Thursday, 16 July 2009

Monographs: Pharmaceutical substances: Benzylis benzoas - Benzyl benzoate

Molecular formula. C14H12O2

Relative molecular mass. 212.3

Graphic formula.

Chemical name. Phenylmethyl benzoate; CAS Reg. No. 120-51-4.

Description. A clear, colourless, oily liquid; odour, faintly aromatic.

Miscibility. Practically immiscible with water and glycerol R; miscible with ethanol (~750 g/l) TS and ether R.

Category. Scabicide (topical use).

Storage. Benzyl benzoate should be kept in a tightly closed and well-filled container, protected from light.

Additional information. Benzyl benzoate may slowly decompose on contact with air.


Definition. Benzyl benzoate contains not less than 98.0% and not more than 100.5% of C14H12O2.

Identity tests

Boil 2 g with 25 ml of potassium hydroxide/ethanol TS2 for 10 minutes, evaporate the ethanol on a water-bath, cool, extract with 2 successive quantities, each of 15 ml of ether R, and proceed as follows:

A. Evaporate the ethereal layer on a water-bath; heat 1 drop of the oily liquid with 5 ml of sodium carbonate (50 g/l) TS and 1 ml of potassium permanganate (0.02 mol/l) VS; an odour of benzaldehyde is discernible.

B. To the aqueous layer add 10 ml of sulfuric acid (~100 g/l) TS; a white, crystalline precipitate is produced. Wash and dry the precipitate; melting temperature, about 123°C (benzoic acid).

Congealing temperature. Not below 17.0°C.

Refractive index.

Mass density. ρ20 = 1.116 - 1.120 g/ml.

Chlorinated compounds. For the preparation of the test solution dissolve 0.30 g in 15 ml of ethanol (~750 g/l) TS and add 6 ml of sodium hydroxide (~80 g/l) TS. Warm the solution for 5 minutes on a water-bath. Cool, transfer to a comparison tube, and add 3 ml of nitric acid (~130 g/l) TS. For the reference solution transfer separately 2.0 ml of hydrochloric acid CITS and 4 ml of nitric acid (~130 g/l) TS to a comparison tube, and dilute to 25 ml with water. To both tubes add 0.5 ml of silver nitrate (40 g/l) TS. Stir immediately with a glass rod and set aside for 5 minutes, protected from direct sunlight. The opalescence produced from the test liquid is not stronger than that produced from the reference solution; not more than 0.33 mg/g of chlorine.

Acidity. Add 5 ml of the test liquid to 5 ml of neutralized ethanol TS, and titrate with carbonate-free sodium hydroxide (0.1 mol/l) VS, phenolphthalein/ethanol TS being used as indicator; not more than 0.3 ml is required to obtain the midpoint of the indicator (pink).

Assay. Add about 2.0 g, accurately weighed, to 40 ml of potassium hydroxide/ethanol (0.5 mol/l) VS and boil under reflux for 1 hour. Cool, and titrate with hydrochloric acid (0.5 mol/l) VS, using phenolphthalein/ethanol TS as indicator. Repeat the operation without the test liquid being examined and make any necessary corrections. Each ml of potassium hydroxide/ethanol (0.5 mol/l) VS is equivalent to 106.1 mg of C14H12O2.

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