Molecular formula. C₁₆H₂₁NO₃,HBr

Relative molecular mass. 356.3

Graphic formula.

Chemical name. 1αH,5αH-Tropan-3α-ol mandelate (ester) hydrobromide; (±)-endo-8-methyl-8-azabicyclo[3.2.1]oct-3-yl α-hydroxybenzeneacetate hydrobromide; CAS Reg. No. 51-56-9.

Description. Colourless crystals or a white, crystalline powder; odourless.

Solubility. Freely soluble in water; sparingly soluble in ethanol (~750 g/l) TS; practically insoluble in ether R.

Category. Mydriatic.

Storage. Homatropine hydrobromide should be kept in a tightly closed container, protected from light.

Requirements

Definition. Homatropine hydrobromide contains not less than 98.5% and not more than 101.0% of C₁₆H₂₁NO₃,HBr, calculated with reference to the dried substance.

Identity tests

A. Dissolve 10 mg in 1 mL of water, add ammonia (~100 g/l) TS to render the solution slightly alkaline, and shake with 5 mL of chloroform R. Evaporate the chloroform layer to dryness on a water-bath and add 1.5 mL of mercuric chloride/ethanol TS to the residue; a yellow colour is produced, which turns red on heating.

B. A 20 mg/mL solution yields reaction A described under 2.1 General identification tests as characteristic of bromides.

C. Melting temperature, about 215°C with decomposition.

Sulfated ash. Not more than 1.0 mg/g.

Loss on drying. Dry to constant weight at 105°C; it loses not more than 15 mg/g.

pH value. pH of a 20 mg/mL solution, 5.5-7.0.

Foreign alkaloids. Dissolve 10 mg in 2 mL of water and add 0.25 mL of tannic acid (50 g/l) TS; no precipitate is produced.

Related alkaloids. Dissolve 5 mg in 0.25 mL of fuming nitric acid R and evaporate to dryness on a water-bath. Allow to cool, add 0.1 mL of acetone R and 0.1 mL of a mixture of 1 volume of potassium hydroxide/ethanol (0.5 mol/l) VS and 4 volumes of aldehyde-free ethanol (~750 g/l) TS; no violet or reddish violet colour is produced.

Assay.

Dissolve 0.300 g in a mixture of 5.0 mL of hydrochloric acid (0.01 mol/L) VS and 50 mL of dehydrated ethanol R. Carry out a potentiometric titration using sodium hydroxide (0.1 mol/L) VS, as described under 2.6 Non-aqueous titration. Read the volume added between the two points of inflexion.

1 mL of sodium hydroxide (0.1 mol/L) VS is equivalent to 35.63 mg of C₁₆H₂₁NO₃,HBr.