Synthesis of fluorobenzene

Preparation of fluorobenzene

Preparation of fluorobenzene

Preparation of fluorobenzene

Water (1350 ml) and hydrochloric acid (1650ml; d 1.19) are mixed in a 40-liter pot or in a glass jar (30 x 30 cm) and stirred vigorously whilst cooling in ice-salt. Then a solution of sodium nitrite (1200 g) in water (1500 ml) is prepared, and one-third of the total (2075 g) aniline hydrochloride is added to the hydrochloric acid at 5°. Sodium nitrite solution is added to this solution so that the temperature does not rise above 7°. Further portions of aniline hydrochloride are added, ensuring that solid is always present. All the aniline hydrochloride should have been added by the time that half the sodium nitrite has been added. Complete diazotization requires about all the nitrite (test with starch-iodide paper!). Meanwhile a solution of tetrafluoroboric acid is prepared by portionwise mixing, with stirring, of boric acid (1000 g, 16.2 moles) and 60% hydrogen fluoride (2150 g, 65 moles) in copper, lead, or plastic vessels, the temperature not being allowed to exceed 25° (cooling in ice-water); this solution is then cooled to 0° and allowed to flow into the diazonium solution, cooled to below 0°, at such a rate that the temperature does not exceed 10°. The thick mass is well stirred by a slowly rotating metal or wooden stirrer with large wings and an acid-fast coating or a rubber covering. When all the tetrafluoroboric acid has been added (20-30 min), the solids are filtered off and washed successively with ice-water (about 800 ml), methanol or ethanol (about 800 ml), and ether (900 ml), the mass being sucked as dry as possible on each occasion. The diazonium fluoroborate is spread in a thin layer and left in the air to dry, then placed in a 12-1 flask or divided between two 5-liter flasks. The reaction flask is connected by wide tubes to a wide condenser and thence to a series of three Erlenmeyer flasks standing in a freezing bath and acting as receivers. The exit gases are led directly to a fume cupboard or first through ice-water or sodium hydroxide solution. When the diazonium fluoroborate is warmed externally by a free flame at a position near its surface, decomposition soon sets in; this reaction is allowed to proceed as long as it continues quietly; if it becomes too violent ice-cooling is applied, if it slackens heating is repeated, until finally no more boron trifluoride vapor is evolved on substantial heating. The distillate collected in the receivers is separated from the phenol that has crystallized out. It is then washed several times with 10% sodium hydroxide solution (until the washings are almost colorless) and last with water; the density of fluorobenzene is 1.024 g/mL at 25 °C, so the last portion of sodium hydroxide solution must be very carefully separated, lest a dilute sodium hydroxide solution be obtained of almost this density, making separation from fluorobenzene very difficult. Drying over calcium chloride and fractionation through a column (b.p. 85 °C) give a 50-56% yield (780-870 g) of fluorobenzene, b.p. 84-85°.

G. Balz, G. Schiemann, Ber. Deut. Chem. Ges., 60, 1186 (1927).





InChI Key


Canonical SMILES


MeSH Synonyms


Depositor-Supplied Synonyms

FLUOROBENZENE, 462-06-6, Monofluorobenzene, Phenyl fluoride, Benzene, fluoro-, Fluorbenzol, fluoro-benzene, 4-fluorobenzene, UNII-G3TSZ68K12, CHEBI:5115, fluoranylbenzene, PYLWMHQQBFSUBP-UHFFFAOYSA-N, EINECS 207-321-7, MFCD00000280, NSC 68416, UN2387, AI3-28560, Fluorobenzenes, 1,2,3,4,5-pentadeuterio-6-fluorobenzene, fluoro benzene, p-fluorobenzene, Benzene,fluoro-, 3-fluoro benzene, AC1L1UAQ, WLN: FR, DSSTox_CID_5329, Fluorobenzene [UN2387] [Flammable liquid], F6001_ALDRICH, ACMC-1AH29, DSSTox_RID_77751, DSSTox_GSID_25329, KSC226C4D, 47321_SUPELCO, CHEMBL16070, G3TSZ68K12, DTXSID4025329, 46660_FLUKA, 46662_FLUKA, 51411_FLUKA, ZINC967759, NSC68416, Tox21_201054, ANW-75641, BBL023306, NSC-68416, PC3480, STL268902, ZINC00967759, AKOS000120121, LS-1273, MCULE-7689730731, PF10006, RP18603, TRA0162031, UN 2387, NCGC00091679-01, NCGC00091679-02, NCGC00258607-01, AN-23458, CAS-462-06-6, DA-05689, KB-51886, OR025020, OR272058, ZB015488, KB-287706, F0034, Fluorobenzene [UN2387] [Flammable liquid], FT-0612444, FT-0618548, FT-0626473, FT-0653252, H2656, S0674, V0805, C11272, 72787-EP2269993A1, 72787-EP2305627A1, 72787-EP2309584A1, 72787-EP2377610A2, 72787-EP2377611A2, 90921-EP2272822A1, 90921-EP2305640A2, 189047-EP2371831A1, A827008, I01-5035, S01-0459, I01-10184, F0001-1250, InChI=1/C6H5F/c7-6-4-2-1-3-5-6/h1-5

Removed Synonyms

ACETONITRILE, P-FLUOROTOLUENE, MolPort-000-155-451, CID10008, RTR-015149, D005464, 352-32-9, 1423-10-5

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