent for organoboron synthesis, and dopant in semiconductor fabrication. Its trigonal planar structure and strong affinity for electron pairs make it an essential compound in organic, inorganic, and materials chemistry.

References

2025. Mechanism of dry eye syndrome improvement by Tetraselmis chuii: Anti-inflammatory effects and ocular mucous membrane restoration. Journal of Applied Phycology.
DOI: 10.1007/s10811-025-03598-7

2025. Silica-loaded perchloric acid as a catalyst for terpene phenol resins. Iranian Polymer Journal.
DOI: 10.1007/s13726-025-01526-7

2025. Spontaneous granulation of tricaprin and trilaurin medium-chain triacylglycerols with added medium- and long-chain species. npj Science of Food.
DOI: 10.1038/s41538-025-00511-x