Synthesis of 2-benzoylbenzoic acid

Preparation of 2-benzoylbenzoic acid (o-benzoylbenzoic acid; benzophenone-2-carboxylic acid)

Preparation of 2-benzoylbenzoic acid (o-benzoylbenzoic acid; benzophenone-2-carboxylic acid)

Preparation of 2-benzoylbenzoic acid (o-benzoylbenzoic acid; benzophenone-2-carboxylic acid)

The Friedel and Crafts reaction is carried out in a 500 ml round-bottomed flask equipped with a short condenser. A trap for collecting the hydrogen chloride liberated is connected to the top of the condenser by means of a piece of rubber tubing sufficiently long to make it possible to heat the flask on the or to plunge it into an ice bath. The most convenient form of trap is a suction flask half-filled with water and with a delivery tube inserted to within 5 mm of the surface of the water. 15 grams of phthalic anhydride and 75 ml of thiophene free benzene are placed in the flask and this is cooled in an ice bath until the benzene begins to crystallize. 30 grams of anhydrous aluminum chloride are added, the condenser and trap are connected, and the flask is shaken well and warmed for a few minutes by the heat of the  hand. If the reaction does not start, the flask is warmed very gently. At the first sign of vigorous boiling or evolution of hydrogen chloride, the flask is held over the ice bath in readiness to immerse in ice if the reaction becomes too vigorous. This gentle, cautious heating is continued until the reaction is proceeding smoothly enough so that the mixture may be refluxed by heating. The refluxing is continued for one-half hour with constant stirring. It is generally noted that, after about 5 minutes of refluxing, the aluminum chloride nearly all dissolves and the colorless addition product suddenly separates. At the end of the time specified the flask is cooled well in ice and the aluminum compound is decomposed by the cautious addition of ice and then water. While shaking the flask in the ice bath, small pieces of ice are added, one at a time waiting after each addition until the last piece has reacted. Too rapid addition of ice may cause very vigorous boiling. When the ice no longer produces much reaction and about 100 ml has been added, 20 ml of concentrated hydrochloric acid are added, together with enough water to make the flask half full. The excess benzene is then removed by steam distillation, and it is separated from the water layer. The 2-benzoylbenzoic acid is left as an oil which partially solidifies on cooling in ice. The aqueous solution containing aluminum chloride is decanted through a suction funnel, the residue is washed once with water, and the material collected is returned to the flask. In order to remove traces of aluminum, the acid is dissolved in sodium carbonate solution. This is done by adding 75 ml of 10% sodium carbonate solution and enough water to half fill the flask, and then passing in steam as in a steam distillation until all of the solid material except particles of aluminum oxide or aluminum hydroxide has become dissolved. The solution of the sodium salt of 2-benzoylbenzoic acid is then cooled well in ice, stirred with 1 g of activated charcoal, filtered by suction, and placed in a 600 ml beaker. The acid is then precipitated by cautious neutralization with hydrochloric acid, adding a little at a time and stirring well. The 2-benzoylbenzoic acid usually separates as an oil, but it soon solidifies on stirring and cooling. The material obtained in this way consists largely of the rather unstable monohydrate, which melts at 94.5° C. For the preparation of pure, anhydrous 2-benzoylbenzoic acid acid the still moist precipitate of the crude hydrate is transferred to a 250 ml flask, 125 ml of ordinary benzene is added, and the mixture is heated. After the 2-benzoylbenzoic acid has dissolved in the benzene the mixture is transferred to a separatory funnel and the aqueous layer is drawn off and extracted with 25 ml of benzene. The combined benzene solutions are placed in a dry 250 ml Erlenmeyer flask and 2-3 g of activated charcoal is added. The benzene need not be dried since the charcoal absorbs the small amount of water present. The solution is boiled for 2-3 minutes, filtered, and concentrated to a volume of 50-60 ml. Ligroin is added slowly to the hot solution until a slight turbidity is produced, and at this point crystals begin to separate. After spontaneous cooling to room temperature, and then in an ice bath to 5° C, the colorless, well formed crystals are collected and dried. The yield is 17-20 grams or 74-88%; The melting point of anhydrous 2-benzoylbenzoic acid acid 127-128° C.

Experiments in Organic Chemistry, L. F. Fieser, 184-187, 1941


2-benzoylbenzoic acid



InChI Key


Canonical SMILES


MeSH Synonyms

2-benzoylbenzoic acid

Depositor-Supplied Synonyms

2-BENZOYLBENZOIC ACID, 85-52-9, o-Benzoylbenzoic acid, Benzophenone-2-carboxylic acid, Benzoic acid, 2-benzoyl-, 2-Carboxybenzophenone, Benzoic acid, o-benzoyl-, o-Carboxybenzophenone, Benzophenone-2-carbonic acid, 2-Benzoquinonecarboxylic acid, 2-BenzoYl-Benzoic Acid, Ortho-benzoylbenzoic acid, BENZOYLBENZOIC ACID, 2-(phenylcarbonyl)benzoic acid, NSC 6646, SKP 10A, CHEMBL196812, HSDB 5249, FGTYTUFKXYPTML-UHFFFAOYSA-N, EINECS 201-612-2, BRN 1107841, AI3-15222, 27458-06-6, benzoyl benzoic acid, o-benzoyl benzoic acid, o-benzoyl-benzoic acid, 2-benzoyl benzoic acid, PubChem20125, Benzoic acid, benzoyl-, AC1Q5UTK, 16463-33-5, ACMC-209q6h, AC1L1ND1, Oprea1_391180, SCHEMBL76332, B12385_ALDRICH, KSC206I7R, UNII-1N20Y812XW, AC1Q723L, IFLab1_004537, RARECHEM AL BO 1426, 12928_FLUKA, CTK1A6478, TIMTEC-BB SBB016647, 1-carboxy-2-phenylcarbonylbenzene, NSC6646, ORTHO-BENZOYL BENZOIC ACID, MolPort-000-679-611, 1N20Y812XW, BB_SC-0111, HMS1424O05, NSC-6646, AKOS BBS-00000803, ANW-38199, AR-1D9086, BBL007937, LABOTEST-BB LT01143281, LABOTEST-BB LT03328148, LABOTEST-BB LT03333255, SBB016647, STK387490, AKOS000118995, AC-2859, AS00732, CCG-202854, MCULE-6199465138, RP27653, RTR-031103, IDI1_010292, OTAVA-BB 7020401721, AJ-14942, AK114318, AN-13525, KB-68165, LS-36099, AB1002798, TR-031103, B0103, BB 0220554, EU-0033235, FT-0611294, ST24022007, ST50211380, T8228, 4-10-00-02977 (Beilstein Handbook Reference), AG-205/01795007, I14-14206, 3B3-034751, InChI=1/C14H10O3/c15-13(10-6-2-1-3-7-10)11-8-4-5-9-12(11)14(16)17/h1-9H,(H,16,17

Removed Synonyms

batimastat, CID6813, 130370-60-4, 88327-91-7

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