Synthesis of boron trifluoride

Preparation of boron trifluoride

Boron trifluoride is prepared by reacting  ammonium fluoroborate (or any soluble fluoroborate e.g. potassium fluoroborate, sodium fluoroborate in the place of the ammonium salt).

Preparation of boron trifluoride

Preparation of boron trifluoride

Boron trifluoride is prepared in the apparatus shown bellow.

A glass apparatus for the preparation of boron trifluoride

A glass apparatus for the preparation of boron trifluoride

Since boron trifluoride attacks cork less than it does rubber, cork stoppers should be used and rubber connections avoided as far as possible. Where a very pure product is desired, an all-glass apparatus must be used. Ground joints may be lubricated with a paraffin-vaseline mixture. The generating flask A has a volume of 500 ml. B is empty and used as a trap; C contains some 30 ml of sulfuric acid saturated with boric acid, to absorb hydrogen fluoride from the gas stream. In A, 50 g of ammonium fluoroborate (prepared from 65 grams (1.15 moles) of ammonium fluoroborate, with 30 grams (0.5 mole) of boric acid), are well mixed with 6 g of finely powdered boric oxide. In D, 30 ml of diethyl ether are placed, and cooled the tube in ice. The escaping gas passing out of D is sucked away by the draft or to be absorbed in caustic soda. When all is ready, 40 ml of concentrated sulfuric acid are poured into flask A . A vigorous reaction occurs, which, however, soon slackens and must be maintained by heating. The reaction is going steadily but not too fast. Some of the boron trifluoride is absorbed by the ether in D, forming a viscous solution of the addition compound Et2O · BF3. If the D tube is filled water the reaction between boron trifluoride and water occurs yielding viscous liquids BF3 · 2H20 and BF3 · H2O.

Inorganic preparations: a laboratory manual, by H. F. Walton, 101-102, 1948.

Boron trifluoride is also prepared by treating boron anhydride with hydrogen fluoride.

Preparation of boron trifluoride

Preparation of boron trifluoride

Hydrofluoric acid gas reacts with boron anhydride, forming boron trifluoride. Hydrofluoric acid gas is generated in the presence of boric anhydride by heating a mixture of 24 g of powdered calcium fluoride, 10 g of powdered boric anhydride, and 20 g of concentrated sulphuric acid in a Erlenmeyer flask.A one-holed stopper, carrying a glass elbow, is inserted in the neck of the flask and two dry cylinders are arranged as shown below.

A glass apparatus for the preparation of boron trifluoride

A glass apparatus for the preparation of boron trifluoride

Provision is made for conducting the escaping gas into a flue. The flask is then gently heated, and the boron trifluoride evolved soon expels the air from the flask and the two cylinders, and fumes strongly in the air as it escapes into the flue.

Chemical lecture experiments, by F. G. Benedict, 279, 1916.





InChI Key


Canonical SMILES


MeSH Synonyms

boron trifluoride

Depositor-Supplied Synonyms

Trifluoroborane, BORON TRIFLUORIDE, Boron fluoride, Borane, trifluoro-, Trifluoroboron, Anca 1040, Boron fluoride (BF3), 7637-07-2, Fluorure de bore, Fluorure de bore [French], Borontrifluoride, trifluoro Boron, HSDB 325, CHEBI:33093, WTEOIRVLGSZEPR-UHFFFAOYSA-N, EINECS 231-569-5, UN1008, 109704-87-2, BF3, trifluoroborate, Bortrifluorid, trifluoridoboron, boron trifluride, Trifluoro-borane, boron triflouride, (11B)Boron trifluoride, AC1L1MCF, BF3 – Butanol solution, Borane-11B, trifluoro-, UNII-7JGD48PX8P, B1252_ALDRICH, 7JGD48PX8P, Boron trifluoride, compressed, 15712_ALDRICH, B1252_SIGMA, Leecure B series (Salt/Mix), 295027_ALDRICH, 463086_ALDRICH, CHEMBL2220705, 15712_FLUKA, 15715_FLUKA, 15716_FLUKA, 15718_FLUKA, 83253_FLUKA, CTK2H7573, MolPort-001-771-920, [BF3], InChI=1/BF3/c2-1(3), Boron Trifluoride – Butanol Reagent, Bortrifluoride – 1-butanol solution, EINECS 243-946-1, Boron Trifluoride – Methanol Reagent, Boron Trifluoride – Propanol Reagent, Boron trifluoride (14% in methanol), Boron trifluoride 1-propanol solution, AKOS015916106, PC10708, RP17885, TRA0007151, UN 1008, AN-21804, IN000199, IN012506, KB-48440, LS-44986, FT-0623188, FT-0694035, Boron Trifluoride – Isopropyl Alcohol Reagent, 3B4-1902, Boron trifluoride, compressed [UN1008] [Poison gas], I14-52398, Boron trifluoride, compressed [UN1008] [Poison gas], 155123-44-7, 15875-25-9, 16045-88-8, 353-41-3, 372-85-0, 692-39-7

Removed Synonyms

CID6356, Boron trifluoride-methanol solution, X0034, X0035, X0036, X0037, X0040, 20654-88-0, 373-57-9, 676-65-3, 762-48-1, 98223-57-5

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