Synthesis of benzophenone (diphenyl ketone; benzoylbenzene)

Preparation of benzophenone

Preparation of benzophenone from o-benzoylbenzoic

Preparation of benzophenone (diphenyl ketone; benzoylbenzene)

Preparation of benzophenone (diphenyl ketone; benzoylbenzene)

Prior the synthesis o-benzoylbenzoic acid monohydrate should be dehydrated. 24.4 grams of o-benzoylbenzoic acid monohydrate are placed in a distilling flask fitted with to the suction pump. The flask is heated over a free flame (no gauze) with shaking until the solid melts and the water is expelled. Then the process is finished in few minutes. When the dehytratation process is finished the tube leading to the suction pump is disconnected, and anhydrous o-benzoylbenzoic acid  is treated with 2 grams of the copper salt of o-benzoylbenzoic acid. The flask is stoppered with the outlet tube, which is and connected by means of a rubber tubing to a glass tube resting in a graduate in which there is just enough water to seal the tube, so that the evolution of carbon dioxide can be followed. The flask is heated with a small free flame by reaching the temperature of the liquid to 265° C. The temperature is maintained as close to this as possible throughout the reaction. A steady, vigorous evolution of gas starts and in 20-25 minutes metallic copper separates from the clear solution. The reaction is finished when the abolition of carbon dioxide ceases. The the residue is distilled over a free flame and using an air condenser. The boiling point of benzophenone is 306° C, which condensates as colorless, light or dark yellow oil (which later becomes crystalline mass, if not the crystallization is induced by rubbing).  Benzophenone is purified by crystallization from ligroin (b.p. 60-90° C) yielding 13-16 grams, which melts at 47-48° C.

Copper salt of o-benzoylbenzoic acid is prepared as follows:

24.4 grams of o-benzoylbenzoic acid monohydrate and 5.3 grams of anhydrous sodium carbonate are dissolved in 300 ml of water by boiling, then cooled to 50° C by the addition of ice. The cooled solution is treated  12.5 grams of copper sulfate dissolved in 25 ml of water. The voluminous blue-green precipitate which forms is a copper salt of o-benzoylbenzoic acid monohydrate, which is dehydrated by heating and stirring the suspension until this changes to the granular, anhydrous salt. The salt is collected by filtration, washed with small amount of water and dried at 100° C; yield, 24-25 g.

Instead of 2 grams of copper salt of o-benzoylbenzoic acid as a catalyst, 0.3 grams of copper powder or 0.5 grams of basic copper carbonate could be used. In the first case the flask should be shaken during heating until the metal is dissolved. Copper carbonate should be added carefully and the mixture shaken and gently heated until the neutralization reaction subsides and the water formed is expelled.

Experiments in Organic Chemistry, L. F. Fieser, 199-201, 1941

Preparation of benzophenone from calcium benzoate

Preparation of benzophenone from calcium benzoate

10 g of benzoic acid are heated to boiling with 25 g (excess) of calcium hydroxide and ten times the weight of water, until the acid is completely dissolved and the liquid reacts alkaline. It is then filtered hot from the excess of calcium hydroxide. On cooling most of the calcium benzoate separates out from the filtrate in white needles. The remainder is obtained on evaporating the mother liquor. The salt is filtered and completely dried in metal dishes over a free flame. The mass is now introduced into a metal retort (made of iron or copper), which is connected with a long condenser tube. The retort must not be filled more than two-thirds full. It is heated over a powerful gas burner, so that the dry distillation of the salt proceeds as quickly as possible. A pale brownish coloured mixture of benzene, benzophenone and aromatic products first distils over. The distillation is stopped when the distillate becomes brown and viscous. The distillate is dried with calcium chloride, and then fractionated. The fraction 250-310° C contains the benzophenone. The product sometimes solidifies quickly, but more frequently remains syrupy for days. Crystallisation begins, however, at once, when a small quantity of solid benzophenone is added. The crystals are freed from the oily mother liquor by pressing between filter paper, or by spreading on a porous tile, and are recrystallised from ligroin. Yield 30% theoretical (2 g).

Systematic organic chemistry, by W. M. Cumming, 93, 1937.





InChI Key


Canonical SMILES


MeSH Synonyms


Depositor-Supplied Synonyms

BENZOPHENONE, Diphenyl ketone, diphenylmethanone, Benzoylbenzene, 119-61-9, Phenyl ketone, Methanone, diphenyl-, Ketone, diphenyl, Benzene, benzoyl-, alpha-Oxoditane, diphenyl-methanone, alpha-Oxodiphenylmethane, Diphenylketone, .alpha.-Oxoditane, Caswell No. 081G, NSC 8077, WLN: RVR, .alpha.-Oxodiphenylmethane, phenylketone, UNII-701M4TTV9O, CCRIS 629, FEMA No. 2134, CHEBI:41308, HSDB 6809, RWCCWEUUXYIKHB-UHFFFAOYSA-N, EINECS 204-337-6, SBB040865, EPA Pesticide Chemical Code 000315, NCGC00090787-05, AI3-00754, DSSTox_CID_1961, DSSTox_RID_76429, DSSTox_GSID_21961, CAS-119-61-9, Benzophenon, Kayacure bp, meta-benzophenone, Diphenyl-methanon, 1dzp, Ph2CO, Adjutan 6016, PubChem20909, ACMC-20aj4t, AC1Q5CWD, UPCMLD-DP071, AC1L1F6B, BENZOPHENONE (8CI), BIDD:PXR0008, SCHEMBL17745, KSC174M3P, MLS001055400, BIDD:ER0022, CHEMBL90039, W213403_ALDRICH, 427551_ALDRICH, 442842_SUPELCO, 701M4TTV9O, UPCMLD-DP071:001, 73664_FLUKA, CTK0H4637, FEMA 2134, TIMTEC-BB SBB040865, NSC8077, MolPort-000-872-026, OTAVA-BB 1043895, HMS2268A24, LABOTEST-BB LTBB001874, 239852_SIAL, NSC-8077, AKOS BBS-00004333, METHANONE, DIPHENYL- (9CI), Tox21_113465, Tox21_202425, Tox21_300058, LS-619, STL363250, ZINC00968233, AKOS000119029, Tox21_113465_1, AS01184, BENZOPHENONE (DIPHENYL-KETONE), DB01878, EBD2761160, MCULE-7496069620, NE10260, RP24333, RTR-023462, TRA0083729, NCGC00090787-01, NCGC00090787-03, NCGC00090787-04, NCGC00090787-06, NCGC00090787-07, NCGC00090787-08, NCGC00254183-01, NCGC00259974-01, AN-43310, BP-21212, KB-75396, SMR000112143, ZB015526, AB1002070, DB-061602, B0083, FT-0622720, FT-0693251, ST50214455, C06354, 3B4-3247, I14-8023, T7103995, 3B3-033050, METTLER-TOLEDO(R) CALIBRATION SUBSTANCE ME 18870, Mettler-Toledo(R) Calibration substance ME 18870, Benzophenone, InChI=1/C13H10O/c14-13(11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10, 3-((R)-1-(2,6-dichloro-3-fluorophenyl)ethoxy)-5-(1-(piperidin-4-yl)-1H-pyrazol-4-yl)pyridin-2-amine, 852361-03-6

Removed Synonyms

Crizotinib, CID3102, C047723, 877399-52-5, BPN, BZQ


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