B. Cocaine
Synonyms 2β-Carbomethoxy-3β-benzoxytropane; l-Cocaine; β-Cocaine; Benzoylmethylecgonine; Ecgonine methyl ester benzoate.
Biological Sources It is obtained from the leaves of Erythroxylon coca Lam. and other species of Erythroxylon, (Erythroxylaceae); and leaves of Erythroxylon truxillense Rusby (Erythroxylaceae).
Chemical Structure
[IR-(exo, exo]-3-(Benzoyloxy)-8-methyl-8-azabicyclol [3, 2, 1] octane-2-carboxylic acid methyl ester; (C17H21NO4).
Isolation Cocaine is extracted from the plant by digestion either with sodium carbonate solution or with lime water and by subsequent solvent extraction using petroleum ether (bp 160-180°C; or 200-220°C). The combined petroleum ether extract is shaken up with dilute HCl. The solution of hydrochloride thus obtained is concentrated carefully in a thin-film evaporator. In case, the leaves are rich in cocaine content, as in the Peruvian coca leaves, a major portion of cocaine gets separated as crystals.
Characteristic Features
1. Cocaine is obtained as the monoclinic tablets from ethanol having mp 98°C.
2. It usually becomes volatile above 90°C; however, the resulting sublimate is not crystalline in nature.
3. Its physical parameters are as follows; bp0.1, 187-188°C; [α]D18 -350 (50% ethanol); [α]D20 -160 (C = 4 in chloroform); pKa (15°C) 8.61 and pKb (15°C) 5.59.
4. Solubility Profile: 1 g of cocaine dissolves in 600 ml of water; 270 ml of water at 80°C; 6.5 ml of ethanol; 0.7 ml of chloroform; 3.5 ml of ether; 12 ml of turpentine; 12 ml of pure olive oil; and 30-50 ml of liquid petrolatum. It is also soluble in acetone, carbon disulphide and ethyl acetate.
Identification Tests
1. Cocaine Permanganate: The addition of a drop of saturated solution of KMnO4 to a solution of cocaine prepared in a saturated solution of alum gives rise to a violet crystalline precipitate due to the formation of cocaine permanganate. It clearly shows characteristic violet aggregates of plates when examined under the microscope.
2. Cocaine Hydrochloride (C17H21NO4.HCl) (Cocaine Muriate): It is obtained as granules, crystals, or powder. It has a slightly bitter taste and usually numbs lips and tongue. Its physical characteristics are: mp ~ 195°C; [α]D – 72° (C = 2 in aqueous solution); 1 g dissolves in 0.4 ml of water; 3.2 ml cold and 2 ml hot alcohol; 12.5 ml chloroform. It is also soluble in glycerol and acetone; and insoluble in ether or oils.
3. Cocaine Nitrate Dihydrate (C17H22N2O7.2H2O): Its crystals have mp 58-63°C. It is freely soluble in water or ethanol; and slightly soluble in ether.
4. Cocaine Sulphate (C17H21NO4.H2SO4): It is obtained as white, crystalline or granular powder, which is soluble in ethanol and water.
Uses
1. It is used as a local anaesthetic as it causes numbness.
2. Its main action is a CNS-stimulant and, therefore, categorized as ‘narcotic drugs’. It is a highly habit-forming drug.
