Page 239 - Chemical and process design handbook

Speight_Part II_C 11/7/01 3:08 PM Page 2.179

COCAINE

o
Cocaine (melting point: 79 C) and similar alkaloids are extracted commer-
cially by alkalizing the ground leaves of the coca plant with a 10% sodium
carbonate solution and percolating countercurrently in large steel percolators,
using kerosene or toluene. The total alkaloids are extracted from the kerosene
or toluene by a process that blows them up with a 5% sulfuric acid solution in
tanks. The extracted kerosene or toluene is returned to the percolators. From
the sulfuric acid solution, the mixed alkaloids are precipitated by alkalizing
with sodium carbonate. The precipitated crude alkaloids are slowly boiled in
an 8% sulfuric acid solution for several days to split all the alkaloids to ecgo-
nine. During the splitting, many of the organic acids, like benzoic, are
partly volatilized from the kettle with the steam. Those acids that are still
suspended and those that crystallize out on cooling are filtered off. The
acid aqueous solution of ecgonine is neutralized with potassium carbonate
and evaporated. The low-solubility potassium sulfate is filtered hot, and
cooling causes the ecgonine to crystallize. After drying, it is methylated,
using methanol and 92% sulfuric acid, filtered, and washed with alcohol.
The methylecgonine sulfate is benzoylated to cocaine in a very vigorous
reaction with benzoyl chloride in the presence of anhydrous granular
potassium carbonate. The cocaine is extracted from the potassium salts
with ether and removed from the ether by sulfuric acid extraction, precip-
itated with alkali, and crystallized from alcohol. To form the hydrochlo-
ride, an alcoholic solution is neutralized with acid alcohol (hydrogen
chloride dissolved in absolute ethyl alcohol), and the cocaine hydrochlo-
ride is crystallized.
Because of decreased demand, cocaine is also obtained as a by-product
in the preparation of a decocained extract of Erythroxylon coca, this being
one of the principal flavors of cola beverages. The procedure is to alkalize
the Erythroxylon coca and extract all the alkaloids with toluene. The deco-
cainized leaf is dried and extracted with sherry wine to give the flavoring
extract.

2.179