Organic Syntheses, Coll. Vol. 2, p.53 (1943); Vol. 13, p.4 (1933).
Five hundred grams of castor oil (Note 1)
is added to a solution of 100 g. of potassium hydroxide
in 1 l. of 95 per cent alcohol
. The mixture is placed in a 3-l. flask
equipped with a reflux condenser
and is boiled for three hours. The solution is then poured into 3 l. of water and acidified by the addition of a solution of 100 cc. of concentrated sulfuric acid
in 300 cc. of water. The acid which separates is washed twice with warm water, shaken intermittently for one hour with 100 g. of anhydrous magnesium sulfate
, and then filtered with suction. The yield of crude ricinoleic acid
thus obtained is 480 g.
The acid should be oxidized at once (Note 2)
Two hundred and forty grams (0.8 mole) of the dried ricinoleic acid
is dissolved in 1.6 l. of water containing 64 g. of potassium hydroxide
. A 12-l. round-bottomed flask
is equipped with a powerful mechanical stirrer
, and in it are placed 625 g. (3.5 moles) of potassium permanganate
and 7.5 l. of water at 35°. The mixture is stirred to facilitate solution of the permanganate, and, if necessary, heat is applied to maintain the temperature at 35°. When the permanganate has completely dissolved, the alkaline solution of ricinoleic acid
is added in a single portion with vigorous stirring (Note 3)
. The temperature rises rapidly to about 75°. Stirring is continued for a half hour, or until a test portion added to water shows no permanganate color.
The oxidation mixture is now divided into two equal portions and each portion is treated as follows: To the mixture is added a solution of 200 g. of concentrated sulfuric acid
in 600 cc. of water (Note 4)
. The mixture is heated on a steam bath
for 15 minutes to coagulate the manganese dioxide
which is filtered while still very hot (Note 5)
. After filtration the manganese dioxide
is placed in a 4-l. beaker
and boiled with 2 l. of water to dissolve any azelaic acid
that may adhere to it. This mixture is filtered while hot, and the filtrate is added to the main portion.
The combined filtrates and washings for the two portions of the oxidation mixture are evaporated to a volume of about 4 l., and this solution is cooled in ice. The crystals which separate are filtered with suction, washed once with cold water, and dried. The yield is 70–80 g. of material having a melting point that may vary from 95 to 105°.
The crude substance is dissolved in 1.2 l. of boiling water, filtered with suction, and allowed to cool. The crystals are filtered, washed with water, and dried. There is obtained 48–55 g.
of product (32–36
per cent of the theoretical amount, based upon the amount of crude ricinoleic acid
taken for oxidation). The melting point of the purified azelaic acid
The castor oil used was a commercial grade designated as "Crystal." It was obtained from the Baker Castor Oil Company, New York City.
If ricinoleic acid
is allowed to stand, polymerization occurs; Baker and Ingold report1
that the polymerized acid gives very poor yields in the oxidation by nitric acid
At this point the mixture tends to froth quite badly, and, if stirring is not vigorous, material may be lost. Addition of a small quantity of ether or benzene
may be resorted to but is unnecessary if stirring is efficient.
The acid must be added slowly and carefully to prevent too rapid evolution of carbon dioxide
with consequent foaming. If possible, each of the two portions should be placed in a large container
, such as a 12-l. flask.
For this purpose it is advisable to use three 20-cm. Büchner funnels
supported in 2-l. filter flasks
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